What a licensed online pharmacy can offer
Some pharmacy websites operate legally. The FDA’s consumer update, How to Buy Medicines Safely From an Online Pharmacy, says those sites can offer convenience, privacy, and genuine savings, along with safeguards for the purchase. A lawful online pharmacy requires a doctor’s prescription, gives a physical address and a telephone number in the United States, has a licensed pharmacist available for questions, and holds a license from a state board of pharmacy.
That same update describes the sites to leave. Unsafe sellers often advertise prescription drugs at deeply discounted prices and skip the prescription. They may have no U.S. license and no license from your state board, and no pharmacist you can reach. What they ship can be unapproved, counterfeit, or otherwise unsafe: the wrong amount of the active ingredient, a different ingredient, or a product stored outside the controls a licensed pharmacy uses. A familiar page does not show where the tablets were made.
A site that will sell tadalafil with no prescription is the warning sign. Leave it.
Look the pharmacy up on BeSafeRx
The prescription can come from an office visit or from telehealth, provided a clinician actually writes it. Either route ends at a named pharmacy. Before you pay a pharmacy you do not already use, open BeSafeRx. BeSafeRx is the FDA campaign for buying prescription medicines online, and it includes a location tool for state board of pharmacy license databases. If the pharmacy is not listed, do not use it.
Hold payment if the site has no U.S. address and phone, no pharmacist, or ships medicine in broken packing, with no expiration date, or in a carton you cannot read. A price that seems too good to be true is an FDA warning sign. Check the license before you treat the discount as real.
Cialis, generic tadalafil, and Adcirca
Cialis tablets contain tadalafil. On the U.S. label they are indicated for erectile dysfunction, for the signs and symptoms of benign prostatic hyperplasia, and for both together. When the prescription is for erectile dysfunction, generic tadalafil is that same active ingredient under a generic name. The order should name the product, the strength, and whether you take it as needed or once a day. Generic equivalence for this drug class explains how an approved generic is judged against the brand.
Adcirca is tadalafil labeled for pulmonary arterial hypertension. Keep it out of an erectile-dysfunction order. Do not combine Cialis with Adcirca or with another phosphodiesterase 5 (PDE5) inhibitor. The Cialis prescribing information includes a section on combination with other PDE5 inhibitors or other erectile-dysfunction therapies. Sildenafil and vardenafil are separate prescriptions, each with its own timing. Adding either one to tadalafil stacks the same class.
A known serious hypersensitivity to tadalafil, whether the reaction was to Cialis or to Adcirca, is a reason to stop before the fill.
As needed for up to 36 hours, or a small daily dose
Tell the prescriber which pattern you actually use. If sex is something you can plan, the erectile-dysfunction label starts as-needed Cialis at 10 mg, taken before sexual activity. When that dose is not enough, it may be increased to 20 mg. When it is hard to tolerate, it may be decreased to 5 mg. The maximum is once per day. Food does not change the instruction: Cialis may be taken without regard to food. On the label, as-needed tadalafil improved erectile function compared with placebo for up to 36 hours after the dose. Those hours are the window in which sexual activity can benefit. They do not raise the once-a-day limit, so a second tablet later the same day is past the maximum.
If you do not want to time a tablet to sex, once-daily Cialis for erectile dysfunction is the other order. It starts at 2.5 mg once a day, without regard to when you expect to be sexually active, and it may be increased to 5 mg based on effect and tolerability. The daily tablet is already that day’s dose. Leave the 10 mg and 20 mg tablets off that regimen.
Read the directions before you accept a 5 mg bottle. That strength can be the reduced as-needed dose or the increased once-daily erectile-dysfunction dose. For prostate symptoms, alone or with erectile dysfunction, the once-daily dose is 5 mg at about the same time every day.
Nitrates, then riociguat
Do not take Cialis if you use any form of organic nitrate. Nitrates treat angina, pain in the chest, jaw, or arm from heart disease. They include nitroglycerin tablets, sprays, ointments, pastes, and patches, and medicines such as isosorbide dinitrate and isosorbide mononitrate. Cialis can make the blood-pressure drop from a nitrate sudden and severe. The label contraindicates the combination.
The 48-hour interval is for a life-threatening emergency, and someone else runs it. If Cialis has already been taken and a nitrate is judged medically necessary, at least 48 hours should pass after the last dose, including after an as-needed dose, before a nitrate is considered. Even then, the nitrate should be given only under close medical supervision, with blood-pressure monitoring.
Riociguat has its own line in the contraindications. Do not use Cialis with a guanylate cyclase stimulator such as riociguat (Adempas), a medicine for pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension. Cialis may deepen the drop in blood pressure these stimulators can cause. If you are unsure whether one of your medicines is a nitrate or a guanylate cyclase stimulator, ask the prescriber or the pharmacist before anyone fills the order.
Do not start Cialis when sex itself is inadvisable because of cardiovascular status.
A lower price still has to be a licensed fill
Brand versus generic, the strength, and the schedule change what a licensed pharmacy charges, and so does a discount on that exact order. Compare the prescription line with the pharmacy’s price for the same product and the same directions. Convenience, privacy, and genuine savings belong with the prescription and the license. A deep discount that appears only because the site skips the doctor is the unsafe pattern in the FDA guide.
Then fill
Arrange the prescription with a clinician who can prescribe where you live. Check the dispensing pharmacy on BeSafeRx, and with the state board when you have the pharmacy’s name. Confirm whether the directions say as needed or once daily, and stop the order if organic nitrates or riociguat are already in use. Then pay the licensed pharmacy. For how sexual arousal and blood flow fit this class of medicine, see erectile dysfunction pharmacology.
Health Pharmacology Formulary Desk. Reviewed 23 October 2026 against the DailyMed Cialis prescribing information, FDA BeSafeRx, and the FDA guide on how to buy medicines safely from an online pharmacy.