Among the various routes of administration oral route is the most convenient, easy and preferred one. However, orally administered drugs are either prone to hepatic first-pass metabolism or metabolism in gastrointestinal (GI) tract or both. These are the main reasons for which some classes of drugs like peptides and proteins cannot be administered orally. Delivery of drugs through various mucosal surfaces (nasal, rectal, vaginal, ocular and oral mucosa) may form the potential alternative solution for delivery of such classes of drugs. These mucoadhesive drug delivery systems improve the bioavailability of the drugs by bypassing the first pass effects and avoiding the presystemic elimination of the drug within the GI tract[1]. Out of the various sites available for mucoadhesive drug delivery, buccal mucosa is the most suited one for local as well as systemic delivery of drugs. It's anatomical and physiological features like presence of smooth muscles with high vascular perfusion, avoidance of hepatic first pass metabolism and hence can potentially improve bioavailability are the unique features which make it as an ideal route for mucoadhesive drug delivery. Moreover, these dosage forms are economic and patient-friendly.
The drug dissolution (release) and permeation through the mucosa are governed by microenvironment of the mucosa. The microenvironment of the mucosa can be adjusted or modified with the help of well-designed mucoadhesive drug delivery systems[2]. These systems are designed and formulated with the help of mucoadhesive polymers which are generally of high molecular weight and of high viscosity grades with greater flexibility and optimum chain length. Various mucoadhesive polymers have also been investigated for buccal drug delivery[3,4,5]. Among the various mucoadhesive drug delivery systems, buccal films are better than oral gels and buccal tablets due to relatively longer residence time, more flexibility to cover the buccal mucosa and better comfort.
Enalapril maleate is an angiotensin converting enzyme (ACE) inhibitor, used mainly in the treatment of hypertension and angina pectoris. It has low bioavailability (40-60%) due to hepatic first pass metabolism[6]. Hence to improve its therapeutic efficacy and bioavailability the drug may be administered by buccal route through buccal films. Buccal delivery of enalapril maleate may circumvent hepatic first pass metabolism and improve bioavailability. Hence the present work deals with the formulation and characterization of mucoadhesive buccal film of enalapril maleate using mucoadhesive polymer sodium carboxymethylcellulose (SCMC), hydroxylpropylmethylcellulose (HPMC), hydroxyethylcellulose (HEC) and polyvinyl pyrrolidone K-90 (PVP K-90).