Is the prayer of one who takes drugs after 'Isha valid, and is it obligatory for him to perform ghusl every day for prayer?

Drug abuse is a grave sin with dire consequences, and the abuser must immediately quit it as an act of repentance to Allah. He is not required to perform ghusl (major ritual ablution) daily, and his prayer is valid as long as it is free from invalidating factors. The drinker of intoxicants is warned that his prayers will not be accepted for forty days (meaning he will not be rewarded for them), even if they are otherwise valid and sufficient.