Ofloxacin

METHOD OF PREPARATION

1. Calculate the required quantity of each ingredient for the total amount to be prepared.

2. Accurately weigh and/or measure each ingredient.

3. Pulverize the ofloxacin tablets to a very, very fine powder.

4. Add the glycerin and mix well.

5. Add the propylene glycol to volume and mix well.

6. Package and label.

PACKAGING

Package in tight, light-resistant containers.1

LABELING

Keep out of reach of children. Use only as directed. For external use only.

STABILITY

A beyond-use date of up to 60 days, when stored in a refrigerator, can be used.1

USE

Ofloxacin topical liquid is used in the treatment of superficial infections susceptible to the drug.

QUALITY CONTROL

Quality-control assessment can include weight/volume, specific gravity, active drug assay, color, rheological properties/ pourability, physical observation and physical stability (discoloration, foreign materials, gas formation, mold growth).2

DISCUSSION

Onflxacin is currently available as an ophthalmic solution, otic solution and as orally administered tablets, but not as a topical preparation.

Ofloxacin (C^sub 18^H^sub 20^FN^sub 3^O^sub 4^, MW 361.38) occurs as a pale yellowish-white to light yellowish-white crystals or crystalline powder. It is slightly soluble in alcohol and water. Commercial Floxin tablets include ofloxacin anhydrous lactose, cornstarch, hydroxypropyl cellulose, hydroxypropyl methylcellulose, magnesium stearate, polyethylene glycol, polysorbate 80, sodium starch glycolate, titanium dioxide and may contain synthetic yellow iron oxide.1,3

Glycerin (C^sub 3^H^sub 8^O^sub 3^, MW 92.1, glycerol, 1,2,3-propane triol) occurs as a clear, colorless, odorless, viscous, hygroscopic liquid with a sweet taste about 2/3 as sweet as that of sucrose. It is used as an antimicrobial preservative (>20% concentration), emollient and humectant (up to 30% concentration), in ophthalmic formulations (0.5-3% concentration), plasticizer in film coating for tablets, parenteral solvent (up to 50% concentration) and as a sweetening agent in alcoholic elixirs (up to 20% concentration). It has a specific gravity of about 1.25 and a melting point of 17.8°C; if cooled to crystallization, it will need to be heated to about 20°C to melt. It is miscible with water, methanol and 95% ethanol; practically insoluble in oils and chloroform and slightly soluble in acetone. It is hygroscopic and should be stored in airtight containers in a cool place. It is not prone to oxidation but will decompose on heating. When mixed with water, ethanol and propylene glycol, the mixtures are chemically stable. Incompatibilities include strong oxidizing agents, where it may explode, such as chromium trioxide, potassium chlorate, potassium permanganate. When mixed with zinc oxide or basic bismuth nitrate and exposed to light, it will form a black discoloration. When mixed with phenols, salicylates or tannin, a darkening of the mixtures may occur due to an iron contaminant in the glycerin. It will also form a strong acid complex, glyceroboric acid, when mixed with boric acid.4

Propylene glycol (C^sub 3^H^sub 8^O^sub 2^, MW 76.09) occurs as a clear, colorless, viscous, practically odorless liquid with a sweet taste, somewhat resembling glycerin. It has a specific gravity of 1.038 g/mL and is miscible with acetone, chloroform, 95% ethanol, glycerin and water. It is not miscible with fixed oils or light mineral oil. It will, however, dissolve some essential oils. A 2% v/v aqueous solution of propylene glycol will be iso-osmotic with serum. Propylene glycol is used as a humectant in topicals (~15% concentration), preservative in solutions and semisolids (15-30% concentration), as a solvent or cosolvent in aerosols (10-30% concentration), oral solutions (10-25% concentration), parenterals (10-60% concentration) and topicals (5-80% concentration). Propylene glycol is actually a better solvent than glycerin. It is similar to ethanol as an antiseptic and is also used in cosmetics and in the food industry as a vehicle for flavors and emulsiriers. It is stable and may be mixed with numerous other solvents. Aqueous solutions of propylene glycol can be sterilized by autoclaving. Since propylene glycol is hygroscopic, it should he stored in an airtight container and protected from light. Incompatibilities include potassium permanganate.5

REFERENCES

1. US Pharmacopeial Convention, Inc. United States Pharmacopeia 27-National Formulary 22. Rockville, MD: US Pharmacopeial Convention, Inc.; 2004: 2345-2349.

2. Allen LV Jr. Standard operating procedure for performing physical quality assessment of oral and topical liquids. IJPC 1999; 3: 146-147.

3. [No author listed.] Physicians' Desk Reference. 58th ed. Montvale, NJ: Medical Economics Company; 2004: 2439-2443.

4. Price JC. Glycerin. In: Rowe RC, Sheskey PJ, Weller PJ, eds. Handbook of Pharmaceutical Excipients. 4th ed. Washington, DC: American Pharmaceutical Association; 2003: 257-259.

5. Weller PJ. Propylene glycol. In: Rowe RC, Sheskey PJ, Weller PJ, eds. Handbook of Pharmaceutical Excipients. 4th ed. Washington, DC: American Pharmaceutical Association; 2003: 521-523.

Copyright International Journal of Pharmaceutical Compounding Nov/Dec 2004
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