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Terramycin Ophthalmic Ointment
Brand names: Terramycin Ophthalmic Ointment
Generic name: Oxytetracycline 0.5%, polymyxin B 10,000 u
Per g Oxytetracycline 0.5%, polymyxin B 10,000 u
Treatment of superficial ocular infections involving the conjunctiva and/or cornea (including keratitis and blepharitis) due to susceptible (gram-negative) microorganisms.
Topical application of Terramycin Ophthalmic Ointment should be supplemented with systemic administration when infections are severe or do not respond to topical therapy alone.
Terramycin Ophthalmic Ointment is administered as a small quantity (approximately 1 cm) of the ointment which should be instilled or applied into the conjunctival sac of the lower lid 4-6 times daily until the infection is cleared and healing is complete. This may take from 1 day to several weeks depending on the nature and severity of the infection. In blepharitis, scales and crusts should be removed before applying medication. For prophylaxis, the same procedure is followed on the day before operation and subsequently for several days following it. The patient should be instructed to avoid contamination of the tip of the tube when applying the ointment.
Persons who have shown hypersensitivity to any of the components of Terramycin Ophthalmic Ointment.
As with other antibiotic preparations, Terramycin Ophthalmic Ointment may result in overgrowth of nonsusceptible organisms including fungi. Constant observation of the patient is essential. If new infections due to nonsusceptible bacteria or fungi appear during therapy, appropriate therapy should be instituted as indicated by susceptibility testing.
Adverse Drug Reactions
Allergic reactions due to individual hypersensitivity have been reported. If reactions occur, therapy should be discontinued.
Each gram of ophthalmic ointment contains oxytetracycline 0.5% and polymyxin B 10,000 units in a sterile petrolatum base.
Oxytetracycline is a product of the metabolism of Streptomyces rimosus and is one of the family of tetracycline antibiotics. A 1% solution in water is acidic (pH about 2.5). Its potency is affected in solutions more acidic than pH 2 and it is rapidly destroyed by alkali hydroxides.
Oxytetracycline is 4-(dimethylamino)-1,4,4α,5,5α,6,11,12α-octahydro-3,5,6,10,12,12α-hexahydroxy-6-methyl-1,11-dioxo-2-naphthacenecarboxamide and has a molecular formula of C22H24N2O9. The molecular weight of oxytetracycline HCl is 496.90. It is odorless, bitter, yellow crystalline powder soluble in water. It forms a cloudy or turbid solution in water due to liberation of oxytetracycline base.
Polymyxin B sulfate is a white or buff-colored hygroscopic powder, odorless or with a slight odor. It is very soluble in water with a 2% solution producing a pH of 5-7.
1 mg of pure polymyxin B is equivalent to 10,000 units.
Mechanism of Action
Oxytetracycline is primarily bacteriostatic and is thought to exert its antimicrobial effect by the inhibition of protein synthesis.
Oxytetracycline is active against a wide range of gram-negative and gram-positive organisms.
The drugs in the tetracycline class have closely similar antimicrobial spectra, and cross-resistance among them is common.
Polymyxin B sulfate, one of a group of related antibiotics derived from Bacillus polymyxa, is rapidly bactericidal. This action is exclusively against gram-negative organisms. It is particularly effective against Pseudomonas aeruginosa and Haemophilus aegyptius frequently found in local infections of the eye.
There is, thus, made available a particularly effective antimicrobial combination of the broad-spectrum antibiotic Terramycin as well as polymyxin B sulfate against primarily causative or secondarily infecting organisms.