Types of tablets

types of tablets, parenteral forms, contact lenses

1. Types of Tablets
The various types of tablets are described as follows:
(A) Tablets ingested orally:
1. Compressed tablet, e.g. Paracetamol tablet
2. Multiple compressed tablet
3. Delayed release tablet, e.g. Enteric coated Bisacodyl tablet
4. Sugar coated tablet, e.g. Multivitamin tablet
5. Film coated tablet, e.g. Metronidazole tablet
6. Chewable tablet, e.g. Antacid tablet
(B) Tablets used in oral cavity:
1. Buccal tablet, e.g. Vitamin-c tablet
2. Sublingual tablet, e.g. Vicks Menthol tablet
3. Troches or lozenges
4. Dental cone
(C) Tablets administered by other route:
1. Implantation tablet
2. Vaginal tablet, e.g. Clotrimazole tablet
(D) Tablets used to prepare solution:
1. Effervescent tablet, e.g. Dispirin tablet (Aspirin)
2. Dispensing tablet, e.g. Enzyme tablet (Digiplex)
3. Hypodermic tablet
4. Tablet triturates e.g. Enzyme tablet (Digiplex)

(A)
1. Compressed tablets: Standard uncoated tablets are manufactured by compression.
The general methods are by wet granulation, dry granulation or direct compression, used
for rapid disintegration and drug release. Both type of action – systemic effect and local
effect.
In addition to the medicinal agent or agents, compressed tablets usually contain a
number of pharmaceutical adjuncts, including the following:
1. Diluents or fillers, which add the necessary bulk to a formulation to prepare
tablets of the desired size.
2. Binders or adhesives, which promote adhesion of the particles of the formulation,
allowing a granulation to be prepared and maintaining the integrity of the final tablet.
3. Disintegrants or disintegrating agents, which promote breakup of the tablets after
administration to smaller particles for ready drug availability.
4. Antiadherents, glidants, lubricants, or lubricating agents, which enhance the flow
of the material into the tablet dies, minimize wear of the punches and dies, prevent fill
material from sticking to the punches and dies, and produce tablets with a sheen.
5. Miscellaneous adjuncts such as colorants and flavorants.
After compression, tablets may be coated with various materials as described later.
Tablets for oral, buccal, sublingual, or vaginal administration may be prepared by
compression.

2. Multiple compressed tablets: Multiply compressed tablets are prepared by
subjecting the fill material to more than a single compression. The result may be a
multiple-layer tablet or a tablet within a tablet, the inner tablet being the core and the
outer portion being the shell. Layered tablets are prepared by initial compaction of a
portion of fill material in a die followed by additional fill material and compression to
form two-layered or three-layered tablets, depending on the number of separate fills.
Each layer may contain a different medicinal agent, separated for reasons of chemical or
physical incompatibility, staged drug release, or simply for the unique appearance of the
layered tablet. Usually, each portion of fill is a different color to produce a distinctive-
looking tablet. Examples include Norgesic Tablets (3M).

2. 3. Delayed action and enteric-coated tablet: This dosage form is intended to
release the drug after some time delay or after the tablet has passed one part of the GIT
into another. All enteric coated tablets are type of delayed action tablet but all delayed
action tablets are not enteric or not intended to produce enteric action. Enteric-coated
tablets are designed to pass unchanged through the stomach to the intestines, where the
tablets disintegrate and allow drug dissolution and absorption and/or effect. Enteric
coatings are employed when the drug substance is destroyed by gastric acid or is
particularly irritating to the gastric mucosa or when bypass of the stomach substantially
enhances drug absorption. Examples include Ecotrin Tablets and Caplets (SmithKline
Beecham).

4. Sugar coated tablet: Compressed tablets may be coated with a colored or an
uncolored sugar layer. The coating is water soluble and quickly dissolves after
swallowing. The sugar coat protects the enclosed drug from the environment and
provides a barrier to objectionable taste or odor. The sugar coat also produces an
elegant, glossy, and widely utilized in preparing multivitamin and multivitamin mineral
combination. Sugar coating doubled the tablet weight. Now polymers are used with
sugar solution.

5. Film coated tablet: One type of coated tablet in which drug is not required in
coating. This is an attractive method within one or two hours. Polymers such as hydroxyl
propyl cellulose, hydroxyl propyl methyl cellulose, and colloidal dispersion of ethyl
cellulose are commonly used in forming a skin like film. A 30% dispersion of ethyl
cellulose is known as aqua coat. The film is usually colored and has the advantage over
sugar coatings in that it is more durable, less bulky, and less time-consuming to apply.
By its composition, the coating is designed to rupture and expose the core tablet at the
desired location in the gastrointestinal tract.

