If Penegra 100 mg contains sildenafil 100 mg, it can seem to “lose effectiveness” for several reasons. It does not usually stop working simply because you have used it repeatedly. Common reasons it may work less well Timing: Sildenafil is usually taken about 1 hour before sex; it can be taken 30 minutes to 4 hours beforehand. M MedlinePlus +1 Heavy/fatty meal: A high-fat meal can delay absorption and make the onset slower. D DailyMed Insufficient sexual stimulation: Sildenafil helps the natural erection Penegra 100 mg   it does not automatically produce an erection without sexual stimulation. Alcohol, stress, anxiety, or tiredness: These can make erections more difficult even when the medicine is working. Underlying health changes: Diabetes, high blood pressure, high cholesterol, hormonal problems, and some medications can contribute to worsening ED. N nhs.uk Counterfeit or poor-quality tablets: This is a concern if the medicine comes from an unreliable source. N nhs.uk 100 mg is already the maximum recommended single dose for sildenafil, and it should not be taken more than once in 24 hours. D DailyMed Don't increase the dose yourself or combine it with Tadalis/tadalafil. If you tell me how long Penegra 100 mg has been working for you and what happens now (no erection, weak erection, or erection doesn't last), I can help identify the likely reason.