Ointments

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These are semisolid preparations of drugs, either dispersed or
dissolved in a suitable base, meant for application to the skin or
mucous membranes.
ADVANTAGES
  • Handling of ointments is easier than bulky liquid dosage forms.
  • They are chemically more stable than liquid dosage forms.
  • They facilitate application of the directly to the effected body part and avoid exposure of other parts to the drug.
  • They are suitable for patients who find it difficult to take the drugs by parenteral and oral routes.
  • They prolong the contact time between the drug and effected area.
  • The bioavailability of drugs administered as ointments is more since it prevents passage through liver.
DISADVANTAGES
  • They are bulkier than solid dosage forms.
  • When applications of an exact quantity of ointment to the affected area is required, it is difficult to ascertain the same.
  • They are less stable than solid dosage forms.
The various types of ointments are
  • Medicated ointments
  • Unmedicated ointments
MEDICATED OINTMENTS
These ointments contain drugs which show local or systemic effects. These are of several sub-types
  • Dermatologic ointments
  • Opthalmic ointments
  • Rectal ointments
  • Vaginal ointments
  • Nasal ointments
DERMATOLOGIC OINTMENTS
These ointments are applied topically on the external skin. The
ointment is applied to the affected area as a thin layer and spread
evenly using gentle pressure with the fingertips.These are of three
types
(1) Epidermic ointments: The drugs present in these type of ointments exert their action on the epidermis of the skin.
Example: Ketoconazole ointment.
(2) Endodermic ointments: The drugs present in these types of
ointments exert their action on the deeper layers of cutaneous tissue.
Example: Demodex ointment.
(3) Diadermic ointments: The drugs present in these types of
ointments enter into the deeper layers of skin and finally in the
systemic circulation and exert systemic effects.
Example: Nitroglycerine ointment.
OPTHALMIC OINTMENTS
These are sterile preparations which are applied inside the lower
eye lid. Only anhydrous bases are used in their preparation. The
ointment is applied as a narrow band of approximately 0.25 - 0.5 inch.
Example: Sulfacetamide sodium ointment.
RECTAL OINTMENTS
These are the ointments to be applied to the perianal or within
the anal canal. The bases used are combinations of PEG 300 and PEG
3350, cetyl alcohol and cetyl esters, wax, liquid paraffin and white
paraffin.
Example: Benzocaine ointment.
VAGINAL OINTMENTS
These ointments are applied to the vulvovaginal area or inside the
vagina. As vagina is more susceptible to infections, the ointment
should be free from micro-organisms, moulds and yeasts.
Example: Candicidin ointment.
NASAL OINTMENTS
These are used in the topical treatment of nasal mucosa. Drugs get
absorbed into the general circulation through the rich blood supply of
the nasal lining.
Example: Ipratropium bromide ointment.
UNMEDICATED OINTMENTS
These ointments donot contain any drugs. They are useful as emollients, protectants or lubricants.
Example: Petroleum jelly.
CLASSIFICATION OF OINTMENT BASES
Four different classes of bases are available
  • Hydrocarbon or oleaginous bases
  • Absorbent bases
  • Emulsion bases
  • Water-soluble bases
HYDROCARBON BASES: These are semisolid hydrocarbons obtained from petroleum.
Examples: Hard paraffin, yellow soft paraffin, white soft petroleum and gelled oleaginous vehicle.
ABSORBENT BASES: These are hydrophilic mixtures
of hydrocarbons and substances with polar groups. Substances like
cholesterol, lanolin, lanosterol etc., may be used in the formation of
absorption bases.
Examples: Hydrophilic petrolatum, hydrous wool fat and oily cream.
EMULSION BASES: These are miscible with water and
contain oil-in-water emulgents. They can be easily removed from the
skin. They contain surfactants which serve the purpose of emulgents.
Based on the nature of surfactant present, emulsion bases are of three types.
(a) Anionic emulsion bases: contains anionic surfactants like sodium lauryl sulphate.
Examples: Hydrophilic ointment and emulsifying ointment.
(b) Cationic emulsion bases: contains cationic surfactants like cetrimide.
Example: Cetrimide emulsifying ointment.
(c) Non-ionic emulsion bases: contains nonionic surfactants like cetomacrogols.
Examples: Cetomacrogol emulsifying wax.
WATER - SOLUBLE BASES: They donot contain oily ingredients and are called greaseless bases. They are completely soluble in water.
Examples: Polyethylene glycols (PEGs), polyoxyl 40 stearate, and polysorbates.
REFERENCES
  • "Dispensing pharmacy", R.M. Mehta, pg 217-230.
  • L. Lachman, H.A, Lieberman and J.L. Kanig, Theory & Practice of
    industrial pharmacy, Lea & Febieger, Philadelphia Latest Edn

About the Author

M Leela Keerthi's picture
Author: M Leela Keerthi

Comments

Amol Malpani's picture

Dear Leela, can you put some light on recent advances in ointments? Regards,

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