They will be repriced appropriately as the number of shares per option will be adjusted from 100 to 20.
Reverse split usually happens when the company and the stock are in trouble so you should be very profitable!
The liquidity will dry up in these going forward as other Traders will want to trade standard options. This happens all the time in leveraged ETF's which use options to generate the leverage on a daily basis and thus significant decay over the year. Those puts should be held to expiry and just buy the stock to liquidate or exercise early to lock in profits. They will send you a notice to explain the new structure of the options so read this to know how they will trade.