Routes of Administration

Various routes of drug administration in pharmacology with their advantages and disadvantages.

1. Routes of Administration Prepared by Ms. Nisha S. Mhaske M.Pharm (Q.A.T) Lecturer, PRES’s COPD, Chincholi. Email : [email protected] Loknete Dr.Balasaheb Vikhe Patil ( Padmabhushan Awardee ) Pravara Rural Education Society’s College of Pharmacy (D.Pharm) Nashik.

2. Contents Introduction to ROA Factors affecting on ROA First pass effect Types of ROA- Enteral , Parenteral References

3. A ROA is a way of getting a drug onto/into the body. Factors influencing the ROA Ease of administration Site of action Onset of action Duration of action Quantity of drug Site of action Choice of ROA is influenced by desired site of action. The term local use refers to site specific application of drugs. The term systemic use refers to the application of a drug to the site of action by absorption into the blood & subsequent transportation throughout the body. even a drugs meant for systemic administration are usually targeted to a specific site of action.

4. Onset of action Liquid solution or suspensions work faster and readily available for absorption than oral tablets or capsules. Tablet placed under tongue or between cheeks and gums work quickly because, these medication bypasses stomach and liver, goes directly into bloodstream. Drugs injected/infused directly goes into bloodstream are carried immediately throughout the body. Topical medications works quickly, localized therapeutic effects Eg -applied to the skin, inhaled into the lungs, instilled into the eye.

5. Duration of action Is the length of time a drug gives the desired responses or is at the therapeutic level. Quantity of drug Tablet-containing a lot of filler (diluents) & small amount of drug IV infusion-is an excellent method for systemic delivery of large quantities of material & rapidly diluted in the bloodstream. Injections & infusions can deliver higher dose to the target site.

6. First pass effect Is also called as Pre-systemic metabolism. It is the extent to which a drug is metabolized by the liver before reaching into the systemic circulation. Metabolism of drug before reaching to the systemic circulation. The four primary systems that affect the first pass effect of a drug are the:- Enzymes of the gastrointestinal Lumen. Gut wall enzymes Bacterial enzymes Hepatic enzymes. This  first pass  through the liver thus greatly reduces the Bioavailability of the drug.

7. Routes of Administration Enteral (Alimentary canal) Parenteral (other than Alimentary canal) Oral Eg - Tablet, capsule Injections Intravenous (IV) Intramuscular (IM) Intradermal (ID) Subcutaneous (SC) Intra-arterial (IA) Intra-articular (IA) Intra-peritoneal (IP) Intra-thecal (IT) Intra-medullary Induction Iontophoresis Jet injection ii. Buccal & sublingual Eg - Glyceryl trinitrite tablet ii. Inhalations Eg - Isoprenaline spray iii. Rectal Eg - Suppositories iii. Local Application(Topical) Eg -ointment, paste. iv. Nasogastric

8. Oral route In this route, the drug is placed in oral cavity & is swallowed along with water / milk. Eg -Tablet, Capsule, Suspension, Emulsion Advantages Disadvantages It is a common & safe route Onset of action is slow Special skill is not required Absorption of certain drugs irregular & negligible It is very convenient route Not useful in clinical emergencies Sterilization is not required Irritant & unpalatable drugs can not be administered by this route Low possibilities of adverse reactions Not useful in unconscious & uncooperative patients Applicable from infants up to aged patients Not useful in prevomitting & diarrhea patients. 100% Bioavailability is not possible by this route. Large quantity of drugs can be administered Presence of food in GIT may interfere with absorption of drugs. Oral administration of some drugs may disturb micro flora of GIT Accurate blood levels of the drug can not be maintained by this route. (due to 1 st pass effect )

9. Sublingual route In this route, tablet is placed below the tongue and allowed to dissolve in mouth cavity. The active drug get absorbed through the sublingual mucus membrane directly into blood circulation. Eg-i. Isoprenaline tablet for- Bronchial asthma ii. Glyceryl trinitrite for- Angina pectoris . Advantages Disadvantages Rapid onset of action Not suitable for large doses & frequent use of drug Degradation of drug is avoided in stomach Some drug may cause irritation to buccal mucosa Avoid first pass effect Excessive salivation may cause swallowing of drug If tablet is found to be toxic, it can be spit out easily. The drugs having direct or toxic effects should be administered carefully to side effects in heart. Presence of food in GIT does not affect the absorption of drug

10. Rectal route The drug in the form of solution is introduced into the rectum is called rectal route. Eg - enema preparations, suppository. Advantages Disadvantages When the drug produces irritation by oral route, this route may used Absorption of drug is not complete because less surface area is available for absorption Patient unable to swallow drug then This route is not liked by the patients Children who do not cooperate in taking medicines by oral route then Few drug may produce local irritation of anal mucosa When local effects in the rectum are required. Possibility of absorption of drug into blood & drug may be metabolized in the liver before reaching the target organ.

11. Nasogastric Nasogastric  intubation is a medical process involving the insertion of a plastic tube ( nasogastric   tube or NG tube ) through the nose, pass the throat, and down into the stomach. A nasogastric tube is used for feeding and administering drugs .

12. Parenteral Route The drug administration is carried out other than alimentary canal are called as parenteral routes. The drug is in the form of solution or suspension is injected in the body with the help of hollow needle & syringe. In some cases, drugs in the form of vapor or fine droplets are inhaled in respiratory tract . Advantages Disadvantages Rapid onset of action Route is inconvenient for frequent administration of the drugs The drugs which irritate GIT, can be given by this route Skilled person is necessary Accurate dose & accurate blood level of drug can be possible Strict aseptic techniques is to be followed during drug administration Useful in case of vomiting & diarrhea The possibility of pain & edema at the site of application Useful in unconscious & uncooperative patients Self medication is difficult Small quantity of drug is required by this route (Large quantity of drug can be given as an saline formulation) Sterilization of syringe & needle is necessary Useful in clinical emergencies Possibility of nerve damage 100% bioavailability is possible by IV route Once the drug is absorbed in blood circulation, the adverse effects can not be reversed & controlled.

