Despite recent advances in the treatment of patients with acute ischaemic stroke or intracerebral haemorrhage (ICH), about half of the patients still have a poor outcome. The available treatments with the largest benefit, intravenous thrombolysis and endovascular treatment, are available for a relatively small proportion of patients. Hence, there is a need for additional treatment available for a larger group of stroke patients, preferably applicable very soon after symptom onset according to the ‘time is brain’ principle.

A potential therapeutic target in patients with acute stroke is the improvement of collateral perfusion and reduction of blood pressure. Recent studies have suggested that transdermal administration of glyceryl trinitrate (GTN; nitroglycerin), in the first hours after symptom onset, increases the chance of a favourable outcome after stroke, possibly through an increase in intracranial collateral blood flow and a reduction in blood pressure. The Multicentre Randomised trial of Acute Stroke treatment in the Ambulance with a nitroglycerin Patch (MR ASAP) aims to assess the effect of transdermal GTN, started within three hours of stroke onset in the prehospital setting, on functional outcome at 90 days in patients with acute ischaemic stroke or intracerebral haemorrhage.

The primary objective of MR ASAP is to assess the effect of transdermal GTN, started within 3 hours of symptom onset in the prehospital setting, on functional outcome at 90 days in patients with acute ischaemic stroke or intracerebral haemorrhage.
Secondary objectives are to assess whether the effects of transdermal GTN on functional outcome are consistent across specific subgroups of patients, i.e., those with 1. ischaemic stroke; 2. ischaemic stroke treated with endovascular techniques; or 3. intracerebral haemorrhage; and to assess the effect of GTN on collaterals, size of the ischemic core and salvageable brain tissue on admission to the hospital.