You should also call your insurance company to see if they cover erectile dysfunction medications. Which Is More Effective? Tadalafil treats PAH by relaxing the blood vessels in the lungs to allow blood to flow more easily. This medicine also works best when you take it an hour before sex on an empty stomach. However, safety should always be the top priority. Cialis should not be used by patients taking nitrates such as nitroglycerin tablets or patches because the combination of these with Cialis could significantly lower blood pressure and lead to fainting or even death in some men. Always discuss with your health care practitioner ALL of the medications you are taking prescription and over-the-counter that way, you can receive the best advice for your own situation.Cialis lasts up to 36 hours in the body, while Viagra lasts 4–6 hours in the body. Both are taken 30 minutes before sex. Cialis can cause limb pain, while Viagra can cause vision change, rash. Tadalafil is a generic version of the prescription drug Cialis. Doctors prescribe it to treat erectile dysfunction and benign prostatic hyperplasia. It helps relieve erectile dysfunction by. Cialis comes in several different strengths, including: milligrams (mg) 5 mg. 10 mg. 20 mg. The cost for these different strengths depends on whether you have insurance, your individual plan.