The patients in studies had varying degrees of ED. If you experience a sudden loss of vision in one or both eyes, contact your doctor immediately. Check with your doctor right away if you have a sudden decrease in hearing or loss of hearing, which may be accompanied by dizziness and ringing in the ears. Dosing The dose of this medicine will be different for different patients. If you have an erection that lasts for more than 4 hours, you should go to the nearest hospital emergency department. The mean steady state volume of distribution Vss for sildenafil is L, indicating distribution into the tissues. Do not use this medicine if you are also using a nitrate medicine, often used to treat angina or high blood pressure.Typical dosing for Sildenafil (Viagra) The typical dose is to take 50 mg of sildenafil (Viagra) by mouth, about 1 hour before sex, as needed. The maximum recommended dose is mg. Don’t take sildenafil (Viagra) more than once daily (at any dose). Written by Brian Leonard, PharmD, BCACP, BCGP. AdEnjoy Greater Libido & Performance. Fast Express Shipping. AdWe stock a wide variety of off grid & grid tie solar equipment from controllers to panels. Shop Northern Arizona Wind & Sun for Low Prices, Expert Knowledge & Great Customer ServiceKnowledgeable Staff · Quick & Easy Checkout · 35 Years Running.