Nimodipine belongs to a group of drugs called calcium-channel blockers.
In very simple terms these drugs relax the smooth muscle in the walls of blood vessels and cause them to dilate.
So they are mainly used to lower blood pressure, treat angina, and improve the circulation in people who have Raynaud's phenomenon (cold hands and feet).
Nimodipine is slightly different to other drugs in the group in that its main site of action is on blood vessels in the brain (the cerebral arteries).
So its use is mainly confined to the prevention of vascular spasm following a rare type of stroke known as an aneurysmal subarachnoid haemorrhage. Nimodipine has also been reported to be of benefit in improving cognitive function in dementia and reducing pain associated with cancer.
The proposed use of nimodipine in ME/CFS is partly based on the fact that neuroimaging (ie SPECT scan) studies have identified abnormalities in cerebral blood flow, and there is some evidence to suggest that at a cellular level ME/CFS may be what is known as a calcium channelopathy – see section 5:5 in ‘ME/CFS/PVFS – An Exploration of the Key Clinical Issues' (MEA publication).
However, the use of nimodipine in ME/CFS remains unproven (as far as clinical trials are concerned) and highly speculative.
Some private doctors are willing to prescribe nimodipine but the small amount of feedback I have received over the years is very mixed. As with most speculative and experimental forms of treatment some people claim benefit; others show no effect; and a few report side-effects.
Side-effects can include hypotension (lowering of blood pressure); heart rate disturbances; headaches; sweating, nausea and gastric upsets. So this drug has to be used with great care.
In the absence of any results from clinical trials, and the fact that this is not a licensed prescribable treatment for ME/CFS, most GPs would be reluctant to prescribe nimodipine – as a doctor could be legally liable if anything went wrong as a result.
Dr Charles Shepherd
Hon Medical Adviser, The ME Association