gastroretentive system

Normally a tablet is swept out of the stomach within hours, like a leaf carried off by a stream. A gastroretentive system is designed to resist that current and linger in the stomach so it can keep releasing drug from there.

Staying in the stomach is useful in several situations: for drugs that are mainly absorbed in the upper small intestine (so they should be delivered there steadily), for drugs that act locally on the stomach lining, and for drugs that are unstable or poorly soluble lower in the gut. Strategies to achieve retention include floating systems that are lighter than gastric fluid, high-density systems that sink below the outlet, swelling or expanding systems too large to pass through the pylorus, and mucoadhesive systems that cling to the stomach lining.

Reliable gastric retention is genuinely difficult. The stomach periodically contracts strongly to clear undigested material (the migrating motor complex), and retention depends heavily on whether the patient has eaten, on meal size and type, on posture, and on individual variation. As a result many gastroretentive products perform inconsistently, and the approach works best when combined with food and clear dosing instructions.