Hugh Hefner's widow and children must stay away from drugs to inherit his fortune.

The Playboy founder - who died in September aged 91 - stipulated in trust document that if the beneficiaries to his estate, wife Crystal and his kids Christie, David, Marston and Cooper, frequently use illegal substances or become dependent on alcohol or any drugs, they will be suspended from it.

The documents, which were obtained by The Blast, state: ''If the trustees reasonably believe that a beneficiary of any trust routinely or frequently uses or consumes any illegal substance so as to be physically or psychologically dependent upon that substance, or is clinically dependent upon the use or consumption of alcohol or any other legal drug or chemical substance that is not prescribed by a board certified medical doctor or psychiatrist in a current program of treatment supervised by such a doctor or psychiatrist, and if the Trustees reasonably believe that as a result the beneficiary is unable to care for himself or herself, or is unable to manage his or her financial affairs, all mandatory distributions (including distributions upon termination of the trust) to the beneficiary, all of the beneficiary's withdrawal rights, and all of the beneficiary's rights to participate in decisions concerning the removal and appointment of Trustees will be suspended.''

The documents also state that trustees may request a drug test from a beneficiary they suspect of abusing illegal substances.

If a trustee is suspended, they may have their rights to the trust restored after a 12 month period of sobriety.

The documents explained: ''[Rights to the trust may be restored] in the case of use or consumption of an illegal substance, examinations indicate no such use for 12 months and, in all cases, when the Trustees in their discretion determine that the beneficiary is able to care for himself or herself and is able to manage his or her financial affairs.''

The media mogul - who established the trust in May 1991 and was initial trustee until his death - also disinherited and excluded from the trust ''any person who claims to be a child of mine, including any child of mine conceived after my death, unless such child lived with me in my household and was acknowledged by me in writing to be my child.''

Marston, 27, and Cooper, 26, cannot become co-trustees until they reach the age of 30.