Liraglutide

Liraglutide is an acylated synthetic glucagon-like peptide-1 (GLP-1) analog produced by recombinant DNA technology. It shares approximately 97% sequence homology with native human GLP-1, with two key structural modifications: an arginine substitution for lysine at position 34, and a C-16 fatty acid (palmitic acid) attached via a γ-glutamic acid spacer at lysine 26. The fatty acid chain enables reversible binding to serum albumin in subcutaneous tissue and the bloodstream, slowing absorption, protecting the molecule from enzymatic degradation, and reducing renal clearance.

Mechanism of Action

Liraglutide is an agonist at the GLP-1 receptor, a G-protein-coupled receptor linked to adenylate cyclase. Receptor activation increases intracellular cyclic AMP, producing the following effects:

• Glucose-dependent insulin secretion: stimulates pancreatic beta cells to release insulin only when blood glucose is elevated, minimizing hypoglycemia risk.
• Glucagon suppression: inhibits glucagon release in a glucose-dependent manner; does not impair the counter-regulatory glucagon response to hypoglycemia.
• Slowed gastric emptying: reduces the rate of postprandial glucose appearance.
• Appetite regulation: acts on hypothalamic centers to reduce hunger, increase satiety, and lower preference for high-fat foods, leading to decreased caloric intake.

Pharmacokinetics

• Bioavailability: approximately 55% after subcutaneous injection.
• Tmax: ~11.7 hours.
• Volume of distribution: ~13 L.
• Protein binding: >98% (predominantly albumin).
• Metabolism: slowly degraded by dipeptidyl peptidase-4 (DPP-4) and neutral endopeptidase (neprilysin) into smaller polypeptides; a portion is fully metabolized to CO₂ and water.
• Half-life: ~13 hours, supporting once-daily dosing.
• Steady state: achieved after ~3 days of daily dosing.
• Excretion: 6% in urine and 5% in feces (predominantly as metabolites; intact liraglutide is not excreted).

In the SCALE clinical trial program for chronic weight management:

• Average weight loss: approximately 8% of body weight (vs 2.6% with placebo).
• Responders: 63% of patients lost ≥5%, and 33% lost ≥10% of body weight.
• Cardiovascular risk: improvements in waist circumference, blood pressure, and lipid parameters.
• Glycemic control: HbA1c reduction of approximately 1.3% in patients with type 2 diabetes.
• Reduced progression from prediabetes to type 2 diabetes.

Chronic weight management (Saxenda, 3 mg once daily) — as an adjunct to a reduced-calorie diet and increased physical activity in:

• Adults with obesity (BMI ≥30 kg/m²), or overweight (BMI ≥27 kg/m²) with at least one weight-related comorbidity (hypertension, type 2 diabetes, dyslipidemia, obstructive sleep apnea).
• Pediatric patients ≥12 years old who weigh ≥60 kg and have an initial BMI corresponding to obesity based on international cut-offs.

Type 2 diabetes mellitus (Victoza, lower-dose formulations up to 1.8 mg daily) — as adjunct to diet and exercise to improve glycemic control in patients ≥10 years old with type 2 diabetes; as monotherapy or in combination with other antidiabetic medications.

Cardiovascular risk reduction — to reduce the risk of major adverse cardiovascular events (cardiovascular death, non-fatal myocardial infarction, non-fatal stroke) in adults with type 2 diabetes and established cardiovascular disease.

Combination therapy (Xultophy) — liraglutide is also available combined with insulin degludec as an adjunct to diet and exercise in adults with type 2 diabetes mellitus.

Treatment Evaluation

Discontinue liraglutide for weight management if a patient has not lost at least 4% of baseline body weight after 16 weeks at the 3 mg/day dose; clinically meaningful weight loss is unlikely with continued treatment.

• Hypersensitivity to liraglutide or any of the excipients.
• Personal or family history of medullary thyroid carcinoma (MTC).
• Multiple endocrine neoplasia syndrome type 2 (MEN 2).
• Pregnancy and breastfeeding.
• Inflammatory bowel disease and diabetic gastroparesis (for the 3 mg weight-management formulation).

Use with caution / limited data: patients ≥75 years (limited experience), severe renal or hepatic impairment, end-stage renal disease (not studied), NYHA class III–IV heart failure, patients weighing >160 kg (not studied).

Very Common (>10%): nausea, diarrhea, constipation, vomiting, headache, dyspepsia, upper abdominal pain.

Common (1–10%): hypoglycemia (in diabetic patients on concomitant therapy), insomnia, dizziness, dysgeusia, dry mouth, gastritis, gastroesophageal reflux, abdominal distension, flatulence, eructation, fatigue, injection site reactions, cholelithiasis, increased lipase and amylase.

Uncommon (<1%): dehydration, acute pancreatitis, delayed gastric emptying, allergic reactions, increased heart rate.

Gastrointestinal effects are typically mild to moderate and decrease over time, particularly during dose escalation.

• Oral medications: delayed gastric emptying may affect absorption; take oral medications requiring rapid GI absorption 1 hour before liraglutide if needed.
• Insulin and insulin secretagogues: increased hypoglycemia risk; consider dose reduction.
• Warfarin: monitor INR when initiating or discontinuing.
• Oral contraceptives: no clinically significant interaction.

Do not mix liraglutide with other injectable medications.

Liraglutide is administered once daily by subcutaneous injection at any time of day, with or without food. Inject in the abdomen, thigh, or upper arm; rotate sites and use a new needle each time. Do not inject intravenously or intramuscularly.

Dose Escalation (Weight Management — 3 mg target)

• Week 1: 0.6 mg once daily.
• Week 2: 1.2 mg once daily.
• Week 3: 1.8 mg once daily.
• Week 4: 2.4 mg once daily.
• Week 5 onwards: 3.0 mg once daily (maintenance).

If a dose increase is not tolerated for 2 consecutive weeks, consider discontinuing treatment.

Missed Dose

• If the next scheduled dose is more than 12 hours away: administer as soon as possible.
• If less than 12 hours away: skip the missed dose.
• If more than 3 days have elapsed since the last dose: reinitiate at 0.6 mg to reduce gastrointestinal symptoms.

Pancreatitis Warning

Discontinue if pancreatitis is suspected (persistent severe abdominal pain, pain radiating to the back, with or without vomiting). Do not restart if pancreatitis is confirmed.

Thyroid C-Cell Tumors

In animal studies, liraglutide caused thyroid C-cell tumors. Counsel patients on symptoms (neck mass, hoarseness, dysphagia, dyspnea).

Gallbladder Disease

Substantial weight loss increases the risk of cholelithiasis. Inform patients about symptoms of gallstones.

Hypoglycemia

Risk increases when combined with insulin or sulfonylureas. Educate patients on recognition and treatment of hypoglycemia.

Heart Rate

May increase resting heart rate by 2–3 beats per minute. Monitor; discontinue if sustained tachycardia occurs.

Renal Function

Gastrointestinal side effects may cause dehydration and acute renal failure. Ensure adequate hydration.

Pregnancy and Lactation

Discontinue if pregnancy occurs. Use effective contraception during treatment. Excretion in breast milk is not established; not recommended during breastfeeding.

Effect on Driving

May cause dizziness or fatigue. Use caution when driving or operating machinery.

Before first use: store in a refrigerator at 2–8°C, away from the freezer element, in the original package. Do not freeze. Protect from light.

After first use: store at or below 30°C or refrigerated (2–8°C). Use within 30 days. Keep the cap on when not in use.

Dispose of used pens after 30 days even if some solution remains.

30 months when stored properly. Do not use after the expiry date.

Prescription required.