Objectives
The aim was to evaluate ointments for local treatment of anal fissures. Nitroglycerin (NTG) was complexed with β‐cyclodextrin (β‐CD) to provide prolonged NTG release, with the intention of decreasing systemic drug absorption and thus reducing side effects.
Methods
Gels, creams and anhydrous water‐emulsifying (AWE) ointment with NTG‐CD were compared with preparations containing uncomplexed NTG (diluted with crospovidone, NTG‐cP). The in‐vitro NTG release and ex‐vivo skin absorption were studied.
Key findings
The prolonged‐release ointment with the NTG‐CD complex was formulated using AWE base or w/o cream (20% water); release of NTG from a hydrogel was very fast with both the complexed and uncomplexed forms. From the AWE ointment base, 16.4% or 4.5% of the total NTG dose was released after 6 h when NTG‐cP or NTG‐CD was incorporated, respectively. With the complexed form, NTG absorption to the skin after a 5‐h application was 18.1 or 11.1 μg/g from AWE ointment or cream, respectively; absorption of the uncomplexed NTG was higher: 52.3 or 21.9 μg/g from AWE ointment and cream, respectively.
Conclusions
Complexation with β‐CD results in prolonged release of NTG from AWE ointment and w/o cream, which was confirmed by the ex‐vivo skin absorption results.