The Side Effects of Drugs Annuals form a series of volumes in which the adverse effects of drugs and adverse reactions to them are surveyed. The series supplements the contents of Meyler's Side Effects of Drugs: the International Encyclopedia of Adverse Drug Reactions and Interactions. This review of the 2011 publications on drugs that act on the cerebral and peripheral circulations covers buflomedil, cilostazol, pentoxifylline, diosmin, ergot alkaloids, the triptans, and inhibitors of phosphodiesterase type V. The risk of buflomedil toxicity in patients with impaired renal function using current French dosage guidelines has been estimated at about 6%. Leukopenia has been attributed to pentoxifylline. Ergot alkaloids have been shown to have direct cytotoxic effects in two primary human cell lines. Myocardial infarction with coronary vasospasm on angiography has been associated with a triptan. The co-administration of sildenafil and hydrochlorothiazide may have been responsible for a case of hypotension triggering acute spinal cord infarction. Increased choroidal thickness has been attributed to sildenafil. Tadalafil might have triggered visual scotomata as a manifestation of Leber's hereditary optic neuropathy.