Abstract
Photostability profiles of minoxidil solutions exposed to fluorescent light, under the influence of several parameters like concentration, pH, buffer species, photostabilizers, container type, solvent system, and skin penetration enhancers were studied. The assay of minoxidil was done spectrophotometrically at 230 nm and 290 nm, using double beam UV-visible spectrophotometer. The results show that photodegradation of minoxidil solutions follows first order rate. Furthermore, minoxidil solution (4.5 µg/ml) was found to be more stable in phosphate buffer as compared to acetate buffer. Amber glass offered equivalent photoprotection as aluminum foil-covered glass. Minoxidil was found to be most stable in a solvent system of water or 25% v/v PEG300 and least stable in 25% v/v propylene glycol. Of the penetration enhancers studied dimethyl sulfoxide (DMSO) caused the least photodecomposition of minoxidil. The order of photoprotection of the five potential photostabilizers were as follows: sodium thiosulfate > EDTA > sodium benzoate ≈ thiourea > sodium metabisulfite. Varying the concentration of sodium thiosulfate did not affect the minoxidil photostability. The study also indicates that minoxidil solution (4.5 µg/ml) is most photostable in pH 8 phosphate buffer. An increase in ionic strength had a photostabilizing effect until an optimum strength of 0.17, then further increase caused the rate of photodegradation to remain unchanged.
- Received January 11, 1995.
- Accepted July 31, 1995.
- Copyright © Parenteral Drug Association. All rights reserved.
PDA members receive access to all articles published in the current year and previous volume year. Institutional subscribers received access to all content. Log in below to receive access to this article if you are either of these.
If you are neither or you are a PDA member trying to access an article outside of your membership license, then you must purchase access to this article (below). If you do not have a username or password for JPST, you will be required to create an account prior to purchasing.
Full issue PDFs are for PDA members only.
Note to pda.org users
The PDA and PDA bookstore websites (www.pda.org and www.pda.org/bookstore) are separate websites from the PDA JPST website. When you first join PDA, your initial UserID and Password are sent to HighWirePress to create your PDA JPST account. Subsequent UserrID and Password changes required at the PDA websites will not pass on to PDA JPST and vice versa. If you forget your PDA JPST UserID and/or Password, you can request help to retrieve UserID and reset Password below.