Survey of microbial contamination of ophthalmic ointments

Investigation of fatty acid esters to replace isopropyl myristate in the sterility test for ophthalmic ointments

Several pharmacopoeias recommend the membrane filtration method for the sterility test of ophthalmic ointments. Isopropyl myristate, a fatty acid ester that exhibits high toxicity mainly against Gram-negative microorganisms, is indicated as a solvent for ointments. In this study, six fatty acid esters (diethyl adipate, diisopropyl adipate, ethyl laurate, ethyl myristate, methyl caprylate and isopropyl palmitate) were evaluated as solvents to replace isopropyl myristate in the sterility test for ophthalmic ointments. The logarithm of the partition coefficient (logP) of the fatty acid esters was calculated from the sum of the substituent hydrophobicity constants (pi) of the functional groups present in their molecules. The ability of the solvents to dissolve an ophthalmic ointment base was investigated. The D-value method was used to assess the antimicrobial activity of isopropyl palmitate, ethyl myristate, ethyl laurate and isopropyl myristate against Pseudomonas aeruginosa. Isopropyl palmitate was the least toxic solvent to this microorganism, since it had the highest D-value (171.1 min). No significant difference was observed between the D-values of ethyl myristate (89.4 min) and isopropyl myristate (92.5 min). Ethyl laurate exhibited the lowest D-value (27.2 min). Using gas chromatography coupled to mass spectrometry, other fatty acid esters were detected as the predominant impurities in the solvents, as well as acid contaminants in low or insignificant amounts.

Type of closure prevents microbial contamination of cosmetics during consumer use

The dispensing closure used for containers plays an important role in protecting cosmetics from in-use microbial contamination. This hypothesis was tested by aseptically packing unpreserved shampoo and skin lotion into containers with three different closure types which provided various degrees of protection against consumer and environmental microbial insults. Shampoo was packed in containers with slit-cap (n = 25), flip-cap (n = 25), or screw-cap (n = 28) closures. Skin lotion was packed in containers with pump-top (n = 21), flip-cap (n = 18), or screw-cap (n = 21) closures. The products were then used by volunteers under actual in-use conditions for 3 (shampoo) or 2 (skin lotion) weeks. After use, the products were evaluated for microbial contamination by using standard methods for enumeration and identification. The standard screw-cap closure provided only minimal protection against microbial contamination of both the shampoo (29% contamination incidence) and the skin lotion (71%). The slit-cap closure on the shampoo container and the flip-cap closure on the skin lotion container provided slightly enhanced degrees of protection (21 and 39% contamination incidence, respectively). The greatest amount of protection (i.e., lowest contamination incidence) was provided by the flip-cap closure for the shampoo container (0%) and the pump-top closure for the skin lotion container (10%). As a result, closure type plays an important role in protecting poorly preserved products from in-use microbial contamination.

The ophthalmic rod: a new ophthalmic drug delivery system I

The ophthalmic rod (OR) is a new drug delivery system, intended as an alternative to conventional therapy in ophthalmology. The rod is made of a nontoxic plastic. It is dipped into a drug solution which after drying forms a thin homogeneous coating. The OR is then packed and sterilized by gamma radiation. The effects of radiation on the contents of the drugs were studied using IR, UV, and thin-layer chromatography (TLC). Sterility, dose variation, and simulated drug delivery in vitro were tested. Pure drugs were used; no preservatives were included. To deliver the drug, the tip of the rod is introduced into the conjunctival sac and rubbed against the palpebral conjunctiva of the lower lid. ORs with tropicamide, oxybuprocaine HCl, pilocarpine HCl, and fluorescein sodium were used. The behavior of the drugs administered by this system was compared with eyedrops. Results of trials with three drugs, i.e., tropicamide, oxybuprocaine HCl, and fluorescein sodium on ORs applied to the eyes of humans and those of the rabbit are discussed.

The ophthalmic rod--a new drug-delivery system II

The ophthalmic rod (OR) is a new ophthalmic drug-delivery system. The rod is made of nontoxic plastic. The active substance is deposited as a thin film on the end of the rod. To deliver the drug, the tip of the rod is introduced into the conjunctival sac and rubbed against the palpebral conjunctiva of the lower lid. The OR is a single-dose sterile applicator. By using the OR the problems of preservation and sterility of eyedrops are eliminated, and the risk of cross-infection is avoided. This was an open uncontrolled study. Clonidine ORs were used by 15 patients with glaucoma for 12 days. Fluorescein ORs were used for tonometry and to check the safetness of using the ORs. Patients with dry eyes or scotoma were excluded from the study. The clonidine film remaining on the ORs after delivery was quantitatively analyzed. A dose of 20 micrograms clonidine rod, three ORs/day, was sufficient to keep the ocular pressure under control. The fluorescin ORs, 30 micrograms/rod, were satisfactory for coloring the cornea. On the last day (12th) no clinically apparent side effects were observed. Subjectively, the patients were satisfied with the OR method of application, as an alternative to eyedrops.

Correlation of in vitro challenge testing with consumer use testing for cosmetic products

An in vitro microbial challenge test has been developed to predict the likelihood of consumer contamination of cosmetic products. The challenge test involved inoculating product at four concentrations (30, 50, 70, and 100%) with microorganisms known to contaminate cosmetics. Elimination of these microorganisms at each concentration was followed over a 28-day period. The test was used to classify products as poorly preserved, marginally preserved, or well preserved. Consumer use testing was then used to determine whether the test predicted the risk of actual consumer contamination. Products classified by the challenge test as poorly preserved returned 46 to 90% contaminated after use. Products classified by the challenge test as well preserved returned with no contamination. Marginally preserved products returned with 0 to 21% of the used units contaminated. As a result, the challenge test described can be accurately used to predict the risk of consumer contamination of cosmetic products.

Batch-swirl method for detoxification of isopropyl myristate used for sterility testing of oils and ointments: membrane selection

A 1-hr batch-swirl method was developed for the preparation of isopropyl myristate to be used in the sterility testing of oils and ointments. The method is simpler and faster than that in USP XX. Flow rates of various membrane filters were tested. Cellulose acetate filters increased the filtration rate of oils and ointments and, thus, reduced the exposure time of possible microbial contaminants to the toxicity of isopropyl myristate.

Ophthalmic ointments

The use of ointments as an ocular drug vehicle adds an important dimension to topical therapy. Ointments are well tolerated, fairly safe, and provide an excellent means for enhanced ocular contact time. In the case of certain antibiotics, this improved contact time yields increased ocular drug levels. However, experimental data indicate that corticosteroid ointments do not penetrate into the eye as well as do suspension preparations. This may relate to the binding of the drug to the ointment base and also to the particular steroid compound. Like other ophthalmic preparations, ointments may become contaminated. Ophthalmic ointments should not be instilled into eyes with open wounds. Instillation of ointments into postoperative eyes where wound closure is secure appears to be safe and effective.

The recovery of bacteria from white soft paraffin

Methods have been investigated for isolating and enumerating, by a membrane filtration technique, E. coli inoculated into white soft paraffin. Of three solvents used to prepare the ointment base for filtration, the best recovery (54%) was obtained with light liquid paraffin. Superior recovery levels (ca 75%) were obtained by homogenizing the ointment base with a Tween 80/peptone water mixture. Recovery levels were greatly affected by the weight of ointment base taken but the Tween 80/peptone water system permitted the estimation of the contamination in up to 0ṁ25 g of white soft paraffin.