6. Chewable tablet: These are intended to be chewed in the mouth before swallowing.
Chewable tablets, which have a smooth, rapid disintegration. These have a creamy base,
usually of specially flavored and colored mannitol. Chewable tablets are especially useful
for administration of large tablets to children and adults who have difficulty swallowing
solid dosage forms. Examples include Pepcid Chewable Tablets (J & J Merck), antacids
and Rolaids Chewable Tablets (McNeil)

Gelatin Coated tablets: A recent innovation is the gelatin-coated tablet. The
innovator product, the gel cap, is a capsule-shaped compressed tablet that allows the
coated product to be about one-third smaller than a capsule filled with an equivalent
amount of powder. The gelatin coating facilitates swallowing, and gelatin-coated tablets
are more tamper evident than unsealed capsules. Examples include Extra Strength
Tylenol PM Gel caps (McNeil-CPC).

Instantly disintegrating Or Dissolving tablets: Instant-release tablets (rapidly
dissolving tablets or RDTs) are characterized by disintegrating or dissolving in the
mouth within 1 minute, some within 10 seconds (e.g., Claritin Reditabs [loratadine],
Schering). Tablets of this type are designed for children and the elderly or for any patient
who has difficulty in swallowing tablets. They liquefy on the tongue, and the patient
swallows the liquid.

(B)
1. Buccal and sublingual tablet: Buccal and sublingual tablets are flat, oval tablets
intended to be dissolved in the buccal pouch (buccal tablets) or beneath the tongue
(sublingual tablets) for absorption through the oral mucosa. Drugs used by this route are
for quick systematic action. They enable oral absorption of drugs that are destroyed by

3. the gastric juice and/or are poorly absorbed from the gastrointestinal tract. Buccal
tablets are designed to erode slowly, whereas those for sublingual use (such as
nitroglycerin) dissolve promptly and provide rapid drug effects. Lozenges or trochesare
disc-shaped solid dosage forms containing a medicinal agent and generally a flavoring
substance in a hard candy or sugar base. They are intended to be slowly dissolved in the
oral cavity, usually for local effects, although some are formulated for systemic
absorption. An example would be Mycelex Troches (Bayer).

2. Troches and lozenges: Used in the oral cavity to exert local effect in mouth and
throat. They are commonly used to treat sore throat or to control coughing in common
cold. They may contain local anesthetics, antiseptic, antibacterial agents, demulcents,
astringent and antitussive. The tablets are dissolving slowly over a period of 30 minutes.
Dental cone: These tablets are designed to be placed in the empty socket remaining after
tooth extraction. Main purpose is to prevent microbial growth in the socket or to reduce
bleeding.

(C)
Implantation tablets: designed for substances implantation to provide prolonged
drug effect from one month to a year, tablets are usually small, cylindrical not more than
8mm length. These methods require special surgical technique for implantation and
discontinuation of therapy. Generally used for administration of growth hormone to food
producing animal.
Vaginal tablets: These are designed to undergo slow dissolution and drug release in
vaginal cavity. Tablets are wide or pear shaped, used to antibacterial, antiseptic and
astringent to treat vaginal infection.

(D)
1. Effervescent tablets: Effervescent tablets are prepared by compressing granular
effervescent salts (active ingredient with mixture of organic acid such as citric acid or
tartaric acid and sodium bicarbonate) that release gas when in contact with water. These
tablets generally contain medicinal substances that dissolve rapidly when added to water
and produce a solution rapidly with the release of carbon dioxide. The “bubble action”
can assist in breaking up the tablets and enhancing the dissolution of the active drug.
Examples include Alka-Seltzer Original and Extra-Strength Tablets (Bayer) and Zantac
EFFER dose (GlaxoSmithKline).

2. Dispersing tablets: Dispensing tablets are no longer in use. They might better have
been termed compounding tablets because the pharmacist used them to compound
prescriptions; they were not dispensed as such to the patient. Tablets are intended to be
added to a given volume of water to produce a solution of a given drug concentration.

3. Hypodermic tablets: These tablets are composed of one or more drugs with water-
soluble ingredients. Drug is added to sterile water to prepare sterile solution, which is
injectable.

4. Tablet triturates: Tablet triturates are small, usually cylindrical, molded or
compressed tablets containing small amounts of usually potent drugs. Such tablet must
be completely and rapidly soluble. Today, only a few tablet triturate products are
available commercially, with most of these produced by tablet compression. Since tablet
triturates must be readily and completely soluble in water, only a minimal amount of
pressure is applied during their manufacture. A combination of sucrose and lactose is
usually the diluent. The few tablet triturates that remain are used sublingually, such as
nitroglycerin tablets.

