(a) Any person convicted of a second or subsequent offense under clause (30) of subsection (a) of section 13 of this act¹ or of a similar offense under any statute of the United States or of any state may be imprisoned for a term up to twice the term otherwise authorized, fined an amount up to twice that otherwise authorized, or both.

(b) For purposes of this section, an offense is considered a second or subsequent offense, if, prior to the commission of the second offense, the offender has at any time been convicted under clause (30) of subsection (a) of section 13 of this act or of a similar offense under any statute of the United States or of any state relating to controlled substances.