The typicaldose of Viagra is 50 mg. With PAH, high blood pressure develops when a blockage in the arteries within the lung limits normal blood flow. Your healthcare provider will discuss which dose is right for you. This medicine works best when you take it on an empty stomach an hour before sex. Some examples of nitrates are nitroglycerin Nitro-Dur, Nitrostat, others , isosorbide mononitrate Monoket and isosorbide dinitrate Bidil. Tadalafil has been extensively studied for ED. This increase in blood flow results in a firmer, longer-lasting erection.Note: Some pharmacies do not allow the savings card to be used for opioid drugs. How much does tadalafil or cialis cost near you? Find the best tadalafil or cialis prices near . Note: Fraudulent online pharmacies may attempt to sell an illegal generic version of Cialis. These medications may be counterfeit and potentially unsafe. If you purchase medications online, be sure you are buying from a reputable and valid online pharmacy. Ask your health care provider for advice if you are unsure about the online .  · Below, we’ll detail nine of the most common tadalafil interactions to keep in mind. 1. Nitrates. Nitrates are used to treat and prevent angina (chest pain) caused by heart disease. Examples include nitroglycerin (Nitrostat), isosorbide mononitrate (Monoket), and isosorbide dinitrate (Isordil).