Viagra is always taken as needed, usually an hour before having sex. An erection will not occur just by taking a pill. Grapefruit may interact with tadalafil and lead to unwanted side effects. There is also the option to take Cialis as needed. Cialis lasts longer.We have good news for you: generic Cialis, used to treat erectile dysfunction (ED) and enlarged prostates, just hit pharmacies. Prices for the generic, Welcome! You’re in GoodRx Provider Mode. Now, you’ll enjoy a streamlined experience created specifically for healthcare providers. Learn more about Provider Mode close . The drug comes in low-dose versions that can be taken daily. This means you can have sex at any time, rather than needing to take a pill from time to time as needed like other ED brands. The starting dose for daily-use Cialis is milligrams (mg). If that doesn’t work, you can increase your daily dose up to 5 mg. The recommended starting dose for Cialis intended for once daily use is mg, take at the same time each day, without regard to timing of sexual activity. This may be increased to 5mg/day based on need and tolerability. May be taken with or without food. Cialis is available as a generic, under the name tadalafil. 3.