Background and Importance Difficulties in drug supply makes pharmacists find alternative ways to provide functional therapy. API from available pharmaceutical forms can be used as a substance for compounding medicine. Drug effectiveness needs be considered as well as compatibility with excipients and primary packing material. Variable temperature, humidity, light can stimulate changes in all pharmaceutical forms, especially in solutions. Primary packing material should provide protection of dosage forms and compatibility with the medicine.

Aim and Objectives Aim of this study was to examine compounding clindamycin topical solution made from available clindamycin hydrochloride oral dosage forms. Effect of excipients and filtration process was evaluated. Drug stability determine not only effectiveness of drug, but also its safety. Patients may store solution in places that may be inadequate. The study compared glass and plastic bottles for storing the solution.

Material and Methods Method for assay determination was HPLC reversed phase with UV detector. Assay and peaks of related substances and impurities were evaluated. Solution was divided in glass and plastic bottles and stored at light exposure, elevated, decreased and room temperature. Sampling was according to free judgment.

Results Sample solution meets the assay requirements with assay 92% acceptance criteria is 90–110%. No significant API degradation and related substances were noticed. Samples stored in plastic bottles showed assay increase up to 26% compared to samples in glass bottles where reported growth is up to 5%.

Conclusion and Relevance Clindamycin hydrochloride solution for topical use can be made from oral pharmaceutical forms. Compounding process did not have relevant impact to assay of API. Molecule is stable at least 112 days under mentioned conditions. However, assay increase was noticed in plastic HDPE bottles due to vehiculum evaporation which is more expressed in samples conditioned in elevated temperatures. Container closure system should enable adequate closing between cap and bottle which is a key parameter to be considered.

References and/or Acknowledgements 1. James R. Falconer, Kathryn J. Steadman. Extemporaneously compounded medicines. Australian Prescriber, 2017;Vol.40(1).

2. Hitesh Chavda. In-Use stability guidelines and challenges. Drug Development and Industrial Pharmacy, 2021;Vol.47(9).

3. European Medicines Agency, Committee for proprietary medicinal products (CPMP), In-use stability testing of human medicinal products – Scientific guideline.

Conflict of Interest No conflict of interest.