Ointment

Ointments are homogenous, translucent and viscous semi-solid preparation.

1. Ointment .

2. . Definition: Ointments are homogenous, translucent, viscous semi-solid preparations, most commonly a greasy, thick oil (oil 80% - water 20%) intended for external application to the skin or mucous membrane. They are used as e mollients , protective, therapeutic and prophylactic purpose.

3. Classification of Ointments: A- Epidermic ointments: • These ointments are intended to produce their action on the surface of the skin and produce local effect they are not absorbed. • They acts as protectives, antiseptics and parasiticides. B- Endodermic ointments: • These ointments are intended to release the medicaments that penetrate into the skin. They are partially absorbed and acts as emollients, stimulant and local irritants. C- Diadermic ointments: • These ointments are intended to release the medicaments that pass through the skin and produce systemic effects.

4. Types of base for ointments The USP recognizes four general classes of ointment bases to be used therapeutically or as vehicles for active ingredients: Hydrocarbon (oleaginous): Ex. White Petrolatum, White Ointment, Vaseline etc. Absorption : ( Anhydrous absorption and Water-in-oil emulsion): Ex.: Hydrophilic Petrolatum, Lanolin, Cold Cream, Rose Water Ointment etc. Water-miscible/removable : Ex.: Hydrophilic Ointment, Vanishing Cream etc. Water-soluble : Ex. Polyethylene Glycol ointment, polybase .

5. Selection of the Appropriate Base The selection of the base of an ointment depends on many factors: Patient Factors: Selection of base depends on the condition of the patient's skin, e.g. oozing or dry. If a patient's skin is dry, occlusive ointment base that retain moisture is preferable. Physicochemical Factors: The desired release rate of the drug from the ointment base. The desired enhancement of the percutaneous absorption of the drug.

6. . The desired occlusion of moisture from the skin by the base. The stability of the drug in the ointment base, for a drug that hydrolyzes rapidly as antibiotics, a hydrocarbon base would provide the greatest stability. The influence of the drug on the consistency of the ointment base. The desired wash ability of the base as for application to hairy regions, a Polyethylene Glycol base is preferred. For ophthalmic ointments, non-irritant bases are desired. Absorption O/W emulsion bases and water soluble bases are irritants due to the effect of the surfactants in the base. It is preferred to use yellow paraffin but not white due to the irritation effect of the bleaching agents.

7. Preparation of Ointments Ointments are prepared by three general methods: Incorporation method Fusion method Emulsification method

8. . 1. Incorporation method: The components of the ointment are mixed together by various means until a uniform preparation has been attained. On a small scale, the pharmacist may mix the components of an ointment in a mortar with a pestle, or a spatula and an ointment slab may be used to rub the ingredients together.

9. . 2. Fusion Methods: By the fusion method, all or some of the components of an ointment are combined by being melted together and cooled with constant stirring until congealed. Those components not melted are generally added to the congealing mixture as it is being cooled and stirred. Naturally, heat-labile substances and any volatile components are added last when the temperature of the mixture is low enough not to cause decomposition of volatilization of the components.

10. . 3. Emulsification method: In the preparation of ointments having an emulsion type of formula, the general method of manufacture involves a melting process as well as an emulsification process.

11. Evaluation of ointments Penetration Rate of release of medicament Absorption of medicament into blood stream Irritant effect

12. Penetration: Weighed quantities of the ointments are rubbed over definite areas of the skin for a given length of time. Thereafter the unabsorbed ointment is collected from the skin and weighed. The difference between the two weights roughly represents the amount absorbed ointment.

13. 2. Rate of release of medicament To assess rate of release of medicament, small amount of the ointment can be placed on the surface of nutrient agar contained in a Petri dish. If the medicament is bactericidal the agar plate is previously seeded with a suitable organism like s. aureus. After a suitable period of incubation, the zone of inhibition is measured and correlated with the rate of release. Smear internal surface of test tubes with thin layers of ointment, fill the tubes with saline/serum and after a gap of time estimating the amount of drug present in the serum/saline.

14. 3. Absorption of medicament into blood stream Definite amount of ointments should be rubbed through the skin. Under standard conditions and medicaments are estimated in the blood plasma or urine. 4 . Irritant effect The irritant effect can also be judged to a certain extent by injecting the ointment into thigh muscles and under the abdominal skin of rats. Reaction are noted at intervals of 24,48,72 and 96 hours. Presence of patches on the skin within 2 weeks indicate irritancy to pressing skin.

15. Difference between ointments and cream: . Ointment Contains more than 50% hydrocarbon and less than 20% of water Thicker consistency, greasy, difficult to spread over large areas of the skin Stay longer on the surface of skin, prescribed for dry skin, keeps moisture for a longer periods. Cream Contains less than 50% hydrocarbon and more than 20% of water Lighter in consistency, easy to spread over large areas of the skin Due to high water content skin dry up faster. Better for greasy/oily skin.

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