Preformulation studies of finasteride to design matrix systems for topical delivery.

•Preformulation of finasteride was performed using a simplex centroid mixture design.•Drug interaction with polymers and cyclodextrin were identified by thermal analysis.•Hydroxypropyl cellulose facilitated cyclodextrin-drug inclusion complex formation.•Chemical stability of the different mixtures was preserved after thermal treatment.•Interaction with excipients suggest s a stabilization of the original drug crystalline phase.