How soon after finishing your last terbinafine pill is it safe to start drinking alcohol again?

Any? time: There's no specific time. A rule of thumb would be about 6 hours. Ideally, you would avoid alcohol all together.

Good question: Terbinafine can cause chemical hepatitis & has a 36 hour half life. That means it takes about five days to clear your liver of all terbinafine. Alcohol is a known hepatotoxic substance. Although no clear contraindications are in the package insert for terbinafine, it seems prudent to forgo alcohol or Acetaminophen for a week after last dose of terbinafine to be safe.