🍓Medical Nutrition Therapy II Unit 15 – Drug-Nutrient Interactions & Medication

Key Concepts and Definitions

• Drug-nutrient interactions occur when a drug affects the absorption, metabolism, or excretion of a nutrient or when a nutrient affects the absorption, metabolism, or action of a drug
• Pharmacodynamics refers to the biochemical and physiological effects of drugs on the body, including the mechanisms of drug action and the relationship between drug concentration and effect
• Pharmacokinetics describes how the body affects a drug, including the processes of absorption, distribution, metabolism, and excretion (ADME)
• Bioavailability is the fraction of an administered dose of a drug that reaches the systemic circulation and is available at the site of action
• Half-life represents the time required for the concentration or amount of drug in the body to be reduced by one-half
  • Drugs with shorter half-lives may need to be administered more frequently to maintain therapeutic levels
• Therapeutic index is a comparison of the amount of a drug that causes the therapeutic effect to the amount that causes toxicity, with a higher therapeutic index indicating a safer drug
• Adverse drug reactions (ADRs) are unintended, harmful reactions to a medication, which can range from mild to severe and may be influenced by factors such as age, genetics, and nutritional status

Types of Drug-Nutrient Interactions

• Pharmacokinetic interactions affect the absorption, distribution, metabolism, or excretion of a drug or nutrient
  • Examples include altered gastric pH affecting drug absorption (antacids and antibiotics) and competition for transport proteins (warfarin and vitamin K)
• Pharmacodynamic interactions occur when a nutrient alters the pharmacological effect of a drug at its site of action
  • For instance, vitamin K can antagonize the anticoagulant effects of warfarin by promoting blood clotting
• Physicochemical interactions happen outside the body, such as when a drug binds to a nutrient in the gastrointestinal tract, reducing its absorption
  • Tetracycline antibiotics can chelate with calcium, magnesium, and iron, forming insoluble complexes and decreasing their absorption
• Physiological interactions involve indirect effects on the body's functions, such as a drug causing nausea and vomiting, leading to nutrient malabsorption
• Drug-alcohol interactions can be significant, as alcohol can enhance or inhibit drug metabolism and increase the risk of adverse effects
  • Combining alcohol with acetaminophen can lead to severe liver damage
• Drug-herb interactions are becoming more common with the increased use of herbal supplements and can result in altered drug efficacy or toxicity
  • St. John's wort can induce cytochrome P450 enzymes, reducing the effectiveness of many drugs, including oral contraceptives and anticoagulants

Common Medications and Their Nutritional Effects

• Proton pump inhibitors (PPIs) used for acid reflux can decrease the absorption of calcium, magnesium, iron, and vitamin B12 by reducing stomach acid
• Metformin, a common diabetes medication, can cause vitamin B12 deficiency by impairing its absorption in the ileum
• Statins used to lower cholesterol can deplete coenzyme Q10 (CoQ10) levels, as both share the same biosynthetic pathway
  • Low CoQ10 levels may contribute to statin-induced myopathy and muscle pain
• Diuretics like furosemide can lead to potassium, magnesium, and zinc deficiencies by increasing their excretion in the urine
• Antibiotics can disrupt the gut microbiome, leading to diarrhea and malabsorption of nutrients like vitamin K and B vitamins
• Corticosteroids used for inflammation can cause calcium and vitamin D deficiencies, increasing the risk of osteoporosis
• Antidepressants like selective serotonin reuptake inhibitors (SSRIs) can cause weight gain and alter appetite, potentially affecting overall nutrient intake

Nutrient Impact on Drug Efficacy

• High-fat meals can enhance the absorption of lipophilic drugs like propranolol and griseofulvin, while delaying the absorption of hydrophilic drugs like acetaminophen
• Grapefruit juice can inhibit cytochrome P450 3A4 enzymes, leading to increased bioavailability and toxicity of drugs like statins, calcium channel blockers, and immunosuppressants
• Vitamin K intake can counteract the effects of warfarin, an anticoagulant, by promoting blood clotting
  • Patients on warfarin should maintain a consistent intake of vitamin K-rich foods to avoid fluctuations in INR (International Normalized Ratio)
• High-dose vitamin C supplements can interfere with the metabolism and elimination of acetaminophen, increasing the risk of liver toxicity
• Calcium and iron supplements can reduce the absorption of antibiotics like tetracyclines and fluoroquinolones by forming insoluble complexes
• Folate supplementation can mask vitamin B12 deficiency and exacerbate neurological damage in patients with pernicious anemia
• Potassium-rich foods like bananas and potatoes can enhance the potassium-sparing effects of ACE inhibitors and increase the risk of hyperkalemia

