It sounds like you're experiencing back pain after taking 20 mg of Tadalafil for a few days, which can indeed be a side effect of this medication.

When taking 20 mg of Tadalafil, some people may experience side effects. Common ones include:

• Headache
• Flushing (redness of the face)
• Nasal congestion (blocked nose)
• Indigestion
• Muscle or back pain

Since you mentioned back pain, this could be related to the medication. It’s important to keep an eye on how severe and persistent the pain is. If the pain is mild and tolerable, it might improve as your body adjusts. However, if the pain becomes severe, lasts a long time, or is accompanied by other symptoms such as chest pain, dizziness, or vision changes, you should seek medical attention promptly.

I recommend discussing this side effect with the doctor who prescribed your medication. They can evaluate your symptoms, consider adjusting your dose, or suggest alternative treatments.

Key points to remember:

• Back pain can be a side effect of Tadalafil.
• Monitor how severe and long-lasting your symptoms are.
• Seek urgent care if you experience severe pain or other concerning symptoms.
• Consult your prescribing doctor for personalized advice and possible medication changes.

Please do not stop or change your medication without consulting your doctor first. If you experience any emergency symptoms, call emergency services immediately.