Sildenafil dosing

Sildenafil doses should be decreased when any potent cytochrome P450 3A4 inhibitor is used (e g., cimetidine, erythromycin, clarithromycin, ketoconazole, itraconazole, ritonavir, and saquinavir). Vardenafil doses vary accordingto which agent is used (2.5 mg q 72 h for ritonavir, 2.5 mg q 24 h for indinavir, ketoconazole 400 mg daily, and itraconazole 400 mg daily and 5 mg q 24 h for ketoconazole 200 mg daily, itraconazole200 mg daily, and erythromycin). Tadalafil doses are reduced only when it is used with the most potent cytochrome P450 3A4 inhibitors (e g., ketoconazole or ritonavir). 

Renal function impairment In volunteers with severe renal impairment (Ccr 30 mL/min or less), sildenafil clearance was reduced. Consider an initial sildenafil dose of 25 mg in these patients. There is no clinical data on the safety or efficacy of vardenafil in patients with end-stage renal disease requiring dialysis. 

For sildenafil, the manufacturers recommend that a low starting dose of sildenafil 25 mg should be considered in patients with erectile dysfunction taking inhibitors of CYP3A4 such as erythromycin. For pulmonary hypertension, the UK manufacturer says that a downward reduction of the sildenafil dose to 20 mg twice daily should be considered with erythromycin, and 20 mg once daily with clarithromycin or telithromycin, (however, note that erythromycin had a greater effect than clarithromycin in the studies above) whereas the US manufacturer says that no dose adjustment is needed with erythromycin. ... 

For maximal absorption, patients should avoid taking sildenafil or vardenafil with a fatty meal. A fatty meal does not affect absorption of tadalafil. / If the first dose is not effective, patients should continue trying for five to eight doses. Some patients benefit from titration up to 100 mg of sildenafil, 20 mg of vardenafil, or 20 mg of tadalafil. 

Sildenafil and vardenafil decrease systolic/diastolic blood pressure by 8 to 10/5 to 6 mm Hg for 1 to 4 hours after a dose. Although most patients are asymptomatic, multiple antihypertensives, nitrates, and baseline hypotension increase the risk of developing adverse effects. Although tadalafil does not decrease blood pressure, it should be used with caution in patients with cardiovascular disease because of the inherent risk associated with sexual activity. 

One additional medication that has recently been studied is sildenafil, which is more commonly known by its trade name Viagra. Sildenafil is taken at doses from 50 to 100 mg per dose about 1-2 hours before sex. Sildenafil is sometimes effective but its expense and potential complications in patients with heart disease limit its usefulness. It can be quite useful in males who experience erectile dysfunction, though it does not improve delayed ejaculation. 

SILDENAFIL 50 mg taken as needed approximately 1 hour before sexual activity. However, sildenafil may be taken anywhere from 4 hours to 30 minutes before sexual activity. Based on effectiveness and tolerance, the dose may be increased to a maximum recommended dose of 100 mg or decreased to 25 mg. The maximum recommended dosing frequency is once per day. 

Concomitant use with protease inhibitors Do not exceed a maximum single dose of 25 mg of sildenafil within a 48-hour period. 

Concomitant use with alpha-blockers Do not take 50 or 100 mg doses of sildenafil within 4 hours of alpha-blocker administration. A 25 mg dose of sildenafil may be taken at any time. 

Isosorbide Dinitrate Hydralazine (BiDil) [Antianginal, Antihypertensive/Vasodilator, Nitrate] Uses HF in African Amer-icans improve survival functional status, prolong time between hospitalizations Action Relaxes vascular smooth muscle peripheral vasodilator Dose Initially 1 tab tid PO (if not tol ated reduce to 1/2 tab tid), titrate >3-5 d as tolerated Max 2 tabs tid Caution [C, /-] recent MI, syncope, hypovolemia, hypotension, hep impair Contra For children, concomitant use w/ PDE5 inhibitors (sildenafil) Disp Tabs SE HA, dizziness, orthostatic hypotension, sinusitis, GI distress, tach, paresthesia, amblyopia Interactions t Risk of severe hypotension W/ antihypertensives, ASA, CCBs, MAOIs, phenothiazides, sildenafil, tadalafil, vardenafil, EtOH X pressor response Wf i -1- effects W7 NSAIDs EMS Use ASA, antihypertensives and CCBs w/ caution, may t hypotension concurrent Viagra-type drug use can lead to profound hypotension concurrent EtOH use can t effects OD May cause N/V, profound hypotension, skin flushing, HA from ICP, bradycardia, confusion, and circulatory collapse activated charcoal may be effective, epi use is contraindicated... 

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