4. PARENTRAL DOSAGE FORM

DEFINITION
Parenteral preparations are sterile preparations intended for administration by injection,
infusion or implantation into the human or animal body. The term parenteral derives from the
Greek word in which Para means outside and Enteron means intestine. It denotes that route
of administration other than oral route.
ADVANTAGES
 It provides rapid onset of action
 It provides immediate therapeutic action
 It can be administered accurate dose
 It can be given to patients who cannot take oral medication
 It minimize the first pass effect
 It provides more bioavailability
DISADVANTAGES
 It should be administered aseptically
 It produces pain at the site of injection
 The administered of drug through wrong route may prove fatal effect
 Self-administration is not possible
 Pyrogenic preparations lead to very harmful effect.
ROUTES OF ADMINISTRATION
Routes of administration are Intra Muscular (IM), Intra dermal (ID), Intravenous (IV),
Subcutaneous / Hypodermic (SC), Intra articular, Intra synovial, Intra spinal, Intrathecal,
Intrarterial, Intra cardiac, Intra cisternal, Intra peritoneal and Intraplueral.
CRITERIA FOR PARENTRALS
Parenteral preparations may require the use of excipients, for example to make the
preparation isotonic with blood, to adjust the pH, to increase solubility, to prevent
deterioration of the active substances or to provide adequate antimicrobial properties but not
to adversely affect the intended medicinal action of the preparation or, at the concentrations
used, to cause toxicity or undue local irritation.
CONTAINERS AND CLOSURES
Containers for parenteral preparations are made as far as possible from materials that are
sufficiently transparent to permit the visual inspection of the contents, except for implants
and in other justified and authorized cases. Where applicable, the containers for parenteral
preparations comply with the requirements for Materials used for the manufacture of
containers and Containers. Parenteral preparations are supplied in glass containers or in
other containers such as plastic containers and prefilled syringes for e.g. Ampoules (single
dose), Vials (multiple dose), Cartridges, Automatic injector, etc. The tightness of the
container is ensured by suitable means. Closures ensure a good seal, prevent the access of
micro-organisms and other contaminants and usually permit the withdrawal of a part or the
whole of the contents without removal of the closure. The plastic materials or elastomers of
which the closure is composed are sufficiently firm and elastic to allow the passage of a
needle with the least possible shedding of particles. Closures for multidose containers are
sufficiently elastic to ensure that the puncture is resealed when the needle is withdrawn.
TYPES OF PARENTERALS
Several categories of parenteral preparations may be distinguished:
— Injections,
1. Injectable emulsion E.g. Propofol USP
2. Injectable suspension E.g. Methylprednisolone acetate
3. Oily injection (solution) E.g. Dimercaprol injection
— Infusions,
— concentrates for injections or infusions,
— powders for injections or infusions E.g. Cefuroxime for injection
— Implants.

5. PRODUCTION OF PARENTRALS
During the development of a parenteral preparation, the formulation for which contains an
antimicrobial preservative, the effectiveness of the chosen preservative shall be
demonstrated to the satisfaction of the competent authority. A suitable test method together
with criteria for judging the preservative properties of the formulation are provided under
Efficacy of antimicrobial preservation. Parenteral preparations are prepared using materials
and methods designed to ensure sterility and to avoid the introduction of contaminants and
the growth of micro-organisms; recommendations on this aspect are provided in the text on
Methods of preparation of sterile products. Water used in the manufacture of parenteral
preparations complies with the requirements of water for injections in bulk stated in the
monograph on Water for injections.
STORAGE
Store in a sterile, air tight or tamper-proof container.
LABELLING
The label states:
— The name and concentration of any added antimicrobial preservative,
— Where applicable, that the solution is to be used in conjunction with a final filter,
— Where applicable, that the preparation is free from bacterial endotoxins or that it is
apyrogenic.

INJECTIONS
DEFINITION & DESCRIPTION
Injections are sterile solutions, emulsions or suspensions. They are prepared by dissolving,
emulsifying or suspending the active substance(s) and any added excipients in Water for
injections, in a suitable, sterile non-aqueous liquid or in a mixture of these vehicles. Solutions
for injection, examined under suitable conditions of visibility, are clear and practically free
from particles. Emulsions for injection do not show any evidence of phase separation.
Suspensions for injection may show a sediment which is readily dispersed on shaking to
give a suspension which remains sufficiently stable to enable the correct dose to be
withdrawn.
Multidose aqueous injections contain a suitable antimicrobial preservative at an appropriate
concentration except when the preparation itself has adequate antimicrobial properties.
When it is necessary to present a preparation for parenteral use in a multidose container, the
precautions to be taken for its administration and more particularly for its storage between
successive withdrawals are given.
Aqueous preparations which are prepared using aseptic precautions and which cannot be
terminally sterilized may contain a suitable antimicrobial preservative in an appropriate
concentration.
No antimicrobial preservative is added when:
— The volume to be injected in a single dose exceeds 15 ml, unless otherwise justified,
— The preparation is intended for administration by routes, where, for medical reasons, an
antimicrobial preservative is not acceptable, such as intra cisternally, epidurally, intrathecally
or by any route giving access to the cerebrospinal fluid, or intra- or retro-ocularly. Such
preparations are presented in single-dose containers.
PRODUCTION
In the manufacture of injections containing dispersed particles, measures are taken to
ensure a suitable and controlled particle size with regard to the intended use.
Single-dose preparations. The volume of the injection in a single-dose container is sufficient
to permit the withdrawal and administration of the nominal dose using a normal technique.

