Dexlansoprazole

Generic Name: Dexlansoprazole

Brand Names: Dexilant

Drug Type: Small Molecule

Chemical Formula: C_₁₆H_₁₄F_₃N_₃O_₂S

CAS Number: 138530-94-6

Unique Ingredient Identifier: UYE4T5I70X

Background: Dexlansoprazole is a new generation proton pump inhibitor (PPI) used for the management of symptoms associated with gastroesophageal reflux disease (GERD) and erosive esophagitis. Dexlansoprazole is the R-enantiomer of Lansoprazole, which is composed of a racemic mixture of the R- and S-enantiomers. Compared to the older generation of PPIs (which includes Pantoprazole, Omeprazole, and Lansoprazole) , dexlansoprazole MR has a unique pharmacokinetic profile due to its delayed-release and dual-delivery release system. The active ingredient is released in two phases at different pH values and at different time points, resulting in two peak concentrations in the blood; 25% of the dose is released at pH 5.5 in the proximal duodenum, while the remaining 75% is released at pH 6.75 in the distal small intestine . As a result, dexlansoprazole has a peak concentration within 1-2 hours after dosing and another within 4-5 hours . Dexlansoprazole's unique pharmacokinetics addresses limitations of the older generation PPIs including short plasma half-life, break-through symptoms, and need for meal-associated dosing . These characteristics make dexlansoprazole a good option for people who struggle with adherence and strict dosage timing before meals.

Dexlansoprazole exerts its stomach acid-suppressing effects in the same way as other drugs in the PPI family by inhibiting the final step in gastric acid production. Dexlansoprazole targets the (H+, K+)-ATPase enzyme, which is involved in the secretion of hydrochloric acid through the exchange of H+ ions from the cytoplasm for K+ ions. Normally functioning (H+, K+)-ATPase stimulates hydrochloric acid secretion into the gastric lumen thereby increasing stomach acidity and lowering pH. Once absorbed into circulation, dexlansoprazole covalently binds to the sulfhydryl groups of cysteines found on the (H+, K+)-ATPase enzyme at the secretory surface of gastric parietal cells, which leads to inhibition of both basal and stimulated gastric acid secretion. Despite dexlansoprazole's unique pharmacokinetic profile, efficacy in management of GERD symptoms is considered similar to other medications within the PPI class including Omeprazole, Esomeprazole, Lansoprazole, Pantoprazole, and Rabeprazole.

Due to their good safety profile and as several PPIs are available over the counter without a prescription, their current use in North America is widespread. Long term use of PPIs such as dexlansoprazole have been associated with possible adverse effects, however, including increased susceptibility to bacterial infections (including gastrointestinal C. difficile), reduced absorption of micronutrients including iron and B12, and an increased risk of developing hypomagnesemia and hypocalcemia which may contribute to osteoporosis and bone fractures later in life . PPIs such as dexlansoprazole have also been shown to inhibit the activity of dimethylarginine dimethylaminohydrolase (DDAH), an enzyme necessary for cardiovascular health. DDAH inhibition causes a consequent accumulation of the nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA), which is thought to cause the association of PPIs with increased risk of cardiovascular events in patients with unstable coronary syndromes .

Dexlansoprazole doses should be slowly lowered, or tapered, before discontinuing as rapid discontinuation of PPIs such as dexlansoprazole may cause a rebound effect and a short term increase in hypersecretion .