Notwithstanding any provision of the general statutes, when sentencing a person convicted of a violation of any provision of this chapter, except a violation of subsection (a) or (c) of § 21a-278a, for which there is a mandatory minimum sentence, which did not involve the use, attempted use or threatened use of physical force against another person or result in the physical injury or serious physical injury of another person, and in the commission of which such person neither was armed with nor threatened the use of or displayed or represented by word or conduct that such person possessed any firearm, deadly weapon or dangerous instrument, as those terms are defined in § 53a-3, the court may, upon a showing of good cause by the defendant, depart from the prescribed mandatory minimum sentence, provided the provisions of this section have not previously been invoked on the defendant’s behalf and the court, at the time of sentencing, states in open court the reasons for imposing the particular sentence and the specific reason for imposing a sentence that departs from the prescribed mandatory minimum sentence.