Patient in hospital signs separation agreement

If my wife in the hospital on a mind-altering drug (Fentanyl) signs a separation agreement, will it be valid? Should I wait 24 hours after she is off of the drug?

She can contest the validity of the separation agreement on grounds that she was incapacitated at the time of signing. If you want to avoid any issue with your wife contesting the validity of the separation agreement, I would wait until she is no longer hospitalized or medicated so that she can’t raise lack of capacity as a defense to the validity of your separation agreement.