📙 This book entitled - Formulation variables of Transdermal Drug Delivery Systems: Gels Contains detailed formulation Study of drug release behaviour and rheological properties of gels. inclusion of ingredients such as hydroxy propyl cellulose,carboxy methyl ccellulose, sodium lauryl sulphate , tween etc plays a important role in drug release and formulation behaviour. The importance of ingredients can be understand only after the precise delivery of drug at a determined or predetermined rate.