Nutrition can affect the body’s response to medications; conversely, medications can affect the body’s nutrition.
Foods can enhance, delay, or decrease drug absorption. Foods impair absorption of many antibiotics. They can alter metabolism of drugs; eg, high-protein diets can accelerate metabolism of certain drugs by stimulating cytochrome P-450. Eating grapefruit can inhibit cytochrome P-450 34A, slowing metabolism of some medications (eg, amiodarone, carbamazepine, cyclosporine, certain calcium channel blockers, statins). Diets that alter the bacterial flora may markedly affect the overall metabolism of certain medications.Foods can enhance, delay, or decrease drug absorption. Foods impair absorption of many antibiotics. They can alter metabolism of drugs; eg, high-protein diets can accelerate metabolism of certain drugs by stimulating cytochrome P-450. Eating grapefruit can inhibit cytochrome P-450 34A, slowing metabolism of some medications (eg, amiodarone, carbamazepine, cyclosporine, certain calcium channel blockers, statins). Diets that alter the bacterial flora may markedly affect the overall metabolism of certain medications.
Some foods affect the body’s response to medications. For example, tyramine, a component of cheese and a potent vasoconstrictor, can cause hypertensive crisis in some patients who take monoamine oxidase inhibitors and eat cheese.
Nutritional deficiencies can affect drug absorption and metabolism. Severe energy and protein deficiencies reduce tissue enzyme concentrations and may impair the response to medications by reducing absorption or protein binding and causing liver dysfunction. Changes in the gastrointestinal tract can impair absorption and affect the response to a medication. Deficiency of calcium, magnesium, or zinc may impair drug metabolism. Vitamin C deficiency decreases activity of drug-metabolizing enzymes, especially in older adults.
Many medications affect appetite, food absorption, and tissue metabolism (see table Effects of Some Medications). Some medications (eg, metoclopramide) increase gastrointestinal motility, decreasing food absorption. Other medications (eg, opioids, anticholinergics) decrease gastrointestinal motility. Some medications are better tolerated if taken with food.). Some medications (eg, metoclopramide) increase gastrointestinal motility, decreasing food absorption. Other medications (eg, opioids, anticholinergics) decrease gastrointestinal motility. Some medications are better tolerated if taken with food.
Effects of Some Medications and Substances on Appetite, Food Absorption, and Metabolism
Medications and Substances | Effect |
|---|---|
Alcohol, antihistamines, glucocorticoids, dronabinol, insulin, megestrol acetate, mirtazapine, many psychoactive drugs, sulfonylureas, thyroid hormoneAlcohol, antihistamines, glucocorticoids, dronabinol, insulin, megestrol acetate, mirtazapine, many psychoactive drugs, sulfonylureas, thyroid hormone | Increases appetite |
Some antibiotics, bulk agents (methylcellulose, guar gum), cyclophosphamide, digoxin, glucagon, indomethacin, morphine, fluoxetineSome antibiotics, bulk agents (methylcellulose, guar gum), cyclophosphamide, digoxin, glucagon, indomethacin, morphine, fluoxetine | Decreases appetite |
OrlistatOrlistat | Decreases absorption of fats |
Octreotide, opioids, phenothiazines, second-generation antipsychotics, phenytoin, probenecid, thiazide diuretics, corticosteroids, warfarin Octreotide, opioids, phenothiazines, second-generation antipsychotics, phenytoin, probenecid, thiazide diuretics, corticosteroids, warfarin | Increases blood glucose levels |
Angiotensin-converting enzyme (ACE) inhibitors, aspirin, barbiturates, beta-blockers, insulin, monoamine oxidase inhibitors (MAOIs), oral antihyperglycemic drugs, phenacetin, phenylbutazone, sulfonamides Angiotensin-converting enzyme (ACE) inhibitors, aspirin, barbiturates, beta-blockers, insulin, monoamine oxidase inhibitors (MAOIs), oral antihyperglycemic drugs, phenacetin, phenylbutazone, sulfonamides | Decreases blood glucose levels |
