(3R)-3-Amino-1-[3-(trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazin-7-yl]-4-(2,4,5- trifluorophenyl)butan-1-one

Mechanism of action

Sitagliptin prolongs the activity of proteins that increase the release of insulin after blood sugar rises, such as after a meal. Sitagliptin is a selective inhibitor of the enzyme dipeptidyl peptidase-4 (DPP-4), which metabolizes the naturally occurring incretin hormones glucagon-like peptide-1(GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) resulting in enhanced glucose-dependent insulin secretion from the pancreas and decreased hepatic glucose production. Since GLP-1 enhances insulin secretion in the presence of raised blood glucose levels, inhibiting DPP-IV activity will increase and prolong the action of GLP-1 by reducing its rate of inactivation in plasma. Sitagliptin reduces hemoglobin A1c (HbA1c), fasting and postprandial glucose by glucose-dependent stimulation of insulin secretion and inhibition of glucagon secretion. GLP-1 has other widespread effects including delaying gastric emptying, significantly reducing glucagons levels and possible central effects on the appetite.

Pharmacokinetics

Bioavailability of sitagliptin is approximately 87%. Halflife is between 8-14 hours. It is 38% bound to plasma proteins. It undergoes limited metabolism via CYP3A4 and CYP2C8. Elimination is mainly through urine.

Indications

Sitagliptin is approved by the FDA as an adjunct to diet and exercise to improve glycaemic control in patients with T2DM, either as a monotherapy, or in combination with metformin or a peroxisome proliferatoractivated receptor-γ agonist (for example, thiazolidinediones) when the single agent does not provide adequate glycaemic control.

Side effects

In clinical trials, sitagliptin demonstrated an overall incidence of side effects comparable to placebo. The most common side effects in studies were upper respiratory tract infection, stuffy or running nose, sore throat, headache and diarrhea. The incidence of hypoglycemia with sitagliptin monotherapy was not significantly different than placebo. Pooled data from 2 monotherapy and 2 combination trials show that the incidence of hypoglycemia was 1.2% and 0.9% for sitagliptin 100mg and placebo respectively.

Drug interactions

Sitagliptin plasma concentrations may be increased modestly (approximately 68%), with cyclosporine which is not expected to be clinically important. Digoxin plasma levels may be increased slightly (approximately 18%), no dosage adjustment is recommended. Although sitagliptin is not as likely to cause hypoglycemia as some other oral diabetes medications, be careful while prescribing any other drug that can potentially lower blood sugar, such as: probenecid, nonsteroidal anti-inflammatory drugs (NSAIDs), aspirin or other salicylates, sulfa drugs, a monoamine oxidase inhibitor (MAOI) or beta-blockers.

Definition

ChEBI: Sitagliptin is a triazolopyrazine that exhibits hypoglycemic activity. It has a role as a serine proteinase inhibitor, a hypoglycemic agent, an EC 3.4.14.5 (dipeptidyl-peptidase IV) inhibitor, an environmental contaminant and a xenobiotic. It is a triazolopyrazine and a trifluorobenzene.

Brand name

Januvia

Metabolism

Sitagliptin undergoes minimal metabolism, mainly by the cytochrome P450 isoenzyme CYP3A4, and to a lesser extent by CYP2C8. Renal excretion of sitagliptin involves active tubular secretion; it is a substrate for organic anion transporter-3 and P-glycoprotein.