Dizziness dipyridamole

Adverse reactions at therapeutic doses are usually minimal and transient. With long-term use, initial side effects usually disappear. The following reactions were reported in 2 heart valve replacement trials comparing dipyridamole and warfarin therapy to either warfarin alone or warfarin and placebo dizziness, abdominal distress, headache, and rash. 

A 74-year-old woman had a 3-year history of mild dysarthria, dizziness, and gait ataxia, accompanied by two transient ischemic attacks with involuntary ballistic movements of her left arm lasting several seconds each, and another transient ischemic attack with a right homonymous hemianopia lasting 30 minutes. About 45 minutes after her first-ever oral administration of dipyridamole plus aspirin she developed a transient cerebellar deficit that reproduced features of previous vertebrobasilar ischemic events, as well as severe headache, flushing, and diarrhea. 

Adverse effects with dipyridamole thallium testing are minimal, the main adverse effects being chest pain (with or without ischemic changes on the ECG), headache, dizziness, and nausea. Adverse effects are related to the increased adenosine activity and can be ameliorated by xanthine compounds because they are direct competitive antagonists of adenosine. Caffeine products must be avoided for about 24 hours prior to the test. Adenosine is associated with a higher incidence of adverse effects (80% versus 50%), but these are very transient, and some studies have shown that patients prefer it over dipyridamole. Both agents are relatively contraindicated in patients with a history of bronchospasm. 

A 79-year-old woman taking a combination of low-dose aspirin and extended-release dipyridamole (Aggrenax) became profoundly bradycardic (36 bpm), dizzy and almost fainted 2 minutes after the start of an adenosine infusion for radionuclide myocardial imaging. Adenosine was stopped, and she recovered within 2 minutes. The last dose oiAggrenox had been taken 12 hours previously. However, note that bradycardia is a known adverse effect of adenosine. ... 

A 67-year-old woman with hypertension, who was taking metoprolol 50 mg bd, underwent dipyridamole stress testing, and during the infusion of dipyridamole developed nausea, dizziness, and sudden loss of consciousness. 

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