Systemic pharmacomodulation of transient lower esophageal sphincter relaxations

Abstract

Transient lower esophageal sphincter relaxations (TLESRs) are the major mechanism of reflux in patients with gastroesophageal reflux disease. They are therefore attractive targets for pharmacotherapy. During the past 5 years, there has been a burgeoning interest in the neural pathways that control these events and in the pharmacologic receptors involved in these pathways. Several agents have been shown to reduce the rate of TLESRs, including cholecystokinin-A antagonists, anticholinergic agents, nitric oxide synthase inhibitors, morphine, somatostatin, serotonin type 3-receptor antagonists, and gamma-aminobutyric acid-B (GABA(B)) agonists. Their predominant site of action appears to be on either the afferent pathways and/or the central integrative mechanisms within the dorsal vagal complex in the brainstem. Most of the agents tested are unsuitable for clinical use either because of side effects or because of the lack of an orally effective formulation. The most promising agents identified to date are the GABA(B) agonists. Baclofen, the prototype GABA(B) agonist, inhibits the rate of TLESRs by more than 50%. Control of TLESRs is a major new approach to the treatment of reflux disease. It is likely to be applicable to the majority of patients, particularly those without macroscopic mucosal lesions or only mild erosive disease. Further development of more effective agents will depend both on a better understanding of the neural pathways and receptors involved in the control of TLESRs, as well as on investigation of other novel agents. At present, inhibition of TLESRs is at the threshold of transition from concept to practical use. Whether it makes the final leap into the mainstream of therapy will depend on the development of new, novel, and well-targeted pharmacologic agents.