What is the minimum hours can you wait in between doses of Viagra?

The answer you are looking for: https://www.drugs.com/pro/viagra.html
Below is a quote from the above.
"Dosage Information

For most patients, the recommended dose is 50 mg taken, as needed, approximately 1 hour before sexual activity. However, Viagra may be taken anywhere from 30 minutes to 4 hours before sexual activity.

The maximum recommended dosing frequency is once per day.

Based on effectiveness and toleration, the dose may be increased to a maximum recommended dose of 100 mg or decreased to 25 mg."

You should only take one and, beware all drugs have side effects, good luck to you.