INFUSIONS
DEFINITION & DESCRIPTION
Infusions are sterile, aqueous solutions or emulsions with water as the continuous phase;
they are usually made isotonic with blood. They are principally intended for administration in
large volume. Infusions do not contain any added antimicrobial preservative.

6. Solutions for infusion, examined under suitable conditions of visibility, are clear and
practically free from particles. Emulsions for infusion do not show any evidence of phase
separation.
PRODUCTION
In the manufacture of infusions containing dispersed particles, measures are taken to ensure
a suitable and controlled particle size with regard to the intended use. The volume of the
infusion in the container is sufficient to permit the withdrawal and administration of the
nominal dose using a normal technique.

CONCENTRATES FOR INJECTIONS OR INFUSIONS
DEFINITION
Concentrates for injections or infusions are sterile solutions intended for injection or infusion
after dilution. They are diluted to a prescribed volume with a prescribed liquid before
administration. After dilution, they comply with the requirements for injections or for
infusions.

POWDERS FOR INJECTIONS OR INFUSIONS
DEFINITION & DESCRIPTION
Powders for injections or infusions are solid, sterile substances distributed in their final
containers and which, when shaken with the prescribed volume of a prescribed sterile liquid,
rapidly form either clear and practically particle-free solutions or uniform suspensions. After
dissolution or suspension, they comply with the requirements for injections or for infusions.
Freeze-dried products for parenteral use are considered as powders for injections or
infusions.
PRODUCTION
The uniformity of content and uniformity of mass of freeze-dried products for parenteral use
are ensured by the in-process control of the amount of the solution prior to freeze-drying.
LABELLING
The label states the instructions for the preparation of injections and infusions.
IMPLANTS
DEFINITION
Implants are sterile, solid preparations of a size and shape suitable for parenteral
implantation and release the active substance(s) over an extended period of time. Each
dose is provided in a sterile container.

PATCHES, TRANSDERMAL
DEFINITION & DESCRIPTION
Transdermal patches are flexible pharmaceutical preparations of varying sizes, containing
one or more active substances. They are intended to be applied to the unbroken skin in
order to deliver the active substance(s) to the systemic circulation after passing through the
skin barrier.
Transdermal patches normally consist of an outer covering which supports a preparation
which contains the active substance(s). The transdermal patches are covered on the site of
the release surface of the preparation by a protective liner, which is removed before applying
the patch to the skin.
The outer covering is a backing sheet impermeable to the active substance(s) and normally
impermeable to water, designed to support and protect the preparation. The outer covering
may have the same dimensions as the preparation or it may be larger. In the latter case the
overlapping border of the outer covering is covered by pressure-sensitive adhesive
substances which assure the adhesion of the patch to the skin. The preparation contains the
active substance(s) together with excipients such as stabilizers, solubilizers or substances
intended to modify the release rate or to enhance transdermal absorption. It may be a single
layer or multi-layer solid or semi-solid matrix, and in this case it is the composition and
structure of the matrix which determines the diffusion pattern of the active substance(s) to
the skin. The matrix may contain pressure-sensitive adhesives which assure the adhesion of

7. the preparation to the skin. The preparation may exist as a semi-solid reservoir one side of
which is a membrane which may control the release and the diffusion of the active
substance(s) from the preparation. The pressure-sensitive adhesive substances may, in this
case, be applied to some or all parts of the membrane, or only around the border of the
membrane of the outer covering. When applied to the dried, clean and unbroken skin, the
transdermal patch adheres firmly to the skin by gentle pressure of the hand or the fingers
and can be peeled off without causing appreciable injury to the skin or detachment of the
preparation from the outer covering. The patch must not be irritant or sensitizing to the skin,
even after repeated applications. The protective liner generally consists of a sheet of plastic
or metal material. When removed, the protective liner does not detach the preparation
(matrix or reservoir) or the adhesive from the patch. Transdermal patches are normally
individually enclosed in sealed sachets.
PRODUCTION
In the manufacture, packaging, storage and distribution of transdermal patches suitable
means are taken to ensure their microbial quality; recommendations on this aspect are
provided in the text on Microbiological quality of pharmaceutical preparations (5.1.4).
STORAGE
Store at room temperature, unless otherwise indicated.
LABELLING
The label states, where applicable, the total quantity of active substance(s) per patch, the
dose released per unit time and the area of the releasing surface.

