When should I adjust the dose of tadalafil?

No dosing adjustment are needed for the following  parameters: age, bodymass index (BMI),  smoking, or concurrent diabetes mellitus.  Dosing needs to be adjusted for the following:  Renal insufficiency: (USA Label) No dose adjustment  is required in patients with mild renal  insufficiency. For patients with moderate (creatinine  clearance 31 to 50 mL/min) renal insufficiency,  a starting dose of 5 mg not more than  once daily is recommended, and the maximum  dose should be limited to 10 mg not  more than once in every 48 hours.

For patients  with severe (creatinine clearance <30 mL/min)  renal insufficiency on hemodialysis, the maximum  recommended dose is 5 mg.  Hepatic impairment: For patients with mild or  moderate degrees of hepatic impairment  (Child-Pugh Class A or B), the dose of tadalafil  should not exceed 10 mg once daily. In  patients with severe hepatic impairment  (Child-Pugh Class C), the use of tadalafil has  not been studied.  CYP3A inhibitors: Because CYP3A4 inhibitors  reduce the metabolism of tadalafil, concurrent  use with these agents may increase tadalafil  plasma levels and lengthen the amount of  time that tadalafil levels are detectable. For  patients taking concomitant potent inhibitors  of CYP3A4, such as ketoconazole or ritonavir,  the maximum recommended dose of tadalafil  is 10 mg, and the drug should not be taken  more frequently than once every 72 hours.  Other CYP3A4 inhibitors, such as erythromycin,  itraconazole, and grapefruit juice, would  likely increase tadalafil exposure, although the  specific interactions of these compounds with  tadalafil have not been studied.  Because tadalafil neither inhibits nor  induces the major CYP450 isoforms to a clinically  significant degree, tadalafil is not anticipated  to affect the metabolism of other agents  metabolized by the CYP4503A4 pathway.