This medicine is available only with your doctor’s prescription. Brand names Why is this medication prescribed? To provide you with the most relevant and helpful information, and understand which information is beneficial, we may combine your email and site usage information with other information we have about you. In , Pfizer scientists discovered that sildenafil, which also inhibits the PDE5 enzyme, caused penile erection in males participating in a clinical study of a heart medicine. Surviving offspring had normal development and reproductive performance. Contraindications Use of Nitrates for example, Nitroglycerine, Isosorbide : may increase hypotensive effects of Nitrates Hypersensitivity reactions to Tadalafil Side Effects Headache, Dyspepsia, Back pain, Myalgia, Nasal pharyngitis, Nasal congestion are common side effects. Cialis reaches its maximum effectiveness two hours after you take it.Generic Cialis, or Tadalafil, is available in several doses in tablet form: milligrams (mg), 5 mg, 10 mg, and 20 mg. Depending on the dose for ED, you can use it as needed before sexual. CIALIS for use as needed: Starting dose: 10 mg up to once daily. Increase to 20 mg or decrease to 5 mg based upon efficacy/tolerability. Improves erectile function compared to placebo up to 36 hours post dose (). CIALIS for once daily use: mg taken once daily, without regard to timing of sexual activity. Best prices for generic cialis on the Internet! The safest way is to ask your physician to try an alternate prescription. Detailed dosage guidelines and administration information for Cialis (tadalafil). Includes dose adjustments, warnings and precautions. Fast Shipping Worldwide.