POWDERS FOR CUTANEOUS APPLICATION
DEFINITION & DESCRIPTION
Powders for cutaneous application are preparations consisting of solid, loose, dry particles of
varying degrees of fineness. They contain one or more active substances, with or without
excipients and, if necessary, coloring matter authorized by the competent authority. Powders
for cutaneous application are presented as single-dose powders or multidose powders. They
are free from grittiness. Powders specifically intended for use on large open wounds or on
severely injured skin are sterile.
Multidose powders for cutaneous application may be dispensed in sifter-top containers,
containers equipped with a mechanical spraying device or in pressurized containers.
Powders dispensed in pressurized containers comply with the requirements of Pressurized
pharmaceutical preparations.

EVALUATION TEST FOR PARENTRALS
 Test for pyrogen
 Sterility testing
 Clarity test
 LAL test
 Leaker test

8. CONTACT LENSES AND C ARE AND USE SOLUTION S
The number of persons wearing contact lenses grows each year, currently estimated to be
over 30 million. About 87% of these persons utilize soft, hydrogel lenses while the remainder
use rigid lenses (Rigid gas permeable [RGP]) with varying degrees of oxygen permeability.
Over 50% of contact lens wearers use 1- to 2-week disposable lenses and 15% use extended
wear (up to 30 days). To counsel patients properly, it is important for pharmacists to know
the characteristics and features of the types of contact lenses and the products available for
their care and use.
TYPES OF LENSES ON T HE BASIS OF MATERIAL
The three basic types of contact lenses are classified by their chemical composition and
physical properties as hard, soft, and RGP.
1. HARD CONTACT LENS ES provide durability and clear, crisp vision. The lenses are
termed hard because they are made of a rigid plastic resin, polymethyl methacrylate
(PMMA). The lenses are 7 to 10 mm in diameter and are designed to cover only part of the
cornea. They float on the tear layer overlying the cornea. Hard lenses require an adaption
period sometimes as long as a week for comfort. Even then, because of their rigidity, some
patients find them difficult to wear. PMMA lenses are practically impermeable to oxygen and
moisture (they absorb only about 0.5% water), a disadvantage to corneal epithelial
respiration and to comfort. Care must be exercised to prevent the hard lens from resting
directly on the corneal surface and causing physical damage to epithelial tissue. To prevent
direct contact, solutions are used to wet the lens and provide a cushioning layer between the
corneal epithelium and the inner surface of the lens.
PRODUCTS FOR HARD CO NTACT LENSES
Cleaners
Hard lenses should be cleaned immediately after removal from the eye. Otherwise, oil
deposits, proteins, salts, cosmetics, tobacco smoke, and airborne contaminants can build up,
interfere with clear vision, and possibly cause irritation upon reinsertion. A surfactant
cleaner is used by applying the solution or gel to both surfaces of the lens and then rubbing
the lens in the palm of the hand with the index finger for about 20 seconds. Too vigorous
rubbing can scratch or warp the lens.
Soaking and Storage Solutions
Hard lenses are placed in a soaking solution once they are removed from the eye. Soaking
solutions contain a sufficient concentration of disinfecting agent, usually 0.01%
benzalkonium chloride and 0.01% edetate sodium, to kill surface bacteria. Overnight soaking
is advantageous because it keeps the lenses wet and the prolonged contact time helps to
loosen deposits that remain after routine cleaning.
Wetting Solutions
Wetting solutions contain surfactants to facilitate hydration of the hydrophobic lens surface
and enable the tears to spread evenly across the lens by providing it with temporary
hydrophilic qualities. These solutions also provide a cushion between the lens and the cornea
and eyelid. Typical ingredients include a viscosity-increasing agent, such as hydroxyethyl
cellulose; a wetting agent, such as polyvinyl alcohol; preservatives, such as benzalkonium
chloride or edetate disodium; and buffering agents and salts to adjust the pH and maintain
tonicity.
Combination Solutions
Combination solutions mix effects, such as cleaning and soaking, wetting and soaking, or
cleaning, soaking, and wetting. While they are characterized by ease of use, combination
products may lower the effectiveness of cleaning if the concentration of cleaning solution is
too low to adequately remove debris from the lens. These combination solutions should be
reserved for wearers who have a demonstrated need for simplification of lens care.
2. SOFT CONTACT LENS ES are more popular than hard lenses because of their greater
comfort. They range from about 13 to 15 mm in diameter and cover the entire cornea.
Because of their size and coverage, soft lenses are less likely than hard lenses to dislodge
spontaneously. They also are less likely to permit irritating foreign particles (e.g., dust or
pollen) to lodge beneath them. However for some patients, soft lenses do not provide the

