Cialis is the trade name, generic name tadalafil, should not be taken 40mg at a time, exceeding the maximum use of 20mg, should be used in the instructions and under the guidance of a doctor. Tadalafil is a cyclic guanosine monophosphate-specific phosphodiesterase inhibitor that promotes penile erection in the presence of sexual stimulation. The general recommended dose of tadalafil is 10mg/dose, which can be adjusted according to the efficacy of the drug, patient tolerance, and generally up to 20mg/dose, which can be taken on demand at least half an hour before sexual activity. Tadalafil should not be used in combination with nitrates, and should be used by patients with cardiac disease after consulting a cardiologist, given the potential risk to the heart from sexual activity. Adverse reactions such as back pain, myalgia, nasopharyngitis, and dyspepsia may occur during tadalafil use. Tadalafil should be used according to the instructions or as prescribed by the doctor, do not increase the dose at your own discretion to prevent discomfort.