Cialis is not recommended for people taking any form of nitroglycerin because the combination may lower blood pressure to an unsafe level. Resources and support See the Healthy Male site for more information about erectile dysfunction and its treatment. What important information should you know about Cialis? What if I am taking other drugs? Cialis will be available as oral tablets in 5mg, 10mg and 20mg strengths. Will Cialis be prescription or OTC over-the-counter? Prolonged erections can be dangerous.Three Cialis mg to 5 mg subjects, three Cialis 5 mg subjects and two placebo subjects discontinued study participation due to an adverse event (AE). Nasal congestion was the only AE leading to discontinuation reported by more than one subject (two subjects in the tadalafil to 5 mg group). Brand-name Cialis: $ per month (5mg) Generic Cialis (tadalafil): starting at $40 per month (5mg, 10mg, 20mg) Daily generic Cialis (tadalafil): starting at $40 per . Tadalafil (Cialis) is available both as brand-name and generic tablets. Common side effects of this medication include headache and indigestion. Tadalafil .