Dipyridamole

INTRODUCTION

Indications

PO: Prevention of thromboembolism in patients with prosthetic heart valves (with warfarin). Maintains patency after surgical grafting procedures, including coronary artery bypass (with aspirin). IV: As an alternative to exercise in myocardial perfusion scintigraphy (cardiac stress testing with radiotracer imaging).

Action

PO: Decreases platelet aggregation by inhibiting the enzyme phosphodiesterase. IV: Produces coronary vasodilation by inhibiting adenosine uptake. Therapeutic Effects: PO: Inhibition of platelet aggregation and subsequent thromboembolic events. IV: In diagnostic thallium imaging, dipyridamole dilates normal coronary arteries, reducing flow to vessels that are narrowed and causing abnormal thallium distribution.

Adverse Reactions/Side Effects

CNS: dizziness, headache, syncope IV only: transient cerebral ischemia, weakness. Resp: IV only: bronchospasm. CV: IV only: MI, hypotension, arrhythmias, flushing. GI: nausea, diarrhea, GI upset, vomiting. Derm: rash.

PHYSICAL THERAPY IMPLICATIONS

Examination and Evaluation

• Be alert for signs of transient cerebral ischemia, including sudden weakness/numbness on one side of the body, slurred speech, loss of vision, dizziness, and loss of balance and coordination. Report these signs to the physician immediately.

• Watch for symptoms of bronchospasm (wheezing, coughing, tightness in chest), especially after IV administration. Perform pulmonary function tests to quantify suspected changes in ventilation and respiration (See Appendices I, J, K).

• Assess heart rate, ECG, and heart sounds, especially during exercise (See Appendices G, H). Report any rhythm disturbances or symptoms of increased arrhythmias, including palpitations, chest discomfort, shortness of breath, fainting, and fatigue/weakness.

• Assess blood pressure periodically and compare to normal values (See Appendix F). Report low blood pressure (BP) (hypotension), especially if patient experiences dizziness or syncope.

• Assess dizziness that might affect gait, balance, and other functional activities (See Appendix C). Report balance problems and functional limitations to the physician, and caution the patient and family/caregivers to guard against falls and trauma.

Interventions

• Because of the risk of arrhythmias and abnormal BP responses, use caution during aerobic exercise and endurance conditioning. Assess exercise tolerance frequently (BP, heart rate, fatigue levels), and terminate exercise immediately if any untoward responses occur (See Appendix L).

Patient/Client-Related Instruction

• Remind patients to take medication as directed to reduce the risk of thromboembolism or graft occlusion even if they are asymptomatic.

• Counsel patients about additional interventions to help reduce the risk of heart disease, including regular exercise, weight loss, sodium restriction, stress reduction, moderation of alcohol consumption, and smoking cessation.

Pharmacokinetics

Absorption: Moderately absorbed (30–60%) after oral administration.

Distribution: Widely distributed. ...