Aspirin and Aspirin andp-aminosalicylic acid, L-asparaginase, chlortetracycline, colchicine, dextrans, glucagon, niacin, phenindione, statins, sulfinpyrazone, trifluperidol-aminosalicylic acid, L-asparaginase, chlortetracycline, colchicine, dextrans, glucagon, niacin, phenindione, statins, sulfinpyrazone, trifluperidol | Decreases blood lipid levels |
Adrenal corticosteroids, chlorpromazine, some second-generation antipsychotics, ethanol, growth hormone, oral contraceptives (estrogen-progestin type), thiouracil, vitamin DAdrenal corticosteroids, chlorpromazine, some second-generation antipsychotics, ethanol, growth hormone, oral contraceptives (estrogen-progestin type), thiouracil, vitamin D | Increases blood lipid levels |
Chloramphenicol, tetracyclineChloramphenicol, tetracycline | Decreases protein metabolism |
Certain medications and substances affect mineral metabolism (see table Possible Effects of Medications on Mineral Metabolism). Certain antibiotics (eg, tetracyclines) reduce iron absorption, as can certain foods (eg, vegetables, tea, bran).
Possible Effects of Medications on Mineral Metabolism
Medications | Effects |
|---|---|
Diuretics, especially thiazides, and corticosteroids | Can deplete body potassium* |
Laxatives if used repeatedly | May deplete potassium* |
Cortisol, desoxycorticosterone, and aldosterone† | Cause marked sodium and water retention, at least temporarily |
Sulfonylureas and lithiumSulfonylureas and lithium | Impair uptake or release of iodine by the thyroid |
Oral contraceptives | Lower blood zinc levels, increase copper levelsLower blood zinc levels, increase copper levels |
Certain antibiotics (eg, tetracyclines) | Reduce iron absorption |
* Depletion of potassium increases susceptibility to digoxin-induced cardiac arrhythmias.* Depletion of potassium increases susceptibility to digoxin-induced cardiac arrhythmias. | |
† Retention of sodium and water is much less with prednisone, prednisolone, and some other corticosteroid analogs.† Retention of sodium and water is much less with prednisone, prednisolone, and some other corticosteroid analogs. | |
Certain medications affect vitamin absorption or metabolism (see table Possible Effects of Drugs on Vitamin Absorption or Metabolism).
Possible Effects of Medications on Vitamin Absorption or Metabolism
Medications | Effects |
|---|---|
Ethanol Ethanol | Impairs thiamin utilization |
Isoniazid Isoniazid | Interferes with niacin and pyridoxine metabolismand pyridoxine metabolism |
Ethanol and oral contraceptivesEthanol and oral contraceptives | Inhibit folate absorption |
Phenytoin, phenobarbital, primidone, or phenothiazines Phenytoin, phenobarbital, primidone, or phenothiazines | In most patients, cause folate (folic acid) deficiency*, probably because hepatic microsomal drug-metabolizing enzymes are affectedIn most patients, cause folate (folic acid) deficiency*, probably because hepatic microsomal drug-metabolizing enzymes are affected |
Antiseizure drugs (eg, carbamazepine, phenobarbital, phenytoin) Antiseizure drugs (eg, carbamazepine, phenobarbital, phenytoin) | Can decrease vitamin D metabolismCan decrease vitamin D metabolism |
Aminosalicylic acid, slow-release potassium iodide, colchicine, trifluoperazine, metformin, ethanol, and oral contraceptives Aminosalicylic acid, slow-release potassium iodide, colchicine, trifluoperazine, metformin, ethanol, and oral contraceptives | Interfere with absorption of vitamin B12 |
Proton pump inhibitors | Can decrease absorption of vitamin B12, vitamin C, iron, calcium, and magnesium |
* Folate supplements may make phenytoin less effective.* Folate supplements may make phenytoin less effective. | |
