A study into the long-term prescription of quinine for muscle cramps has found it may lead to increased mortality in patients.
The paper, published in JAMA by researchers from University College London and Paris-Est Créteil Val-de-Marne University, found that exposure to a median level of 203mg/d was associated with 4.2 deaths per 100 person-years, compared to 3.2 deaths per 100 person-years for unexposed individuals.
The study looked at 175,195 individuals from a dataset of 12 million anonymised individuals from 562 general practices in the UK.
The exposed group was limited to adults who received new quinine salt prescriptions for idiopathic muscular cramps or restless leg syndrome for at least one year, at an average dose of 100mg/d or more.
The authors concluded: ‘The benefits of quinine in reducing cramps should be balanced against the risks.’
Neither NICE nor the Medicines and Healthcare products Regulatory Agency (MHRA) recommend off-label prescription of quinine for treatment of muscle cramps. But although NICE analysis cites the poor benefit-to-risk ratio of the treatment, it does say trial treatment may be considered if cramps are frequent and impacting quality of life.
If the treatment is given, NICE recommends 200-300mg of quinine be prescribed daily for 4-6 weeks. If this is beneficial, the treatment may be continued with review every 3-6 months.
Consultant senior lecturer in primary health care at the University of Bristol, Dr Rupert Payne, said ‘The results raise some concern that long-term quinine use may be associated with increased mortality.
‘The fact that this effect appears to be dose-dependent strengthens this conclusion. However, this is an observational study, so there’s always the possibility that some other unmeasured confounding factor may explain the increased risk.’