Is it permissible for a sick person who is taking a narcotic medication that affects their sleep and wakefulness to combine prayers and perform some of them with tayammum, then repeat them if they are able to perform ghusl after the time has expired?

It is permissible to sleep before the time for prayer begins, and there is no sin in missing it while asleep. It is not permissible to perform tayammum (dry ablution) if one is able to use water. However, if a worshipper fears that the prayer time will expire by using water, the Malikis permit tayammum. As for the majority of scholars, they hold that using water is obligatory, even if the time for prayer expires, and this is the fatwa. If there is no fear of the time expiring, then tayammum is not permissible if water is available. There is a difference of opinion regarding the obligation to repeat the prayer performed with tayammum in such a case. A sick person for whom making up the prayer is difficult may act upon the opinion of those who do not deem it obligatory.