Cholesterol-lowering drugs given to millions of people cause muscle pain, stiffness, cramps and weakness in about a quarter of patients taking them because they interfere with the way cells produce energy, scientists have discovered.

Statins are highly effective at reducing blood levels of cholesterol, a major risk factor for heart disease, but can also have unwanted side effects.

In some cases the adverse reactions are so disruptive that people stop taking the drugs.

The new research has uncovered the reason for common statin side effects – interference with mitochondria, the rod-shaped energy-generating power houses in cells.

Frans Russel, from Radboud University Medical Centre in the Netherlands, who co-led the study, said: “This research leads to several opportunities to synthesise new classes of cholesterol-lowering drugs without the unwanted muscle effects, as well as the development of new avenues to counteract these effects, both of which we are currently investigating.”

The new research shows how statins change in the body from an acid to a “lactone” form that has no therapeutic effect but can disrupt the ability of mitochondria to generate energy.

Evidence of this was seen both in mouse studies and tests of muscle tissue samples from patients suffering from statin side effects.

In the patients, production of adenosine triphosphate (ATP), a chemical that transports energy within cells, was lower than normal.

Russel added: “Further independent studies are needed on the effects of the different statins on mitochondrial function... Inter-individual differences in the enzymatic conversion of the acid into the lactone (statin) form could be an explanation for the differences between patients in susceptibility for statin-induced muscle pain.”

The research is reported in the journal Cell Metabolism.