Adverse reactions to taking tadalafil include headache, dizziness, and back pain. Normal doses of tadalafil are generally associated with fewer adverse reactions. Tadalafil has some vasodilatory effect, which may cause a decrease in blood pressure, so some people may experience headache and dizziness after taking it. Back pain may be a case of muscle congestion caused by the medication. Tadalafil is used for erectile dysfunction in men, and this medication should not be combined with nitrates and liothyronine at the same time, such as isosorbide nitrate tablets. The use of this drug is prohibited for those who are allergic to this drug or the components of the formula, exfoliative dermatitis, women. The specific dosage and usage of the above drugs should follow the doctor’s instructions, and should not be used on their own to avoid adverse reactions.