What special precautions should I follow? Tadalafil can be synthesized starting from D – tryptophan methyl ester and piperonal via a Pictet—Spengler reaction. Do not stop taking tadalafil without talking to your doctor. In trials of the drug, individuals taking Cialis saw a significant reduction in the frequency and urgency of urination and improved urine flow. You can buy it from a store-based pharmacy or reputable online pharmacy with a prescription.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. Tadalafil is in a class of medications called phosphodiesterase (PDE) inhibitors. It works to treat erectile dysfunction by increasing blood flow to the penis during sexual stimulation. This increased blood flow can cause an erection. Tadalafil treats PAH by relaxing the blood vessels in the lungs to allow blood to flow more easily. How to save on generic Cialis There are many ways to save on Cialis, which is available as both a brand-name and generic medication. Save with GoodRx. GoodRx can help you save over 97% off the average retail price of the generic version. Generic Cialis at certain pharmacies is less than $13 with a free GoodRx discount.