9. same high level of visual acuity as hard lenses. They are less durable than hard lenses and
carry some risk of absorbing medication concomitantly applied to the eye.
Soft contact lenses are made of a hydrophilic transparent plastic, hydroxyl ethyl
methacrylate, with small amounts of cross-linking agents that provide a hydrogel network.
Soft lenses contain 30% to 80% water, which enables enhanced permeability to oxygen.
There are two general types of soft contact lens: daily wear and extended wear. Whereas
daily wear lenses must be removed at bedtime, extended wear lenses are designed to be worn
for more than 24 hours, with some approved for up to 30 days of continuous wear. However,
it is advisable that lenses not be left in the eye for longer than 4 to 7 days without removal for
cleaning and disinfection; else the wearer can be predisposed to an eye infection.
Disposable soft lenses do not require cleaning and disinfection for the recommended
period of use; they are simply discarded and replaced with a new pair. Patients should be
advised to resist any temptation to wear the lenses for longer than recommended to avoid
risk of an eye infection.
PRODUCTS FOR SOFT CO NTACT LENSES
Cleaners
Because of their porous composition, soft lenses tend to accumulate proteinaceous material
that forms a film on the lens, decreasing clarity and serving as a potential medium for
microbial growth. The two main categories of cleaners are surfactants, which emulsify
accumulated oils, lipids, and inorganic compounds, and enzymatic cleaners, which break down
and remove protein deposits. Surfactant agents are used in a mechanical washing device, by
placing several drops of the solution on the lens surface and gently rubbing the lens with the
thumb and forefinger, or by placing the lens in the palm of the hand and rubbing gently with
a fingertip (about a 20- to 30-second procedure). The ingredients in these cleaners usually
include a nonionic detergent, wetting agent, chelating agent, buffers, and preservatives.
Enzymatic cleaning is accomplished by soaking the lenses in a solution prepared from
enzyme tablets. This procedure is recommended at least once a week or twice a month in
conjunction with regular surfactant cleansing. The enzyme tablets contain papain,
pancreatin, or subtilisin, which causes hydrolysis of protein to peptides and amino acids.
Typically, these are added to saline solution, but one solution can be prepared using 3%
hydrogen peroxide, which combines enzymatic cleaning with disinfection, that is, Ultrazyme
Enzymatic Cleaner. After the lenses have been soaked for the recommended time, they
should be thoroughly rinsed. This is important to do because a peroxide-soaked lens placed
directly into the eye will cause great pain, photophobia, redness, and possible corneal
epithelial damage.
Rinsing and Storage Solutions
Saline solutions for soft lenses should have a neutral pH and be isotonic with human tears,
that is, 0.9% sodium chloride. Besides rinsing the lenses, these solutions are used for
storage, because saline maintains their curvature, diameter, and optical characteristics. The
solutions also facilitate lens hydration, preventing the lens from drying out and becoming
brittle.
Because they are used for storage, some saline solutions contain preservatives, which
while inhibiting bacterial growth can induce sensitivity reactions or eye irritation. Thus,
some manufacturers make available preservative-free saline solutions and package them in
aerosol containers or unit-of-use vials. The use of salt tablets to prepare a normal saline
solution is discouraged because of the potential for contamination and risk of serious eye
infections.
Disinfection and Neutralization
Disinfection can be accomplished by either of two methods: thermal (heat) or chemical (no
heat). In the past, both methods were equally used; however, with the introduction of
hydrogen peroxide systems for chemical disinfection, has become more popular.
For thermal disinfection, the lenses are placed in a specially designed heating unit with
saline solution. The solution is heated sufficiently to kill microorganisms, perhaps for 10
minutes at a minimum of 80°C (176°F). It is important that after disinfection the lenses be
stored in the unopened case until ready to be worn. The wearer must also ensure that the

