If Tadasoft 20 mg contains tadalafil 20 mg, use should be stopped and medical advice sought in certain situations: Erection lasting more than 4 hours: seek emergency treatment immediately. Sudden loss of vision: stop tadalafil and seek medical attention promptly. Sudden decrease or loss of Tadasoft 20 mg  : stop tadalafil and seek prompt medical care. Serious or persistent side effects: contact a healthcare professional before taking another dose. If you are prescribed nitrates or certain interacting medicines: tadalafil should not be used with nitrates because of the risk of a dangerous blood-pressure drop. For ongoing ED treatment, don't decide to continue, increase, or discontinue long-term use solely based on online advice; have the treatment reviewed by a qualified healthcare professional.