Herb-drug interactions put many cancer patients at risk

Due to polypharmacy combined with the rising popularity of so-called alternative medicines (SCAM), oncology patients are at particular risk of drug-drug interactions (DDI) or herb-drug interactions (HDI). Caution is therefore indicated.

The aims of this study were to assess DDI and HDI in outpatients taking oral anticancer drugs.

All prescribed and non-prescribed medications, including SCAM, were prospectively collected by hospital pharmacists during a structured interview with the patient. DDI and HDI were analyzed using four interaction software programs: Thériaque^®, Drugs.com^®, Hédrine, and Memorial Sloan Kettering Cancer Center (MSKCC) database. All detected interactions were characterized by severity, risk, and action mechanism. The need for pharmaceutical intervention to modify drug use was determined on a case-by-case basis.

294 patients were included, with a mean age of 67 years. The median number of chronic drugs per patient was 8 [1-29] and 55% of patients used at least one SCAM. At least 0ne interaction was found for 267 patients (90.8%): 263 (89.4%) with DDI, 68 (23.1%) with HDI, and 64 (21.7%) with both DDI and HDI. Only 13% of the DDI were found in Thériaque^® and Drugs.com^® databases, and 125 (2.5%) were reported with a similar level of risk on both databases. 104 HDI were identified with only 9.5% of the interactions found in both databases. 103 pharmaceutical interventions were performed, involving 61 patients (20.7%).

The authors concluded that potentially clinically relevant drug interactions were frequently identified in this study, showing that several databases and structured screening are required to detect more interactions and optimize medication safety.

This figure of potential HDIs is high – much higher than in most previous studies. A possible explanation could be that the study was carried out in France where the use of herbal remedies is considerable. As some HDIs can cause serious problems for patients, my advice is to think twice about using herbal remedies while taking prescription drugs. I think this advice is sound regardless of whether someone is suffering from cancer or any other condition.