Section 17L. Any coverage offered by the commission to an active or retired employee of the commonwealth insured under the group insurance commission shall provide coverage for abuse deterrent opioid drug products listed on the formulary, compiled pursuant to subsection (b) of section 13 of chapter 17, on a basis not less favorable than non-abuse deterrent opioid drug products that are covered by the commission. An increase in patient cost sharing shall not be allowed to achieve compliance with this section.