A top insurer has announced restrictions on where its clients can purchase certain high-cost drugs — including the weight loss GLP-1 pharmaceuticals Ozempic, Mounjaro and Wegovy.

The medications, developed to treat diabetes, have soared in popularity on the island for treatment of obesity, putting pressure on the healthcare system because of their high price tag.

Allshores Ltd posted an online listing of its deal with Phoenix Stores, which the insurer claimed would curtail rising costs and protect coverage for its clients.

The approved list covers a suite of other drugs ranging from the ADHD medication Adderall to specialised pharmaceuticals for conditions such as cystic fibrosis and psoriasis.

Allshores clients will be directed to Phoenix from March 1 for medications listed at allshores.com/phoenix.

A company spokeswoman said high-cost prescription drugs “including GLP-1 treatments, biologics and oncology therapies have become one of the fastest-growing drivers of spending”.

Despite representing about 3 per cent of prescriptions, they were said to account for more than 30 per cent of expenses.

Allshores said the move had been undertaken in keeping with requests from its employer clients, and was “increasingly common internationally” for cost containment.

The selection of Phoenix pharmacies followed a request for proposal process.

Effective April 1, new prescriptions for the listed medications filled at other pharmacies will be subject to coverage under separate health plans.

The spokeswoman said pharmacy benefits would not be reduced.

“Benefit schedules have not changed and coverage levels remain the same. In some cases, coverage for certain high-cost medications has improved.

“For most plans, eligible medications continue to be covered at 100 per cent with no co-pay or deductible when dispensed through the designated pharmacy partner.”

Allshores said clients were being informed, with “targeted outreach for those with chronic conditions who would be directly impacted”.

Physicians and pharmacies were also told, with relevant prescriptions directed to Phoenix pharmacies.

The move was not said to affect regular prescriptions, with Allshores members free to fill non-high-cost medications at pharmacies of their choice, in line with their existing coverage.

Allshores, which came out of the merger of BF&M and Argus last year, completed its rebrand last December.