Semaglutide

Semaglutide is a GLP-1 receptor agonist — a 31-amino-acid peptide analogue of glucagon-like peptide-1 (GLP-1) with 94% sequence homology to the endogenous hormone. It was engineered with an 18-carbon fatty acid chain attached to its lysine residue, enabling strong albumin binding and extending its half-life to approximately 7 days — far beyond the 2-minute half-life of native GLP-1. Approved by the FDA under the brand names Ozempic (type 2 diabetes), Wegovy (chronic weight management), and Rybelsus (oral tablet), it is one of the most clinically validated peptides in modern medicine, with landmark trials demonstrating 15–17% mean body weight reduction over 68 weeks.

Semaglutide activates the GLP-1 receptor (GLP-1R), which is expressed in the pancreas, brain, gastrointestinal tract, heart, and liver. In the pancreas, GLP-1R activation stimulates glucose-dependent insulin secretion (it only releases insulin when blood glucose is elevated — a key safety advantage over older antidiabetics), suppresses glucagon, and slows gastric emptying, leading to prolonged satiety after meals. In the hypothalamus, semaglutide activates appetite-regulating circuits (particularly POMC neurons in the arcuate nucleus), reducing caloric intake by 20–30% through both delayed gastric emptying and central appetite suppression. Cardiovascular benefits documented in the SUSTAIN and STEP trials include reduction in major adverse cardiac events (MACE) — attributed to anti-inflammatory effects on arterial endothelium, reduced blood pressure, and direct cardiac GLP-1R signaling.

Semaglutide has one of the most robust clinical trial records of any peptide in medical history. The SUSTAIN trial program (10 trials, 5,000+ patients with T2DM) demonstrated HbA1c reduction of 1.0–1.8% and weight loss of 4–6 kg. The STEP trial program (8 trials, 5,000+ obese/overweight subjects) demonstrated 15–17% mean body weight reduction over 68 weeks — the most effective non-surgical weight loss intervention ever documented. The SELECT trial (17,000+ patients with CVD, no diabetes) demonstrated a 20% reduction in major adverse cardiovascular events (MACE). FDA approved under Ozempic (2017), Wegovy (2021), and Rybelsus oral (2019). The SELECT trial's MACE data represents a landmark in peptide cardiovascular medicine.

Weight Management Research Protocol: Titrate from 0.25 mg/week to maintenance dose of 1–2.4 mg/week over 16–20 weeks. Maintain at target dose for 24–52 additional weeks with dietary monitoring. Diabetes Management: 0.5–1 mg once weekly as GLP-1 monotherapy. Compound Protocol (research grade): 0.25 mg subcutaneous first week, increase 0.25 mg every week until target dose. Always combine with slow dose escalation plan and dietary guidance.

Gastrointestinal effects are the primary dose-limiting side effects, occurring in 40–70% of patients: nausea (most common), vomiting, diarrhea, constipation, and abdominal pain. These are most pronounced during dose escalation and typically improve significantly after 4–8 weeks at a stable dose. A small percentage of patients develop pancreatitis — risk is elevated in those with a personal or family history. Thyroid C-cell hyperplasia and medullary thyroid carcinoma have been observed in rodent models — semaglutide is contraindicated in patients with a personal or family history of medullary thyroid carcinoma or MEN2. Hypoglycemia is rare unless combined with insulin or sulfonylureas. Rapid weight loss can precipitate gallstone formation. Injection site reactions occur in a small minority.

Unopened Wegovy/Ozempic pens: store at 2–8°C (refrigerator). Once in use, pens can be stored at room temperature (below 30°C) for up to 56 days. Compounded/lyophilized semaglutide: store at 2–8°C protected from light, reconstitute with bacteriostatic water, use within 28 days. Semaglutide is sensitive to heat — do not leave in a car or direct sunlight. Do not freeze. The fatty acid chain makes semaglutide more fragile to reconstitution — gentle swirling (never vigorous shaking) is required.