Transdermal administration of bromocriptine.

Abstract

Bromocriptine (BRC) has been mainly used for the inhibition of lactation, treatment of menstrual disorders, Parkinson disease, breast tumours, infertility and brain tumours as a dopamine agonist in clinics. But current BRC formulations have some side effects and bioavailability problems because of hepatic first pass effect. Transdermal application could be an alternative route to overcome all these problem and penetration properties of BRC has not been studied yet. Therefore, it was aimed to investigate the effectiveness of transdermal formulation of BRC which is applicable to the skin. For this purpose, a number of BRC gel formulations (Carbopol-934 (C-934), chitosan (CH) and Gantrez-SP215 (G-SP215) were developed and the effectiveness and bioavailability of the formulations were compared in rabbits. Commercial BRC tablets (Parlodel) were also given to rabbits orally and plasma levels were compared. The effects of two different penetration enhancers, sodium taurocholate (ST) and ethoxydiglycol-Transcutol) (TR) on the BRC penetration were also investigated. The skin samples from the dorsal part of the rabbit were removed after CH gel application and investigated under electron microscope to understand the effects of the gel on the penetration and the possible penetration mechanisms through skin were also discussed. In conclusion, CH gel formulation was found to be the best formulation and comparable blood BRC concentrations were obtained when applied to the rabbit skin. Higher blood levels were obtained with the use of CH. The main penetration process was found to be through transcellular route but some other mechanisms were also found to be incorporated, after microscopic investigation. CH gel was found to be a useful carrier for BRC administration through dermal route and the penetration enhancing effect and the mechanism of CH gel were first established in this study. It was concluded that transdermal delivery of BRC may be a very promising alternative route to the oral route for the treatment.