If Fildena CT 50 mg contains sildenafil 50 mg, its dosage may need adjustment when sildenafil levels could become higher or when side effects occur. Common situations include: Age over 65: A lower starting dose of 25 mg may be considered. Severe kidney impairment: A 25 mg starting dose may be appropriate because sildenafil exposure can increase. Liver impairment: A lower starting dose may be considered. Certain drug interactions: Strong CYP3A4 inhibitors such as ketoconazole, itraconazole, or erythromycin can increase sildenafil levels, so 25 mg may be considered initially. Alpha-blocker treatment: Sildenafil is generally started at 25 mg in patients taking alpha-blockers who are stable on that treatment. Ritonavir use: The recommended sildenafil dose is 25 mg, with a maximum of 25 mg in a 48-hour period. The usual sildenafil dose for ED is 50 mg as needed, with adjustment based on effectiveness and tolerability; it should not be taken more than once daily. Do not change Fildena CT 50 mg yourself. A doctor or pharmacist should determine whether a lower, higher, or different treatment is appropriate, particularly if you take other medicines or have kidney, liver, or cardiovascular conditions.