Assessment of Drug-Nutrient Interactions

• Obtain a comprehensive medication history, including prescription drugs, over-the-counter medications, herbal supplements, and vitamins
• Review the patient's diet history and nutrient intake, paying attention to any nutrient deficiencies or excesses that may interact with medications
• Monitor laboratory values related to drug efficacy and safety, such as INR for warfarin, potassium levels for diuretics, and liver function tests for acetaminophen
• Assess for signs and symptoms of adverse drug reactions or nutrient deficiencies, such as muscle pain with statins or anemia with metformin
• Consider pharmacogenetic testing to identify genetic variations in drug-metabolizing enzymes that may affect drug response and nutrient interactions
  • For example, patients with CYP2C9 polymorphisms may require lower doses of warfarin and be more sensitive to vitamin K intake
• Collaborate with healthcare providers to adjust medication doses or nutrient intake based on the assessment findings and patient's individual needs
• Educate patients on potential drug-nutrient interactions and strategies to manage them, such as timing of medication and meal intake or avoiding certain food-drug combinations

Dietary Strategies for Managing Interactions

• Space the administration of medications and nutrient supplements at least 2-4 hours apart to minimize physicochemical interactions
  • For example, take calcium supplements at least 2 hours before or after taking a tetracycline antibiotic
• Encourage a balanced and varied diet to ensure adequate nutrient intake and minimize the impact of drug-induced nutrient deficiencies
  • Patients on PPIs may benefit from consuming calcium-rich foods like dairy products, leafy greens, and fortified foods
• Recommend nutrient supplements when dietary intake is insufficient or drug-nutrient interactions are unavoidable
  • Patients on metformin may require vitamin B12 supplementation to prevent deficiency
• Advise patients to maintain a consistent vitamin K intake when taking warfarin and to avoid sudden changes in their consumption of vitamin K-rich foods like leafy greens
• Suggest alternative food choices or cooking methods to minimize drug-nutrient interactions
  • Patients on statins can obtain CoQ10 from food sources like fatty fish, organ meats, and whole grains instead of supplements
• Collaborate with healthcare providers to adjust medication timing, formulation, or dose to optimize nutrient absorption and minimize interactions
  • Taking levothyroxine on an empty stomach and separating it from calcium and iron supplements can improve its absorption
• Provide patient education on reading food and supplement labels to identify potential interactions and make informed choices

Special Populations and Considerations

• Pregnant and lactating women may be more susceptible to drug-nutrient interactions due to changes in drug metabolism and increased nutrient requirements
  • Tetracycline antibiotics can cause tooth discoloration and bone growth inhibition in the developing fetus and should be avoided during pregnancy
• Older adults are at higher risk for drug-nutrient interactions due to age-related changes in drug metabolism, multiple medications, and altered nutrient absorption
  • Proton pump inhibitors can increase the risk of vitamin B12 deficiency in older adults, which may contribute to cognitive decline and neuropathy
• Critically ill patients may have impaired drug absorption and increased nutrient requirements, necessitating careful monitoring and individualized nutrition support
  • Enteral nutrition formulas can interact with medications, affecting their bioavailability and efficacy
• Patients with malabsorption disorders like celiac disease or inflammatory bowel disease may have altered drug absorption and nutrient deficiencies that require specialized management
• Vegetarians and vegans may be at risk for certain nutrient deficiencies that can interact with medications, such as iron deficiency anemia affecting the response to erythropoiesis-stimulating agents
• Patients with genetic variations in drug-metabolizing enzymes or transport proteins may have unique drug-nutrient interaction profiles that require personalized recommendations
  • Individuals with MTHFR polymorphisms may have impaired folate metabolism and require higher doses of folate supplements when taking methotrexate

Clinical Applications and Case Studies

• Case 1: A 65-year-old woman taking warfarin for atrial fibrillation experiences an elevated INR after increasing her intake of spinach and kale. The registered dietitian recommends maintaining a consistent vitamin K intake and provides education on low-vitamin K food choices.
• Case 2: A 50-year-old man with type 2 diabetes and peripheral neuropathy is found to have low vitamin B12 levels due to long-term metformin use. The registered dietitian collaborates with the physician to start vitamin B12 supplementation and provides guidance on B12-rich food sources.
• Case 3: A 30-year-old pregnant woman with a history of urinary tract infections is prescribed nitrofurantoin. The registered dietitian educates her on the importance of taking the medication with food to enhance its absorption and minimize gastrointestinal side effects.
• Case 4: A 75-year-old man taking a calcium channel blocker for hypertension experiences constipation and reduced appetite. The registered dietitian recommends increasing his intake of high-fiber foods and spacing his medication apart from meals to minimize the impact on nutrient absorption.
• Case 5: A 40-year-old woman with rheumatoid arthritis is prescribed methotrexate and expresses concern about its potential impact on her nutrient status. The registered dietitian provides education on the importance of folate supplementation and recommends a balanced diet rich in fruits, vegetables, and whole grains to support overall nutrient intake.
• Case 6: A 55-year-old man with hyperlipidemia is started on a statin medication and reports muscle pain and weakness. The registered dietitian assesses his diet and recommends increasing his intake of CoQ10-rich foods like fatty fish and whole grains to help mitigate statin-induced CoQ10 depletion.
• Case 7: A 28-year-old vegetarian woman with iron deficiency anemia is prescribed oral iron supplements. The registered dietitian provides guidance on taking the supplements with vitamin C-rich foods to enhance iron absorption and spacing them apart from calcium-rich meals and beverages to minimize interactions.