Stability of Solutions of 2,3-diphenylcyclopropenone in Various Solvents. a Novel Formula - Diphenylcyclopropenone in Isopropanol May Be Useful in Topical Therapy of Patients with Alopecia Areata.

The aim of this study was to evaluate the chemical stability of diphenylcyclopropenone (DCP) in var- ious solvents. DCP is being used in topical therapy in patients with alopecia areata (AA). The solvents for DCP used so far were acetone, ethanol and propylene glycol. DCP is supposed to be an immune-modulating thera- peutic agent, however the studies on it's pharmacokinetics including chemical stability are lacking. In a pres- ent study, DCP was dissolved in acetone (A), ethanol (E), propylene glycol (PG) and isopropanol (I). Solutions at two concentrations: 0.1 and 3.0% were prepared in each of these solvents. Then, the solutions were divided into two parts - one'of which was stored at room temperature and the other in a refrigerator (at about 4⁰C) with- out the access of light. In determined time intervals the solutions were analyzed and the content of DCP and it's main decomposition product DPA was assessed. The stability of solutions of DCP with all the solvents kept in a refrigerator (at about 4⁰C) without light was maintained, the decomposition rate after 60 days was negligible. In contrary, DCP solutions kept at room temperature after 60 days decomposed visibly and in different rates according to a solvent (PG > I > E > A). The most surprising finding was that DCP solutions in acetone, which was supposed to be a good solvent for the purpose of AA treatment, decomposed completely (100%) after just 45 days at room temperature. The most stable solutions at room temperature turned out to be the ones in propy- lene glycol and isopropanol. Results suggest: 1. the preferable storage condition for all DCP solutions is at a temperature of about 4⁰C without the access of light; 2. there is a limited benefit from'using acetone as a DCP solvent; 3. the novel solvent for DCP - isopropanol, showed good stability in both temperatures and has favor- able cosmetic qualities. In conclusion, authors suggest to make further investigations on DCP in isopropanol solutions in clinical studies regarding treatment of AA.