Viagra is the common name for sildenafil citrate tablets. Taking this drug is sometimes effective and sometimes ineffective, and there may be reasons such as the drug itself, the individual’s condition, and the dosage, which need to be analyzed specifically. 1. the drug itself: when the use of sildenafil citrate tablets there are differences in product quality, the expiration date of the drug, etc., may affect its pharmacological effect, take the strong drug is effective, take the weak drug is not effective. 2. Individuals: Sildenafil Citrate Tablets work only if they are sexually stimulated, and if they are not sexually stimulated after taking the medicine, they may show no effect. 3. Dosage: when taking sildenafil citrate tablets in different doses, it may lead to the effect when the effective dose is reached and no effect when the effective dose is not reached. To sum up, there are many possible reasons why taking Sildenafil Citrate Tablets may or may not be effective, which should be analyzed under the guidance of a doctor in the light of the actual situation of an individual, and the reasons should be clarified and then the medication should be adjusted accordingly. It should also be noted that sildenafil citrate tablets are suitable for the treatment of erectile dysfunction in men over 18 years of age, and are contraindicated in people who are allergic to them or who are using nitrate drugs such as isosorbide mononitrate, and there may be adverse reactions such as headache and indigestion in the course of the use of this medication. Therefore, those who have the need to use this drug must follow the doctor’s instructions to standardize the use of drugs, in order to strive for a good prognosis. Do not take the drug blindly or increase or decrease the dosage on your own to avoid adverse consequences.