If you are starting a new medication, you're probably wondering if you should take it with or without food. The presence of food may affect the absorption of your medication. Some foods are known to slow drug absorption, increasing the amount of time it takes for the drug to work.
Drug Absorption and Bioavailability
Most drugs are taken by mouth. In this case, they pass through your stomach and liver before they reach the small intestine for absorption into your bloodstream. Drugs taken orally are not 100 percent bioavailable. Bioavailability refers to the amount of the active drug ingredient that makes it to your general circulation, and ultimately, to the site of action.
Delayed Drug Absorption
Drug absorption occurs in the early portion of your small intestine, where the extensive surface area allows for maximum absorption into your bloodstream. The presence of food and nutrients in the gastrointestinal tract slows down drug absorption. Prolonged absorption time is generally not an issue, as it does not affect the amount of drug absorbed. If you are taking medications that may be delayed by food, be consistent. Routinely take them either on an empty stomach or with food.
Drugs Delayed by Food
Some medications are known to exhibit delayed absorption in the presence of food and nutrients. A low fat meal slows down the absorption of nifedipine, an anti-hypertensive drug. A common side effect of nifedipine is flushing of the skin. Taking this drug with food reduces the side effect, but does not affect its efficacy. Other medications with delayed absorption from food include acetaminophen, aspirin, furosemide and phenytoin.
Foods that Delay Drug Absorption
Certain types of fiber affect medication absorption. Guar gum, a fermentable fiber used as a thickener in food products, slows the absorption of the oral diabetic drugs metformin and glyburide. The citrus peel fiber, pectin, may decrease absorption of cholesterol-lowering lovastatin. Take fiber supplements and high fiber meals at least 1 hour away from medications to avoid an interaction. Fatty foods, such as butter and full-fat dairy products, slow gastric emptying and thus drug absorption. Some drugs must be taken on an empty stomach.
Foods and nutrients can affect the way your body deals with medications in ways that are more significant than delaying absorption. Calcium and other minerals may bind to drugs, decreasing their effectiveness. Protein may compete with some drugs for absorption. Acidic foods and beverages, such as tomatoes or orange juice, may destroy some medications, or dissolve them prematurely. Alcohol slows the metabolism of some drugs, allowing them to build up to toxic levels in your body. Always read the label before taking your medication, and consult your doctor or pharmacist if you have questions.
- "Drug Nutrient Interactions and Herbal Use"; P. Burke, M. Roche-Dudek, K. Roche-Klemma; 2002
- Linus Pauling Institute Micronutrient Information Center; Fiber; V. Drake; August 2009
- The Merck Manual; Drug Absorption; K. Kopacek; November 2007
- Oklahoma State University; Oklahoma Cooperative Extension Service; Drug-Nutrient Interactions; J. Hermann