Pharmacologic: phosphodiesterase type 5 inhibitors
Increases cyclic guanosine monophosphate (cGMP) levels by inhibiting phosphodiesterase type 5 (PDE5), an enzyme responsible for the breakdown of cGMP. cGMP produces smooth muscle relaxation of the corpus cavernosum, which in turn promotes increased blood flow and subsequent erection. Therapeutic Effects: Enhanced blood flow to the corpus cavernosum and erection sufficient to allow sexual intercourse. Requires sexual stimulation.
Adverse Reactions/Side Effects
CNS: headache, amnesia, dizziness. EENT: HEARING LOSS, VISION LOSS, rhinitis, sinusitis. CV: arrhythmias. GI: dyspepsia, nausea. GU: priapism. Derm: flushing. Misc: flu syndrome.
PHYSICAL THERAPY IMPLICATIONS
Examination and Evaluation
Be alert for sudden loss of vision or hearing, and seek emergency care for any changes in vision or hearing.
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 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.
Because of the risk of arrhythmias, use caution during aerobic exercise and other forms of therapeutic exercise. Assess exercise tolerance frequently (blood pressure, heart rate, fatigue levels), and terminate exercise immediately if any untoward responses occur (See Appendix L).
Instruct patient to notify health care professional promptly if erection lasts longer than 4 hr or if he experiences a sudden decrease or loss of vision or hearing.
Instruct patient and family/caregivers to report other bothersome side effects such as severe or prolonged headache, memory loss, nasal congestion/inflammation, flu-like symptoms, skin problems (flushing), or GI reactions (nausea, indigestion).
Absorption: 15% absorbed following oral administration; absorption is rapid.
Distribution: Extensive tissue distribution; penetrates semen.
Metabolism and Excretion: Mostly metabolized by the liver (mainly CYP3A4 enzyme system, minor metabolism by CYP2C). M1 metabolite has antierectile dysfunction activity. Parent drug and metabolites are mostly excreted in feces. 2–6% renally eliminated.
Contraindicated in: Hypersensitivity; Concurrent use of nitrates or nitric oxide donors; Unstable angina, recent history of stroke, life-threatening arrhythmias, CHF or MI within 6 mo; End-stage renal disease requiring dialysis; Known hereditary degenerative retinal ...