The body takes longer to absorb it after a high-fat meal or alcohol. You can take it in a small dose daily or in a larger dose as needed. Do not use a kitchen teaspoon as it will not measure the right amount. These include itraconazole Sporanox, Tolsura , ketoconazole Extina, Ketozole, others and ritonavir Norvir. Remove the syringe from the bottle. If you forget to take it If you have pulmonary hypertension and you forget to take a dose of sildenafil, take it as soon as you remember unless it’s nearly time for your next dose. The following information includes only the average doses of this medicine.Dosage for erectile dysfunction. The recommended dosage of Viagra for erectile dysfunction (ED) is 50 mg, taken as needed about 1 hour before sexual activity. You can take it 30 . If you are experiencing symptoms of ED and are considering a generic version of Viagra, your doctor can prescribe a generic alternative to ensure it is safe and FDA-approved. Sildenafil tablets for erectile dysfunction come in different strengths ranging from 25mg to mg. The usual dose is 50mg, when you need it. Do not take it more than once a day. .