13. Intravenous route In this route, the drug is directly injected into the lumen of vein. The drug produces rapid action & desired blood concentration can be achieved by a definite dose of a drug.

14. Advantages Disadvantages Onset of action is very fast Self medication is difficult Effective in clinical emergencies Sometimes, leakage of drug outside the vein produces severe irritation & abscess formation 100% absorption of drugs Sterilization of syringe & needle is essential Small as well as large quantity of drug can be administered by this route. Eg. Normal saline solution Skilled person is essential for drug administration Hypertonic solutions can be given by IV because the drug is diluted by bloodstream Speed of drug entering through IV set should be slow & constant supervision is necessary Complete bioavailability of drug can be assured by IV route. Once the drug is absorbed in blood circulation, the adverse effects can not be reversed & controlled. Adjustment of additional dose & control on the rate of administration is possible by IV route

15. Intramuscular route In this route, the drug is directly injected into the muscular tissue. Eg -colloids & injections with insoluble oil bases

16. Advantages Disadvantages Mild irritants Sterilization of syringe & needle is essential Absorption of water soluble drugs is rapid Skilled person is required Massaging & application of heat at the site of injection by IM route may increase the drug absorption Some drugs may cause tissue irritation & pains It gives prolonged duration of action Chances of nerve damage Total volume of drug injected by IM route is restricted up to 10 ml. Certain IM injections require more time for absorption as compared to oral route

17. Intradermal route Drug is injected into the dermis layer of skin. Only a small quantity of drug can be administered by this route Injection is painful. Importance This route is used for the detection of drug allergy Eg -penicillin is injected intradermally to observe allergic reactions to it. Vaccines such as BCG, smallpox are administered by this route.

18. Subcutaneous route Subcutaneous (SC) injections are administered into the adipose tissue layer just below the epidermis and dermis. Dose should be not more than 1.5 ml to avoid pressure on sensory nerves causing pain & discomfort.

19. Intra-arterial route Intra-arterial drug  injection  or  infusion  is a  method  of delivering a drug directly into artery or arteries to localize its  effect to a particular organ/body region. The method is considered more dangerous than   intravenous administration. This route is rarely used by the surgeon for tracing or relieving certain arterial diseases. Very risky Eg - Anticancer drugs are given by this route for localized effect.

20. Intra articular route A joint injection ( intra - articular  injection) is a procedure used in the treatment of inflammatory joint conditions, such as rheumatoid arthritis, psoriatic arthritis, gout, tendinitis, bursitis, Carpal Tunnel Syndrome, and occasionally osteoarthritis. Eg - Hydrocortisone Tendinitis- inflammation of tendon Bursitis- inflammation of the fluid-filled sacs in the joints. Gout- deposition of sodium crystals in joints.

21. Intra peritoneal route Injected into peritoneal cavity

22. Intra- thecal Intrathecal  administration is a route of administration for drugs via an injection into the spinal canal, or into the subarachnoid space so that it reaches the cerebrospinal fluid (CSF) and is useful in spinal anaesthesia , chemotherapy, or pain management applications.

23. Intramedullary/BMI(Bone Marrow Injections) Administration of a drug within the marrow cavity of a bone.  When veins are not available Response is rapid. Intracameral injections Drug is injected into the eye ball. Intracardiac Adrenaline is injected into the heart during an extreme emergency.

24. . Jet injection It involves transcutaneous introduction of a drug by a high velocity jet produced through a micro fine orifice. It does not require a needle & is suitable for mass inoculation. Eg-Insulin jet injections are now available.

25. Iontophoresis Iontophoresis , also known as Ionization, is a physical process in which ions/drug flow diffusively in a medium driven by the use of an electric current.

26. Inhalations In this route, the drug in the form of gas or in vapors form can be inhaled. Eg - Isoprenaline spray is used in bronchial asthma. Volatile general anesthetics are also given by this route. Advantages Disadvantages The absorption of drug by this route is very rapid The drug directly enters the left side of the heart, hence there is a danger of cardiac toxicity. The drug given by this route produces local as well as systemic effects Certain drugs produce local irritation, may increase respiratory secretions. Blood levels of volatile substances such as anesthetics can be conveniently controlled. Special apparatus such as atomizer or nebulizer is needed for administration of drug.

27. Local application/topical route In this route, the drugs are applied or administered to the localized or specific areas of the body. These preparations are to be meant for their action at the site of application. Eg - Ointment, Paste, Drops, Lotions. Advantages Disadvantages This route provides an easy administration of drug The drugs in the form of watery solution are sometimes absorbed into the blood & may produce undesirable effects. Local application is useful when prolonged effect of drug is required The drugs like eye drops may penetrate into the anterior chamber & affect ciliary muscles. Eg.cocaine There is a low possibility of systemic absorption of the medicament. Some drugs may show toxic effect at the site of application. No special skill or apparatus is required for administration.

28. References Pharmacology & Toxicology, by V.N.Raje , 2 nd edition, CBS publishers & distributors pvt.ltd. Pharmacology & toxicology, by Kale & Kale, Nirali prakshan . Introduction to Pharmacology, by Dandiya & Kulkarni , Vallabh Prakashan . Elementary Pharmacology & Toxicology, by R.D.Bhudhiraja , Popular prakashan . Textbook of pharmacology, by FSK Barar , S.chand prakashan . Essentials of Medical pharmacology, K.D.Triphati .

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