Persons with cancer who use herbs or dietary supplements are at risk for harmful drug interactions, a new study has reiterated.

As noted in the International Journal of Clinical Practice report (2012;66[11]:1056-1078), the use of herbs and dietary supplements (HDS) alone or with medications can potentially increase the risk of adverse events experienced by patients with cancer or other diseases. To evaluate documented HDS/drug interactions and contraindications, the investigators conducted a structured literature review that covered a total of 1,491 unique pairs of HDS/drug interactions involving 213 HDS entities and 509 medications.

Overall, HDS/drug interactions and contraindications primarily concerned a relatively small subset of commonly used medications and HDS entities, but the review results may help clinicians identify patients, medications, and HDS products most susceptible to these interactions and contraindications. This, in turn, can help prevent serious adverse events and improve desired therapeutic outcomes for patients with cancer and other diseases.

The analysis of data showed that herbal and botanical remedies were more likely to have documented drug interactions and contraindications than were other dietary supplements studied, such as vitamins, minerals, and amino acids. HDS products containing St. John’s wort, magnesium, calcium, iron, and ginkgo had the greatest number of documented interactions with medications.

Drugs affecting the central nervous system or the cardiovascular system had more documented interactions with HDS. The agents warfarin, insulin, aspirin, digoxin, and ticlopidine had the greatest number of reported interactions with HDS. Nearly half (42.3%) of the 882 HDS/drug interactions described occurred due to altered pharmacokinetics. Just over one-fourth (240) were categorized as major interactions.

Flaxseed, echinacea, and yohimbe had the largest number of documented HDS contraindications.Of the 152 identified HDS contraindications, the most frequent involved gastrointestinal (16.4%), neurologic (14.5%), and renal/genitourinary diseases (12.5%).