Answer
Nimodipine belongs to a group of drugs called calcium-channel blockers. In very simple terms, these are drugs that 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.
The previous use of nimodipine in ME/CFS was partly based on the fact that neuroimaging (using blood flow SPECT scans) 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. And, as you say, there is more recent research evidence suggesting problems with cerebral blood flow in ME/CFS. Even so, the use of nimodipine in ME/CFS has always been unproven (as there haven't been any proper clinical trials) and highly speculative.
Some private doctors have been willing to prescribe nimodipine in the past 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 sideeffects. These can include hypotension (lowering of blood pressure), heart rate disturbances, headaches, sweating, nausea and gastric upsets. So this is a drug that 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 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.
Having said all that, I think there is a case for looking at this drug again under the NIHR research initiative to fund repurposing drug trials for acute post infection syndromes.
