Drugs and Nutrients: Known Issues, Breaking News

Just 20 or 30 years ago, mention of vitamin supplementation caused many health care professionals to talk about creating “expensive urine." Today, however, vitamin and nutrient supplementation has become an important health care intervention.

Drugs and nutrients: increasingly, researchers are finding ways that these 2 entities hold hands to work together. Or, conversely, don’t work together and alter outcomes or cause adverse events.

Just 20 or 30 years ago, mention of vitamin supplementation caused many health care professionals to talk about creating “expensive urine,” implying that vitamins simply pass through the body and are eliminated. Today, however, vitamin and nutrient supplementation has become an important health care intervention.

What have we known for years and what’s breaking news? That’s what this Vitamin and Supplement Condition Center will cover.

To start, many drug— or disease–nutrient relationships have been part of the pharmacist’s basic education for decades. Mineral metabolism is often affected by drugs. For example, diuretics (especially thiazides) and corticosteroids can deplete potassium, increasing susceptibility to digoxin toxicity. Sulfonylureas and lithium impair iodine uptake in the thyroid, tetracyclines reduce iron absorption, and oral contraceptives can depress serum zinc levels.

In addition, many drugs deplete vitamins. Heavy ethanol consumption causes thiamine deficiencies, and isoniazid causes the body to struggle with niacin and pyridoxine metabolism. Oral contraceptives, older antiepileptic drugs, phenothiazines, and nonsteroidal anti-inflammatory drugs (NSAIDs) can reduce folate levels, which in some cases leads to a functional pyridoxine deficiency. These are all known facts and we factor them into our clinical decisions. Often, patients need supplemental vitamins.

Our knowledge of cell biology, human physiology, and how things work at a molecular level far surpasses what we knew 50 years ago. Many experts credit these advances to the push to find cures for AIDS and cancer, efforts that have not been completely successful but have led to new insights. Consequently, we can “see” the cascade of events that occur in cells and cellular processes. What do we see associated with newer drugs?

• Anti-inflammatory drugs have been associated with numerous vitamin deficiencies. Aspirin, for example, can steal vitamins C, K, and pantothenate. Other NSAIDs can reduce available folic acid and melatonin. Case reports of calcium, potassium, zinc, iron, Vitamins B₆, D, K, chromium, glutathione have been published.
• Patients who respond poorly to antidepressants often have folate deficiencies.
• Statins can deplete coenzyme Q₁₀, an enzyme critical for mitochondrial function and energy production. Some researchers believe that depleting coenzyme Q₁₀ increases statin-related side effects. Many prescribers routinely recommend coenzyme Q₁₀ supplementation for their statin patients.
• Patients who have inflammatory disease are often vitamin B₆ deficient. Vitamin B₆ is an important cofactor for more than 100 biochemical reactions, and researchers are now trying to determine if its depletion has a role in increasing cardiovascular risk in patients who take NSAIDs.
• Angiotensin-converting enzyme inhibitors are zinc-dependent dipeptidyl carboxypeptidases; treatment with these drugs may cause zinc deficiency and increase risk of heart failure.

Examining how drugs interact with nutrients is the purview of structure-activity relationship researchers. Daily, clinically significant findings are increasing traffic in the vitamin and supplement aisles. This Condition Center’s purpose is to help you, the pharmacist who needs to help patients determine which indications are evidence-based, make recommendations to patients with confidence.