Indications
Semaglutide is designed for use in conjunction with a calorically reduced diet and increased physical activity. It is indicated for improving glycemic control in adults with type 2 diabetes mellitus, with the understanding that it is not a first-line treatment for diabetes that is uncontrollable with diet and exercise alone. Importantly, semaglutide is not recommended for individuals with type 1 diabetes or for the treatment of diabetic ketoacidosis, and its efficacy in patients with pancreatitis has not been investigated. Additionally, semaglutide is approved for chronic weight management in adults who are obese or overweight and have at least one associated weight-related condition, such as hypertension, type 2 diabetes, or hyperlipidemia. In pediatric patients aged 12 and above, it is used for chronic weight management if their body mass index (BMI) is at or above the 95th percentile for their age and sex. Moreover, semaglutide is indicated to reduce the risk of major adverse cardiovascular events-including cardiovascular death, non-fatal myocardial infarction, and non-fatal stroke-in adults with established cardiovascular disease and either obesity or overweight.
Pharmacodynamics
Semaglutide is effective in lowering HbA1c, systolic blood pressure, and body weight. Within the first 12 weeks of treatment, it achieves a reduction in fasting and postprandial glucose by promoting insulin secretion and inhibiting glucagon release, thereby improving blood sugar control. Semaglutide also decreases fasting triglycerides and very low-density lipoprotein (VLDL) cholesterol, positively impacting cardiovascular health. Animal studies have shown that semaglutide can lead to medullary thyroid cell carcinoma in rodents; however, the relevance of these findings to humans is undetermined. The FDA advises against the use of semaglutide in individuals with a personal or family history of medullary thyroid carcinoma. There are additional risks of pancreatitis and dehydration associated with semaglutide. Patients should maintain adequate hydration and seek immediate medical attention if experiencing abdominal pain that radiates to the back. Due to its effect on delaying gastric emptying, it is crucial to monitor the effectiveness and potential side effects of other orally administered drugs concurrently used with semaglutide.
Absorption
In clinical trials, semaglutide exhibited a peak plasma concentration (Cmax) of 10.9 nmol/L and an area under the curve (AUC) of 3123.4 nmol h/L, with a time to peak concentration (Tmax) of approximately 56 hours, achieved within 1 to 3 days post-administration. The drug has an absolute bioavailability of 89%. When administered as an oral tablet, semaglutide reaches a steady-state concentration within 4 to 5 weeks, with average steady-state levels ranging from 16 nmol/L to 30 nmol/L with doses of 0.5 mg to 1 mg.
Metabolism
Semaglutide undergoes metabolic transformation primarily through cleavage at the peptide backbone followed by β-oxidation of its fatty acid chain. Unlike the naturally occurring glucagon-like peptide-1 (GLP-1), which is rapidly degraded by dipeptidyl peptidase-4 (DPP-4) and other enzymes, semaglutide is chemically modified to resist enzymatic breakdown by gastrointestinal DPP-4. It is predominantly metabolized slowly, with approximately 83% of the administered dose detected as unchanged drug in the plasma. Neural endopeptidase (NEP) also contributes to its metabolism. Six different metabolites have been identified in human plasma, with the major metabolite, referred to as P3, accounting for about 7.7% of the ingested dose.
Mechanism of Action
Semaglutide, a GLP-1 receptor agonist, closely resembles human GLP-1, sharing 94% structural similarity. It enhances glycemic control through multiple mechanisms, including the stimulation of insulin secretion, delaying gastric emptying, and decreasing postprandial glucagon release. This regulation of glucose homeostasis relies on hormones like insulin and amylin, which are produced by the pancreatic beta cells. By selectively binding to the GLP-1 receptor, semaglutide activates pancreatic islet cells to increase insulin synthesis and decrease glucagon secretion, leading to a reduction in blood glucose levels in a glucose-dependent manner. Beyond glycemic control, semaglutide is associated with cardiovascular benefits and weight loss. In the context of hypercholesterolemia, it appears to mitigate the progression of atherosclerosis by reducing gut permeability and inflammation. Additionally, semaglutide contributes to weight loss by diminishing appetite and food cravings.
