<p>Increased rate of verteporfm uptake by the vascular endothelium with calcium channel blockers, polymyxin B or radiation therapy. Increased photosensitivity with photosensitizing agents (e.g. tetracyclines, sulfonamides, phenothiazines, sulfonylurea hypoglycaemic agents, thiazide diuretics and griseofulvin). Decreased verteporfm efficacy with compounds that quench active oxygen species or scavenge radicals e.g. dimethyl sulfoxide, betacarotene, ethanol, formate and mannitol. Decreased verteporfm efficacy with drugs that decrease clotting, vasoconstriction or platelet aggregation e.g. thromboxane A2 inhibitors. Anaesthetics may cause haemodynamic effects.</p>