1 Section of Neurology, Psychiatry and Sensory Sciences, Department of Clinical Medicine, Faculty of Health and Medical Sciences, Københavns Universitet2 unknown3 Department of Clinical Medicine, Department of Clinical Medicine, Faculty of Health and Medical Sciences, Københavns Universitet4 Neuro- og Sansefag5 Department of Clinical Medicine, Department of Clinical Medicine, Faculty of Health and Medical Sciences, Københavns Universitet
InvestigationSodium nitroprusside (SNP) is a powerful vasodilatory agent that, similarly to glyceryl trinitrate (GTN), releases nitric oxide (NO) but in contrast does not pass the blood-brain barrier. Nevertheless, it has already been used in animal models without any knowledge of its headache-inducing potential. We hypothesized that SNP would induce headache and vasodilation of cephalic and radial but not cerebral arteries.MethodsFive healthy volunteers received intravenous infusions of SNP in a non-randomized dose-titration (1-5 µg/kg/min) study. We recorded headache intensity (verbal rating scale from 0 to 10), velocity in the middle cerebral artery (V(MCA)), and diameters of the superficial temporal artery (STA) and radial artery (RA).ResultsAll participants reported a dose-related headache (median peak = 2.5, range 0-3). SNP dilated the STA and RA, caused a marked increase of heart rate and a decrease of mean arterial pressure (MAP) and partial pressure of end-tidal carbon dioxide (P(et)CO(2)). We found that SNP decreased the velocity of the V(MCA), but this was canceled by a decrease of cerebral blood flow (CBF) due to hypocapnia.ConclusionThe present study shows that SNP is a headache-inducing agent with close similarities to headaches induced by GTN and probably without effect on intracerebral arteries.