(a) Any person convicted of a third or subsequent offense under this chapter, except for violations of § 21-28-4.01(c)(2)(iv), § 21-28-4.01(c)(2)(v), or § 21-28-4.01(c)(2)(vi), may be imprisoned for a term up to three (3) times the term authorized, and fined an amount up to three (3) times that authorized by § 21-28-4.11, or both.
(b) For purposes of this section, an offense is considered a third or subsequent offense if, prior to his or her conviction of the offense, the offender has at any time been convicted twice under this chapter, except for violations of § 21-28-4.01(c)(2)(iii), § 21-28-4.01(c)(2)(iv), § 21-28-4.01(c)(2)(v), or § 21-28-4.01(c)(2)(vi), or twice under any statute of the United States or of any other state, or any combination of them, relating to narcotic drugs, marijuana, depressant, stimulant, or hallucinogenic drugs.