(2) Recklessness. A person is reckless with respect to an element of an offense even though his disregard thereof is not conscious, if his not being conscious thereof is due to self-induced intoxication.
(3) When a Defense. Intoxication which (a) is not self-induced, or (b) if self-induced, is grossly excessive in degree, given the amount of the intoxicant, to which the actor does not know he is susceptible, is an affirmative defense if by reason of such intoxication the actor at the time of his conduct lacked substantial capacity either to appreciate its criminality or to conform his conduct to the requirements of law.
(4) Definitions. In this section:
(b) "self-induced intoxication" means intoxication caused by substances which the actor knowingly introduces into his body, the tendency of which to cause intoxication he knows or ought to know, unless he introduces them pursuant to medical advice or under such circumstances as would otherwise afford a defense to a charge of crime.