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VIAGRA (sildenafil citrate) Dosage And Administration

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Dosage And Administration

Dosing Considerations

The following factors are associated with increased plasma levels (AUC) of sildenafil:

  • age 65 years or over (40%)
  • hepatic impairment (e.g. cirrhosis: 84%)
  • severe renal impairment (e.g. creatinine clearance <30 mL/min: 100%) concomitant use of potent cytochrome P-450 3A4 inhibitors (e.g. erythromycin: 182%; saquinavir: 210%; ritonavir: 1000%). It can also be expected that more potent cytochrome P-450 3A4 inhibitors such as ketoconazole and itraconazole would result in increased levels of sildenafil.

(see Recommended Dose and Dose Adjustment, ACTION AND CLINICAL PHARMACOLOGY, WARNINGS AND PRECAUTIONS).

VIAGRA (sildenafil citrate) has been shown to potentiate the hypotensive effects of nitrates in healthy volunteers and in patients, and is therefore contraindicated in patients who are taking any type of nitrate drug therapy, or who utilize short-acting nitrate-containing medications, due to the risk of developing potentially life-threatening hypotension. The use of organic nitrates, either regularly and/or intermittently, in any form (e.g. oral, sublingual, transdermal, by inhalation) is absolutely contraindicated (see ACTION AND CLINICAL PHARMACOLOGY, CONTRAINDICATIONS).

Recommended Dose and Dosage Adjustment

For most patients, the recommended dose of VIAGRA is 50 mg taken as needed. The maximum recommended dose is 100 mg. Dosage may be decreased to 25 mg if necessary.

Since higher plasma levels may increase both efficacy and the incidence of adverse events, a starting dose of 25 mg should be considered in patients, age 65 years or over, on concomitant CYPA4 inhibitors, with severe renal impairment, with hepatic impairment and on ritonavir (see Dosing Considerations above, ACTION AND CLINICAL PHARMACOLOGY, WARNINGS AND PRECAUTIONS).

The concomitant use of the potent cytochrome P-450 3A4 inhibitor, ritonavir is associated with a 1000% (11-fold) increase in plasma levels (AUC) of sildenafil. Given the extent of the interaction with patients receiving concomitant therapy with ritonavir, it is recommended not to exceed a maximum single dose of 25 mg of sildenafil in a 48-hour period (see WARNINGS AND PRECAUTIONS).

Administration

To be taken as needed approximately 30 – 60 minutes before sexual activity. However, VIAGRA may be taken anywhere from 0.5 hour to 4 hours before sexual activity. The maximum recommended dosing frequency is once per day.