An interesting increase in immediate and residual efficacy of a trade mark of alcoholic 2% chlorhexidine gluconate, with and without dye, has been demonstrated by an in vitro study with ATCC micro-organisms and strains isolated from ICU patients

Aim: ChloraPrep™ (CHP) is a clear solution of 2% (w/v) chlorhexidine (CHG) in 70% (v/v) isopropyl alcohol (IPA) administered with a specially designed sterile single-use applicator in which a tinting agent can be added to the CHP solution upon activation of applicator immediately prior to patient skin preparation (CHP+T). This study investigated whether the immediate and residual efficacy of CHP vs CHP+T and a stock solution of 2% CHG in 70% IPA varied, and whether CHP was compromised by the addition of the dye.

Methods and results: We compared the immediate and residual activity (in 1 min) of 70% IPA with that of 2% CHG in 70% IPA stock solution prepared in the laboratory against CHP+T and CHP, against 22 micro-organisms (5 ATCC and 18 clinical isolates) on germ-carriers. CHP and CHP+T demonstrated superior immediate and residual efficacy compared to the 70% IPA plus 2% CHG in 70% IPA stock solutions. Each antiseptic tested showed greater efficacy against the Gram-positive bacteria than against the Gram-negative bacteria. However, their antimicrobial effect on yeasts was even lower.

Conclusions: CHP and CHP+T have superior immediate and residual efficacy compared to stock 70% IPA and 2% CHG in 70% IPA solutions, and CHP+T is not affected by the tinting agent.

Significance and impact of the study: ChloraPrep is a product which can be stained just before use. We have demonstrated that the immediate and residual efficacy of the antimicrobial solution is not compromised by the dye. The efficacy of CHP is greater against bacteria than against yeasts obtained from ICU patients. Interestingly, CHP is more effective against bacteria than a formula made in the laboratory with the same basic components (2% chlorhexidine and 70% IPA). The intermittent heat sterilization process of the commercial preparation might hypothetically have improved the residual activity of the CHP solutions.