Semaglutide

GLP-1 Agonist·Endocrinology - Insulins & Injectables

Type 2 Diabetes, Obesity (BMI > 30, or > 27 with comorbidities), reduction of major cardiovascular events

Authority requiredPBSGLP-1Ozempic (T2DM), Wegovy (Obesity), Rybelsus (Oral)Pre-filled multi-dose pens f…+2

Max Dose

2.4 mg/week

Half-life

1 WEEK

Weight Loss

MASSIVE

Pancreatitis

RISK

Rapid Summary

Overview

The most potent GLP-1 agonist available. Provides unparalleled weight loss and cardiovascular mortality benefits. Dosed once weekly.

Maximum Dose

Max 1 mg/week (Ozempic for Diabetes) or 2.4 mg/week (Wegovy for Weight Loss).

Clinical Focus

Drastically slows gastric emptying. Anaesthetists require the drug to be withheld prior to surgery to prevent fatal pulmonary aspiration under anaesthesia.

Bottom Line

Semaglutide is the most potent GLP-1 agonist with landmark cardiovascular and weight loss outcomes, but causes significant GI side effects and is contraindicated in personal/family history of medullary thyroid carcinoma.

Formulation & Access

Brand Names

Ozempic (T2DM), Wegovy (Obesity), Rybelsus (Oral)

Parenteral

Pre-filled multi-dose pens for SC injection.

Prescribing & PBS

Authority Required (PBS) for Ozempic. Private script for Wegovy.

Indications & Use

Primary

PBSTGA

Type 2 Diabetes, Obesity (BMI > 30, or > 27 with comorbidities), reduction of major cardiovascular events.

Clinical Place

The blockbuster drug of modern endocrinology. Revolutionizing the treatment of obesity and diabesity.

Quick reference

Class & Role

GLP-1 Agonist — The most potent GLP-1 agonist available.

Route / Formulation

Pre-filled multi-dose pens for SC injection. (Ozempic (T2DM), Wegovy (Obesity), Rybelsus (Oral))

Usual Dose & Max

SC 0.25 mg once weekly for 4 weeks. Increase to 0.5 mg weekly. Max 1 mg/week.

Key Indication Doses

Type 2 Diabetes (Ozempic): SC 0.25 mg once weekly for 4 weeks. Increase to 0.5 mg weekly. Max 1 mg/week. Weight Loss (Wegovy): SC Titrated slowly over 5 months from 0.25 mg up to 2.4 mg once weekly. Type 2 Diabetes (Oral Rybelsus): PO 3 mg OD for 1 month, then 7 mg OD. Max 14 mg/day. (MUST take with 120mL water on an empty stomach, wait 30 mins before eating).

Best Uses

Avoid / Cautions

Personal/family history of Medullary Thyroid Carcinoma or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2). History of pancreatitis. Pregnancy Category D. Must be ceased 2 months before planned conception.

Key Risks

Gastrointestinal: Nausea (up to 45%), vomiting, diarrhea, severe constipation. CRITICAL — Acute pancreatitis, gastroparesis, bowel obstruction/ileus. Endocrine: Medullary thyroid carcinoma (seen in rodents, theoretical risk in humans). Renal: AKI secondary to severe dehydration from vomiting.

Key Interactions

Delays the absorption of rapidly acting oral medications due to gastric stasis.

Monitoring

Counsel patients to eat tiny portions. If they eat a normal-sized heavy meal, the delayed stomach emptying will cause them to vomit it back up. Routine HbA1c, Weight, and U&E.

Clinical Pearl

Rybelsus is a pharmacological miracle. GLP-1 is a peptide that is instantly destroyed by stomach acid. Rybelsus contains an absorption enhancer (SNAC) that locally buffers stomach acid and forces the peptide across the gastric wall. However, if the patient takes it with more than half a glass of water, or eats within 30 minutes, the SNAC is washed away and absorption is ZERO.

Access

Authority requiredOzempic (T2DM), Wegovy (Obesity), Rybelsus (Oral)

Brand: Ozempic (T2DM), Wegovy (Obesity), Rybelsus (Oral)
PBS status: Authority required