Phentermine is a controlled drug in Cayman. Semaglutide is not

In the Cayman Islands, two weight-loss medicines that a patient may ask about in the same consultation are regulated by two very different laws. Phentermine, an older appetite suppressant, is a controlled drug under the Misuse of Drugs Act (2026 Revision), the consolidated text published with Legislation Gazette No. 8 of 10 February 2026¹. Semaglutide and tirzepatide, the GLP-1-based injectables that now dominate obesity care, are not on that list. They fall under the Pharmacy Law, 1979, an eight-page statute that still governs medicine imports because its replacement, the Pharmacy Act, 2024, is still listed as not in force²¹⁴. For prescribers, the difference shapes record keeping, inspection, refills and penalties.

Which weight-loss drugs the Misuse of Drugs Act controls

Schedule 1 of the Act sets out the controlled drugs in three parts¹. Part 3, the list that holds the benzodiazepines, also names a group of older anorectic agents: benzphetamine, chlorphentermine, diethylpropion, fenproporex, mazindol, mefenorex, phendimetrazine and phentermine, along with cathine and cathinone¹. Any salt, stereoisomer or preparation containing them is controlled too (paragraphs 2 to 4 of Part 3)¹. No GLP-1 receptor agonist, and no other peptide hormone, appears anywhere in Schedule 1¹.

Section 3 makes it an offence, "without lawful excuse or without being authorised in that behalf", to import, store, supply, dispense, administer or possess a controlled drug, and it lists "issues a prescription for" among the regulated acts¹. The general penalty in section 16(1) is a fine of three thousand dollars and three years' imprisonment with hard labour on summary conviction, rising to ten thousand dollars and ten years for a third or subsequent conviction¹. Physicians prescribe phentermine lawfully because they are authorised persons; the Act matters because it attaches a separate regime of rules and inspection to every such prescription.

The Chief Medical Officer's rule-making power

Section 14 is the key provision for clinicians: "The C.M.O. may make rules for inspection, keeping of inventories, and general control and distribution of controlled drugs in the hands of persons authorised under this Act to be in possession of the same"¹. Anyone authorised must, at the request of the CMO or a constable, "account for the distribution of all such drugs as have passed through that person's hands"¹. Under section 13, Cabinet may make regulations on the import, export, transport and storage of controlled drugs and attach penalties for breaking the section 14 rules¹.

That power has been used. In January 2024 Cayman News Service reported the then Chief Medical Officer, Dr. Nick Gent, saying that "rules had been introduced for doctors to only prescribe addictive medicines like opioids on a monthly basis" and that "this did not apply to all prescription drugs, just those that pose a risk of addiction"³. In May 2024 he said the scale of prescribing of addictive medicines "concerns me an awful lot"⁴. Dr. Hilary Wolf, a physician with two decades of global health experience, was appointed Chief Medical Officer in October 2025⁵, and in April 2026 the Ministry named Dr. Mark Paramlall as the first deputy CMO, a post that carries statutory duties under the Mental Health, Public Health, Health Practice and Pharmacy Acts⁶. Which Schedule 1 drugs a given CMO rule covers is set out in the rule itself, not in the Act.

Where semaglutide and tirzepatide sit: the Pharmacy Law, 1979

The 1979 law controls "pharmaceutical products having potential danger to health if misapplied"². It defines a restricted pharmaceutical as one prescribed as such by regulation "which may not be dispensed or administered except under prescription and all drugs scheduled in the Misuse of Drugs Law, 1973"². Section 11 says that anyone who is not the Chief Medical Officer, a medical practitioner, the Chief Agricultural Officer or a pharmacist and who "imports, dispenses or otherwise deals in restricted pharmaceuticals is guilty of an offence"; section 12 bars a pharmacist from dispensing one without a prescription; section 15 requires records of every restricted pharmaceutical acquired and dispensed². The penalty in section 20 is a fine not exceeding $1,000 or up to six months in prison, or both². Section 21 states that nothing in the Pharmacy Law derogates from the Misuse of Drugs Law².

So phentermine is caught twice: as a restricted pharmaceutical under the 1979 definition, which takes in every drug scheduled in the Misuse of Drugs Law, and as a controlled drug under the Misuse of Drugs Act itself¹². A GLP-1 injectable is governed by the Pharmacy Law alone, with a penalty ceiling set in 1979².

What the evidence says about the two drug classes

Phentermine's reputation still carries the fenfluramine-phentermine episode: in 1997 investigators described 24 women with unusual valvular morphology and regurgitation after fenfluramine-phentermine, eight with newly documented pulmonary hypertension and five needing cardiac surgery⁷. That report concerned the combination, not phentermine alone⁷. Modern data on phentermine itself are more reassuring. In an electronic health record cohort of 13,972 adults, patients using phentermine continuously for more than 12 months lost 7.4% more weight at 24 months than short-term users, with no significant difference in a composite of cardiovascular disease or death (41 events, 0.3%)⁹. In 269 patients, including 117 treated long term, structured interviews found no phentermine abuse or psychological dependence and no amphetamine-like withdrawal on stopping¹⁰.

Efficacy is where the classes separate. In the CONQUER trial of 2,487 patients, phentermine plus topiramate reduced weight by 7.8% and 9.8% at 56 weeks at the two doses, against 1.2% with placebo⁸. In STEP 1, semaglutide 2.4 mg produced a mean change of -14.9% at 68 weeks versus -2.4% with placebo¹¹. In SURMOUNT-1, tirzepatide reached -20.9% at the 15 mg dose at 72 weeks versus -3.1% with placebo¹². In December 2025 the World Health Organization issued its first guideline on GLP-1 medicines for obesity, with conditional recommendations covering liraglutide, semaglutide and tirzepatide, and warned that demand "has fueled the spread of falsified and substandard products"¹³.

• Phentermine: controlled drug (Schedule 1, Part 3), subject to section 14 CMO rules and section 16 penalties¹.
• Semaglutide, tirzepatide: governed by the Pharmacy Law, 1979; for restricted pharmaceuticals, import and dealing are limited to the CMO, medical practitioners, the Chief Agricultural Officer and pharmacists (section 11)².
• Restricted pharmaceuticals: a pharmacist may dispense them only on prescription, and every dispenser keeps records of stock acquired and dispensed (sections 12 and 15)².