Humblefish has a thread dedicated to Prazipro, hope this helps.
Prazipro (praziquantel): Treats flukes, black ich, and some internal parasites (worms).
How To Treat - In either a quarantine or display tank, dose
Prazipro at the rate of 1 teaspoon per 20 gallons of water.
DO NOT OVERDOSE (especially with wrasses), try not to mix with other medications (for various reasons), and provide additional gas exchange while treating with Prazi. Wait about a week, do a 20-25% water change and then repeat dosage. The reason for the second dose is to eradicate the “next generation” of worms before they can lay eggs of their own. Because while Prazi does kill worms, it doesn’t eliminate any eggs they might leave behind.
If you are treating a known prazi sensitive species (ex. wrasse), you can run carbon or perform a water change 24 hours after dosing in order to limit exposure time. While praziquantel does remain active in the water column for up to 72 hours, only 24 hours are needed for it to eradicate external worms. Don't forget to still do the second round though!
Prazipro is generally considered reef safe, although it may kill any tube worms/feathers dusters you have. It may also eradicate bristle worms. If you have mass quantities of these, the resulting die-off can lead to an ammonia spike. After treatment is done, activated carbon may be used to remove any residuals (if you need to use a different medication next). If using a protein skimmer post-treatment, be advised that it will “over skim” for at least a couple of weeks.
Pros - Reef safe, effective dewormer that is relatively gentle on most fish.
Cons/Side Effects - Mild appetite suppression, moderate oxygen depletion, wrasses are sensitive to overdosing.
Edit: You can use this treatment calendar to determine when is the best time to add the second dose of Prazipro:
http://www.marineparasites.com/paratreatmentcal.html
