Understanding Drug-Nutrient Interactions: An Overview

"As Americans consume increasingly complex combinations of prescription medications and nutritional supplements, the concern for adverse events attributable to interactions between them increases accordingly." — Christopher Borgert, PhD, president of Applied Pharmacology and Toxicology - Gainesville, Fla.

If you are one of the nearly 80 percent of chiropractors who recommend and sell nutritional supplements to patients, it is important to understand the basic mechanisms of these potential interactions and the at-risk population so you can act accordingly.

Between 1994 and 2006, the number of adult Americans who reported using at least one nutritional supplement jumped from 42 percent to 53 percent, according to the CDC.¹ Most experts agree that currently, as many as 60 percent of American adults use at least one nutritional supplement. It is also well-documented that at least 50 percent of U.S.  adults take one prescription medication, and that close to 20 percent take three.² Several reports have also demonstrated that many prescription drug users are also taking nutritional supplements in conjunction with these medications. In fact, over 50 percent of people using at least one nutritional supplement combine this use with a drug.³

Put into perspective, if these 2006 statistics are true today, then at the very least, 15 million Americans are at risk for a potential drug-nutrient interaction.⁴

Patients Most at Risk

While it is important to consider the potential for drug-nutrient interactions with all of your patients, those at highest risk include patients with a chronic disease process (e.g., inflammatory condition); patients on multiple medications; patients with genetic variances with drug metabolism; patients with impaired organ function; patients at the end of the age spectrum; and patients who consume nutritional supplements on a chronic basis.

Mechanisms of Interaction

Drug-nutrient interactions occur in the body through a pharmacokinetic or pharmacodynamic mechanism. A pharmacokinetic interaction occurs because of one of the following mechanisms:⁴

• Alteration of drug absorption
• Induction or inhibition of a drug-metabolizing enzyme
• Altered drug protein binding
• Altered drug excretion

Pharmacokinetics is also the focal point of research on drug-nutrient interactions, as these mechanisms are responsible for the disposition of the drug / nutrient as it is processed in the intestine and liver. It is important to understand that a pharmacokinetic interaction can be antagonistic or synergistic and that any substance (natural product) may interact with a drug by altering any one or combination of these systems.

Pharmacokinetic interactions most commonly occur because the nutritional supplement has an impact on one of the following drug-metabolizing enzymes or drug transporters, causing either an increase in the drug's toxicity or decrease in the drug's efficacy, both of which can have an impact on the patient's health:

Drug-metabolizing enzymes: cytochrome P450 (CYPs); uridine diphosphoglucurony^l transferases (UGTs); and glutathione S-transferases. Drug transporters: P-glycoprotein; organic anion transporting polypeptides (OATPs).

A pharmacodynamic interaction is the result of an additive, synergistic or antagonistic effect of the supplement's physiological properties in combination with the drug's properties. A classic example is when medications that have antiplatelet activity are combined with a nutritional supplement with antiplatelet activity, potentially leading to increased bleeding.

Not all drug-nutrient interactions result in a negative outcome. Many supplements may be recommended as a beneficial addition to help improve the target action of a medication based on their pharmacodynamic properties.

It is important to analyze all of the medications and nutritional supplements patients consume. It is perhaps equally important to document results in a manner that exhibits due diligence from a medicolegal standpoint. If you make supplement recommendations, every patient history should include questions about drug-nutrient use and advice should be dispensed accordingly.

References

1. www.cdc.gov/nchs/data/databriefs/db61.htm
2. www.cdc.gov/nchs/data/hus/hus05.pdf
3. Gardiner P, et al. Factors associated with dietary supplement use among prescription medication users. Arch Intern Med, 2006.
4. Boullata J. Natural health product interactions with medication. Nut Clin Pract, 2005.