10. lenses have been thoroughly cleaned before using heat disinfection. Otherwise, heating can
hasten lens deterioration.
In years past, chemical disinfection was conducted with products that contained
thimerosal in combination with either chlorhexidine or a quaternary ammonium compound.
Unfortunately, many wearers had sensitivity reactions, and these products and chemical
disinfection fell into disfavor. The introduction of hydrogen peroxide systems for chemical
disinfection revitalized this method of disinfection. It is thought that the free radicals
chemically released from the peroxide react with the cell wall of the microorganisms, and the
bubbling action of the peroxide is thought to promote removal of any remaining debris on
the lens.
To prevent eye irritation from residual peroxide after disinfection, it is necessary that
the lenses be exposed to one of three types of neutralizing agents: the catalytic type (an
enzyme catalase or a platinum disk), the reactive type (such as sodium pyruvate or sodium
thiosulfate), or the dilution–elution type.
Chemical disinfection systems may come as two-solution systems, which use separate
disinfecting and rinsing solutions, or one-solution systems, which use the same solution for
rinsing and storage. It is important that the wearer realizes that lenses must not be
disinfected by heating when using these solutions.
3. RIGID GAS PERMEAB LE LENSES - RGP contact lenses take advantage of features
of both soft and hard lenses. They are oxygen permeable but hydrophobic. Thus, they permit
greater movement of oxygen through the lens than hard lenses while retaining the
characteristic durability and ease of handling. RGP lenses are more comfortable than hard
lenses. The basic type of lens is intended for daily wear; some of the newer super permeable
RGP lenses are suitable for extended wear.
There are advantages and disadvantages associated with each type of contact lens. Hard
contact lenses and RGP lenses provide strength, durability, and relatively easy care
regimens. They are easy to insert and remove and are relatively resistant to absorption of
medications, lens care products, and environmental contaminants. These lenses provide
visual acuity superior to that provided by soft contact lenses. On the other hand, hard contact
lenses and RGP lenses require a greater adjustment period for the wearer and are more
easily dislodged from the eye. Soft contact lenses have a shorter adaption period and may be
worn comfortably for longer periods. They do not dislodge as easily or fall out of the eye as
readily as the hard lenses. However, they have a shorter life span than hard or RGP lenses,
and the wearer must ensure that the lenses do not dry out.
PRODUCTS FOR RGP CON TACT LENSES
Care of RGP lenses requires the same general regimen as for hard contact lenses except that
RGP-specific solutions must be used. One of two cleaning methods, either hand washing or
mechanical washing, may be used. In the first method, the lens may be cleaned by holding
the concave side up in the palm of the hand. The lens should not be held between the fingers
because the flexibility of the lens may allow it to warp or turn inside out. Mechanical washing
is advantageous because the possibility of the lens turning inside out or warping during
cleaning is minimized.
After cleansing, the RGP lens should be thoroughly rinsed and soaked in a wetting or
soaking solution overnight. After overnight soaking, the lens is rubbed with fresh wetting or
soaking solution and inserted into the eye. To facilitate removal of stubborn protein deposits,
weekly cleaning with enzymatic cleaners is recommended.

TYPES OF LENSES ON T HE BASIS OF FUNCTION

CORRECTIVE CONTACT LENS
These are designed to improve vision by correcting refractive error.
1. Monovision lens.
2. Bifocal lens.

11. MONOVISION CONTACT L ENSES (POINTS)
 Single vision lens
 One eye for distance and other eye for near work
 Both eyes working together
 People adopt these lenses easily
 Less costly the bifocal lenses
BIFOCAL CONTACT LENS ES (POINTS)
 Two different prescriptions on the lens.
 One for close reading and other for distinct vision.
 Mostly used to treat presbyopia.

COLOR ADDITIVES TO C ONTACT LENSES
Contact lens manufacturers produce clear and colored lenses. The use of color additives in
medical devices, including contact lenses, is regulated by the U.S. Food and Drug
Administration (FDA) through authority granted by the Medical Device Amendments of
1976. Color additives that come into direct contact with the body for a significant period
must be demonstrated to be safe for consumer use. This includes the color additives used in
contact lenses. The FDA permits the use of a specific color additive in contact lenses only
after reviewing and approving a manufacturer’s official Color Additive Petition. The petition
must contain the requisite chemical, safety, manufacturing, packaging, and product labeling
information for FDA review. Many colored contact lenses are prepared as a reaction product,
formed by chemically bonding a dye, such as Color Index Reactive Red 180 (Ciba Vision) to
the vinyl alcohol–methyl methacrylate co polymeric lens material.

CARE OF CONTACT LENS ES
It is important that contact lenses receive appropriate care to retain their shape and optical
characteristics and for safe use. Wearers should be instructed in the techniques for insertion
and removal of the lenses in methods of cleaning, disinfecting, and storage.
With the exception of disposable soft contact lenses, all soft lenses require a routine
care program that includes (a) cleaning to loosen and remove lipid and protein deposits, (b)
rinsing to remove the cleaning solution and material loosened by cleaning, and (c)
disinfection to kill microorganisms. If the lenses are not maintained at proper intervals, they
are prone to deposit buildup, discoloration, and microbial contamination. The moist, porous
surface of the hydrophilic lens provides an attractive medium for the growth of bacteria,
fungi, and viruses. Thus, disinfection is essential to prevent eye infections and microbial
damage to the lens material.
Hard contact lenses require a routine care program that includes (a) cleaning to remove
debris and deposits from the lens, (b) soaking the lens in a storage disinfecting solution while
not in use, and (c) wetting the lenses to decrease their hydrophobic characteristics.
To achieve the care needs of contact lenses the following types of solutions are used: (a)
cleaning solutions, (b) soaking solutions, (c) wetting solutions, and (d) mixed-purpose
solutions.

