Sir, thank you for the excellent series of articles on Oral Medicine – Update for the dental practitioner by Professors Scully and Felix. I refer to the recent one on Red and pigmented lesions (BDJ 2005; 199: 639– 645). The authors make mention of eradication of the mucosal infection in denture stomatitis with concurrent use of chlorhexidine and either miconazole gel, nystatin pastilles or amphotericin lozenges.

I am under the impression that it is generally not advisable to administer chlorhexidine and nystatin concurrently, due to the chlorhexidine-nystatin complexes that form with this combination. It has been suggested in the literature that these salts are the probable reason for the significant difference seen in patients who continued to develop candidal infections after cancer treatment and received chlorhexidine together with nystatin, as compared to patients who received either topical agent alone.

I question whether just because there have not yet been specific studies to prove or disprove the interactions between chlorhexidine and nystatin (or it may just be that I am not aware of any such study) whether we should go against current evidence that would imply that we use chlorhexidine or nystatin alone rather than in combination. Also, would I be mistaken if I suggested that in order to avoid the formation of chlorhexidine-nystatin salts, that chlorhexidine and nystatin could be used at alternative times during the day, rather than at the same time?

The advice and opinion of the authors would be very much appreciated.

Professors Scully and Felix respond: Dr Gaibi makes a fair point. However, in vitro studies do not always reflect the in vivo situation. The minimum inhibitory concentration (MIC) value for the combination of nystatin and chlorhexidine digluconate on Candida albicans used in vitro is significantly higher than the values for each of the drugs alone and thus, in theory the combination of the drugs is less effective, the most likely reason being that a low solubility chlorhexidine-nystatin salt can form.1 However, nystatin and chlorhexidine are used clinically together and with some effect.2 Nevertheless, many patients prefer miconazole because of the taste, it can be purchased over the counter in UK, and it may even prove cheaper ( Table 1 ).

Table 1 Approximate costs of topical antifungals for a two week course, as per BNF 50, 2005.
Full size table