Making drug-embedded matrix tablets through the direct compression of a blend of drug, retardant material, and additives is one of the simplest formulation approaches. The inclusion of polymeric materials in a matrix system is a common method of modulating drug release (1). Drug-release retarding polymers are the key performers in matrix systems. Various polymers have been investigated as drug-retarding agents, each presenting a different approach to the matrix system. Based on the features of the retarding polymer, matrix systems are usually classified into three main groups: hydrophilic, hydrophobic, and plastic. Hydrophilic polymers are most suitable for retarding drug release, and interest is growing in using these polymers in sustained drug delivery (2–4).

In India, natural gums and mucilage are well known for their medicinal use. Natural gums and mucilage are preferred to semisynthetic and synthetic excipients because of their lack of toxicity, low cost, availability, soothing action, and nonirritant nature (5–8). Many natural materials are studied for use in sustained-release tablets. These materials include: guar gum (9), ispaghula husk (10), olibanum and its resins (11), cross-linked high amylose starch (12), Ulmus fulva (slippery elm mucilage) (13), pectin (14), Peumus boldus dry plant extract (15), galactomannon from Mimosa scabrella (16, 17), Gleditsia triacanthos Linn (honey locust gum) (18), Sesbania gum (19), mucilage from the pods of Hibiscus esculenta (20), Tamarind seed gums (21), and gum copal and dammar (22).

Hibiscus rosa-sinensis Linn has not been explored as a pharmaceutical excipient. Hibiscus rosa-sinensis Linn of the Malvaceae family is also known as the shoe-flower plant, China rose, and Chinese hibiscus. The plant is available in India in large quantities, and the leaves contain mucilage (23, 24). The leaves are used in traditional medicines as emollients and aperients to treat burning sensations, skin disease, and constipation (25). The plant contains cyclopropanoids, methyl sterculate, methyl-2-hydroxysterculate, 2-hydroxysterculate malvate, and β-rosasterol. Mucilage of Hibiscus rosa-sinensis contains L-rhamnose, D-galactose, D-galactouronic acid, and D-glucuronic acid (26). The leaves contain carotene (7.34 mg/100 g of fresh material) and are used as cattle feed (27). The leaves also contain moisture, protein, fat, carbohydrate, fibers, calcium, and phosphorus (28).

Diclofenac sodium is a potent nonsteroidal anti-inflammatory drug. Diclofenac sodium rapidly dissolves in intestinal fluid, reaches its maximum blood concentration (Cmax) within 30 min, and is metabolized mainly by hepatic hydroxylation and subsequent conjugation (29). In healthy human volunteers, the mean plasma clearance of diclofenac sodium was 16.0 L/h, and the mean elimination half-life of the terminal phase was 1.2–1.8 h (30). To reduce gastrointestinal irritation, a common problem with all nonsteroidal anti-inflammatory agents, effective enteric-coated dosage forms have been developed. Food delays the absorption of the drug, which causes a nonreproducible pharmacokinetic profile, and the drug has no immediate therapeutic effect (31).

Drug release from hydrophilic matrices is a complex interaction between dissolution, diffusion, and the erosion mechanism. In this study, the drug-release mechanism was evaluated for diclofenac sodium tablets prepared with highly hydrophilic mucilage from the leaves of Hibiscus rosasinensis Linn. A 3² full factorial design was carried out to evaluate the effect of certain variables such as the amount of mucilage and diluent. Further studies were performed using water uptake, the mass loss of pure mucilage, and the matrix tablet containing the drug and mucilage. A stability study for an optimized batch was performed for three months.