Clinical Considerations in the Use of Contact Lenses
Although most medicated eye drops may be used in conjunction with the wearing of contact
lenses, some caution should be exercised and drug-specific information used, particularly
with soft contact lenses, because this type of lens can absorb certain topical drugs and affect
bioavailability.
Use of ophthalmic suspensions and ophthalmic ointments by contact lens wearers
presents some difficulties. The drug particles in ophthalmic suspensions can build up
between the cornea and the contact lens, causing discomfort and other undesired effects.
Ophthalmic ointments not only cloud vision but may discolor the lens. Thus, an alternative
dosage form, such as an ophthalmic solution, may be prescribed or lens wearing deferred
until therapy is complete.
Some drugs administered by various routes of administration for systemic effects can
find their way to the tears and produce drug–contact lens interactions. This may result in

12. lens discoloration (e.g., orange staining by rifampin), lens clouding (ribavirin), ocular
inflammation (salicylates), and refractive changes (acetazolamide). In addition, drugs that
cause ocular side effects have the potential to interfere with contact lens use. For example,
drugs with anticholinergic effects (e.g., antihistamines, tricyclic antidepressants) decrease
tear secretion and may cause lens intolerance and damage to the eye. Isotretinoin, prescribed
for severe, recalcitrant acne, can induce marked dryness of the eye and may interfere with
the use of contact lenses during therapy. Drugs that promote excessive lacrimation (e.g.,
reserpine) or ocular or eyelid edema (e.g., primidone, hydrochlorothiazide, and
chlorthalidone) also may interfere with lens wear.
Use of ophthalmic vasoconstrictors occasionally causes dilation of the pupil, especially
in people who wear contact lenses or whose cornea is abraded. Although this effect lasts only
1 to 4 hours and is not clinically significant, some patients have expressed concern. To allay
their concern, the FDA has recommended that patients be advised of this side effect by
product labeling stating PUPILS MAY BECOME DILATED (ENLARGED).
The following guidelines should be used by pharmacists in counseling patients: Contact
lens wearers should wash their hands thoroughly with a nonabrasive, noncosmetic soap
before and after handling lenses. Wearers should not rub the eyes when the lenses are in
place, and if irritation develops, the lenses should be removed until these symptoms subside.
Only contact lens care products specifically recommended for the type of lens worn
should be used. Also, to avoid differences between products of different manufacturers, it is
preferable to use solutions made by a single manufacturer. Cleaning and storing lenses
should be performed in the specific solution for that purpose. The patient should be
instructed to discard cleansers and other lens care products if the labeled expiration date is
exceeded. Lenses should not be stored in tap water, nor should saliva be used to help reinsert
a lens into the eye. Saliva is not sterile and contains numerous microorganisms, including P.
aeruginosa.
When handling a contact lens over the sink, the drain should be covered or closed to
prevent the loss of the lens. During cleansing, the patient should be advised to check the lens
for scratches, chips, and/or tears. Similarly, the lens should be inspected for any particulate
matter, particles, warpage, and/or discoloration. The patient must ensure the lens is cleaned
thoroughly and rinsed thoroughly. Otherwise, these factors can lead to eye discomfort and
irritation.
When cleaning a lens, the patient should be instructed to clean it back and forth and not
in a circular direction. To avoid the “left-lens syndrome,” the patient should be instructed to
clean the second lens as thoroughly as the first lens. Oftentimes, the right lens is removed
and cleaned first and the second less thoroughly, which will result in more deposits after
cleaning.
As appropriate, contact lens users should be counseled with regard to cosmetic use. It is
prudent to purchase makeup in the smallest container, because the longer a container is
open and the more its contents are used, the greater the likelihood of bacterial
contamination. Mascara and pearlized eye shadow should be avoided by women wearing
hard lenses because particles of these products can get into the eye and cause irritation, with
corneal damage a possibility. Aerosol hairsprays should be used before the lens is inserted
and preferably applied in another room, since airborne particles may attach to the lens
during insertion and cause irritation. Lenses should be inserted before makeup application
because oily substances on the fingertips can smudge the lenses when they are handled. For
similar reasons, lenses should be removed before makeup. Wearers of contact lenses
normally do not have ocular pain. If pain is present, it may be a sign of ill-fitting lenses,
corneal abrasion, or other medical condition, and the patient should be advised to consult
his or her ophthalmologist. Hard or soft contact lenses may occasionally cause superficial
corneal changes, which may be painless and not evident to the patient. Thus, it is important
that all contact wearers have their eyes examine regularly to make certain that no damage
has occurred.