MELTING AND DISSOLUTION OF DRUG DELIVERY COATINGS

Melting and dissolution of drug delivery coatings

Melting and dissolution of drug delivery coatings

Introduction

Enteric coatings are pH sensitive and have traditionally been used to prevent the release of a drug in the stomach. Enteropolymers (enteric-coated polymers) protect a dosage form from the acidic environment of the stomach and allow drug delivery to the small or large intestine (site specific drug delivery), depending on their dissolution pH and the thickness of the coating applied. Although enteric-coated formulations are used mainly in connection with site-specific delivery, as utilized in time-controlled drug administration, when a lag time is needed (Robinson and Lee 1987). Enteric coating can be considered as a pulsatile drug delivery system because the lag time is essential for the drugs that undergo degradation in gastric acidic medium, cause gastric irritation, some drugs which induce nausea or vomiting, all such drug requires drug release after lag time. Pulsed fashion can be achieved by the enteric coating of delivery system. It can also be used for chronotherapeutic time controlled systems when a lag-time is needed for drug release (Wilding et al. 1994).

Melting and dissolution of drug delivery coatings

Such system offers many advantages over conventional oral drug delivery systems like patient compliance, reduced dosage, and reduced dosage frequency, avoidance of side effects, avoidance of peak and valley fluctuation, nearly constant drug level at the target site. The lag time of the pulsatile release tablets could be controlled by the coating level of polymer applied which is turn related to the permeation and mechanical properties of the polymer coating (Gazzaniga et al. 1995).

Chronotropic® system is one of pulsatile drug delivery system consists of a core containing drug reservoir coated by a hydrophilic polymer hydroxylpropylmethylcellulose (HPMC) (Giordano et al. 1994). An additional enteric-coated film is given outside this layer to overcome intra-subject variability in gastric emptying rates. The lag time and the onset of action are controlled by the thickness and the viscosity grade of HPMC (Sangalli et al. 1999). In the treatment of nocturnal asthma a Salbutamol formulation containing a barrier coating which is dissolved in intestinal pH level above about 6, has successfully been used (Bogin and Ballard 1992). Furthermore Sinha et al. designed a pulsatile system by using fast release enteric-coated tablets for targeted drug delivery of celecoxib for prophylaxis of colorectal cancer.

Objectives

The present study explores the comparative utility of the enteropolymers such as acrycoat L-100, ...