The Medicines and Healthcare products Regulatory Agency (MHRA) has warned healthcare professionals to be vigilant when prescribing Amgen's bone drug Prolia following reports of thigh breaks in patients taking the drug in a clinical study assessing its long-term use.

Two patients with post-menopausal osteoporosis receiving long-term treatment (more than 2.5 years) with Prolia (denosumab) 60mg were reported to have suffered an atypical femoral fracture, similar in nature to those observed with long-term biphosphonate therapy, it said.

This equates to a frequency of at least one but fewer than 10 cases per 10,000 patients (according to PJ Online), prompting the watchdog to issue a safety update on the drug.

The Agency is advising doctors to stress to patients the importance of reporting any unusual thigh, hip, or groin pain, and to evaluate any such symptoms for an incomplete femoral fractures.

Discontinuation of treatment should be considered if an atypical femur fracture is suspected while the patient is being evaluated, and an individual assessment of the benefits and risks should also be performed, it said.

The National Institute for Health and Clinical Excellence published guidance recommending the use of Prolia on the National Health Service as an option for preventing primary and secondary osteoporotic fractures in postmenopausal women back in 2010, for patients unable to take the oral bisphosphonates alendronate and either Procter & Gamble’s Actonel (risedronate) or etidronat.

Its endorsement of the drug was based on data from the FREEDOM study, which showed that the 36-month incidence of new radiographically-diagnosed vertebral fractures was found to be just 2.3% in women taking Prolia compared to 7.2% in those given a placebo.

Denosumab is a first-in-class monoclonal antibody that reduces osteoclast activity and thereby bone breakdown. It is also on the market under the trade name Xgeva (120mg), for patients with bone metastases from solid tumours, and the MHRA warned that a risk of atypical femoral fractures linked with this product cannot be ruled out.

Man sentenced for drug mailing

Meanwhile, the regulator separately announced that a Portuguese national has been sentenced to 44 months in prison after £1.6 million worth of unlicensed, prescription-only-medicines and Class C drugs was seized at his property.

An investigation by the MHRA uncovered an illicit drug mailing operation distributing "vast amounts" of fake medicines and unlicensed erectile dysfunction therapies, as well as powerful Class C drugs such as the opiate Tramadol, tranquiliser drug Diazepam and testosterone.

Nimo Ahmed, MHRA Acting Head of Enforcement, has urged people to only take prescription-only medicines after seeing their GP. 

"They are best equipped to consider your medical history, the risk and benefits of drugs and any possible interactions with other medicines you’re taking,” he stressed.