2021 · Novo Nordisk
Semaglutide (Wegovy, Ozempic)
Drug class. GLP-1 receptor agonist, weekly injection
Wegovy 2.4 mg weekly was approved for chronic weight management in 2021. Ozempic, the same drug, was first approved in 2017 for type 2 diabetes. The Wegovy dose starts at 0.25 mg and rises every 4 weeks to 2.4 mg at week 17.[1][2][3]
Trial results. In STEP 1 (1,961 adults, 68 weeks), weight fell 14.9% against 2.4% on placebo; 86.4% lost at least 5% and 50.5% at least 15%. In SELECT (17,604 adults with heart disease), heart attack, stroke or cardiovascular death fell from 8.0% to 6.5%.
Trade-offs. Nausea 44%, diarrhea 30%, vomiting 24% and constipation 24% in Wegovy trials. 6.8% stopped for side effects against 3.2% on placebo. Boxed warning for thyroid C-cell tumors.
2023 · Eli Lilly
Tirzepatide (Zepbound, Mounjaro)
Drug class. GIP and GLP-1 receptor agonist, weekly injection
Zepbound was approved for chronic weight management on November 8, 2023. Mounjaro, the same drug, was first approved in 2022 for type 2 diabetes. The dose starts at 2.5 mg and rises in 2.5 mg steps after at least 4 weeks to 5, 10 or 15 mg.[1][2][3]
Trial results. In SURMOUNT-1 (2,539 adults, 72 weeks), weight fell 15.0%, 19.5% and 20.9% on 5, 10 and 15 mg against 3.1% on placebo. In SURMOUNT-5 (751 adults), tirzepatide lowered weight 20.2% against 13.7% for semaglutide.
Trade-offs. Side effects are mostly gastrointestinal and occur mostly during dose escalation. 4.3% to 7.1% stopped for adverse events against 2.6% on placebo. Boxed warning for thyroid C-cell tumors.
2014 · Novo Nordisk
Liraglutide (Saxenda)
Drug class. GLP-1 receptor agonist, daily injection
Saxenda 3 mg is injected once a day. Liraglutide shares 97% of its amino acid sequence with human GLP-1 and has a 13 hour half-life, against 1.5 to 2 minutes for native GLP-1.[1][2][3]
Trial results. In SCALE (3,731 adults, 56 weeks), weight fell 8.4 kg against 2.8 kg on placebo; 63.2% lost at least 5% against 27.1%. The label says to stop if weight loss is under 4% at 16 weeks.
Trade-offs. Nausea in 39% against 14% on placebo. Daily rather than weekly injections.
1959 · Teva (Adipex-P)
Phentermine (Adipex-P)
Drug class. Sympathomimetic amine, oral
Phentermine was first approved in 1959. The label limits it to short-term use, a few weeks, as an adjunct to diet and exercise. It is a Schedule IV controlled substance.[1][2][3]
Trial results. Short-term appetite suppression. It is also the phentermine component of Qsymia.
Trade-offs. Rare cases of primary pulmonary hypertension and serious valvular heart disease are on the label. In 1997, valve disease was reported in 24 women who took fenfluramine with phentermine.
2012 · Vivus
Phentermine-topiramate (Qsymia)
Drug class. Sympathomimetic plus anticonvulsant, oral capsule
Qsymia combines phentermine with extended-release topiramate, taken once a day. It is Schedule IV. Because topiramate raises the risk of oral clefts in pregnancy, only certified pharmacies may dispense it under a REMS program.[1][2]
Trial results. In CONQUER (2,487 adults, 56 weeks), weight fell 9.8% on 15/92 mg and 7.8% on 7.5/46 mg against 1.2% on placebo. The label says to stop if weight loss is under 5% after 12 weeks on the top dose.
Trade-offs. On the top dose: dry mouth 21%, tingling 21%, constipation 17%, insomnia 10%, dizziness 10% and altered taste 10%. Depression-related events 7% against 4% on placebo.
2014 · Orexigen Therapeutics
Naltrexone-bupropion (Contrave)
Drug class. Opioid antagonist plus antidepressant, oral tablet
Contrave combines naltrexone, an opioid antagonist, with bupropion, a weak inhibitor of dopamine and norepinephrine reuptake. It acts on the hypothalamus and the brain's reward system.[1][2]
Trial results. In COR-I (1,742 adults, 56 weeks), weight fell 6.1% against 1.3% on placebo; 48% lost at least 5% against 16%. The label says to stop if weight loss is under 5% after 12 weeks on the full dose.
Trade-offs. Boxed warning for suicidal thoughts and neuropsychiatric reactions. Nausea in 29.8% against 5.3% on placebo. Blood pressure, heart rate and seizure risk are on the label.
2022-2025 · Compounding pharmacies and outsourcing facilities
Compounded semaglutide and tirzepatide
Drug class. Unapproved copies, often in multi-dose vials
Compounders may copy an approved drug while it is on the FDA shortage list. Tirzepatide and semaglutide injections were in shortage from 2022. FDA declared the tirzepatide shortage resolved on December 19, 2024 and the semaglutide shortage on February 21, 2025. Grace periods ended for pharmacies after court rulings on March 5 and April 24, 2025, and for outsourcing facilities on March 19 and May 22, 2025.[1][2][3]
Trial results. FDA: compounded drugs should only be used when a patient's needs cannot be met by an FDA-approved drug. As of April 2026, neither drug is on the 503B bulks list or the shortage list.
Trade-offs. Not FDA approved or reviewed for safety, effectiveness or quality. As of May 31, 2026, FDA had 990 adverse event reports for compounded semaglutide and more than 730 for compounded tirzepatide. FDA warns of dosing errors, salt forms (semaglutide sodium and acetate), fraudulent labels and warm shipments. In December 2025 FDA seized counterfeit Ozempic 1 mg found in the US supply chain.