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The EsophagusThe StomachThe IntestineThe LiverGlossary of Medicines Additional ReadingsAdditional Resources Many medicines taken by mouth may affect the digestive system.
These medicines include prescription (those ordered by a doctor anddispensed by a pharmacist) and nonprescription or over-the-counter(OTC) products. A glossary at the end of this fact sheet describessome common prescription and nonprescription medicines discussedbelow that may affect the digestive system.
Although these medicines usually are safe and effective, harmfuleffects may occur in some people. OTC's typically do not causeserious side effects when taken as directed on the product's label. Itis important to read the label to find out the ingredients, side effects,warnings, and when to consult a doctor.
Always talk with your doctorbefore taking a medicine for thefirst time and before adding anynew medicines to those youalready are taking. Tell the doctorabout all other medicines(prescription and OTC's) you aretaking. Certain medicines takentogether may interact and causeharmful side effects. In addition,tell the doctor about any allergiesor sensitivities to foods andmedicines and about any medicalconditions you may have such asdiabetes, kidney disease, or liverdisease.
Be sure that you understand alldirections for taking the medicine,including dose and schedule,possible interactions with food,alcohol, and other medicines, sideeffects, and warnings. If you arean older adult read all directionscarefully and ask your doctor questions about the medicine. As youget older, you may be more susceptible to drug interactions thatcause side effects.
People with a food intolerance such as gluten intolerance shouldmake sure their medicines do not contain fillers or additives withgluten. Check with your doctor if you have any questions orconcerns about your medicines. Follow the doctor's orders carefully,and immediately report any unusual symptoms or the warning signsdescribed below.
The Esophagus
Irritation
Some people have difficulty swallowing medicines in tablet orcapsule form. Tablets or capsules that stay in the esophagus mayrelease chemicals that irritate the lining of the esophagus. Theirritation may cause ulcers, bleeding, perforation (a hole or tear), andstrictures (narrowing) of the esophagus. The risk of pill-inducedinjuries to the esophagus increases in persons with conditionsinvolving the esophagus, such as strictures, scleroderma (hardeningof the skin), achalasia (irregular muscle activity of the esophagus,which delays the passage of food), and stroke.
Some medicines can cause ulcers when they become lodged in theesophagus. These medicines include aspirin, several antibiotics suchas tetracycline, quinidine, potassium chloride, vitamin C, and iron.
Warning signs
Pain when swallowing food or liquid. Feeling of a tablet or capsule "stuck" in the throat. Dull, aching pain in the chest or shoulder after takingmedicines. Precautions
Swallow tablets or capsules while you are in an upright orsitting position. Before taking a tablet or capsule, swallow several sips ofliquid to lubricate the throat, then swallow the tablet orcapsule with at least a full glass (8 ounces) of liquid. Do not lie down immediately after taking medicines to ensurethat the pills pass through the esophagus into the stomach. Tell your doctor if painful swallowing continues or if pillscontinue to stick in the throat. Esophageal Reflux
The lower esophageal sphincter (LES) muscle is between theesophagus and the stomach. The muscle allows the passage of foodinto the stomach after swallowing. Certain medicines interfere withthe action of the sphincter muscle, which increases the likelihood ofbackup or reflux of the highly acidic contents of the stomach intothe esophagus.
Medicines that can cause esophageal reflux include nitrates,theophylline, calcium channel blockers, anticholinergics, and birthcontrol pills.
Warning signs
Heartburn or indigestion. Sensation of food coming back up into the throat. Precautions
Avoid foods and beverages that may worsen reflux, includingcoffee, alcohol, chocolate, and fried or fatty foods. Cut down on, or preferably quit, smoking. Do not lie down immediately after eating. The Stomach
Irritation
One of the most common drug-induced injuries is irritation of thelining of the stomach caused by nonsteroidal anti-inflammatorydrugs (NSAIDs). NSAIDs can irritate the stomach by weakening the ability of thelining to resist acid made in the stomach. Sometimes this irritationmay lead to inflammation of the stomach lining (gastritis), ulcers,bleeding, or perforation of the lining.
In addition, you should be aware that stomach irritation may occurwithout having any of the symptoms below. Older people are especially at risk for irritation from NSAIDsbecause they are more likely to regularly take pain medicines forarthritis and other chronic conditions. Also at risk are individualswith a history of peptic ulcers and related complications or gastritis.
These individuals should tell their doctor about any of theseprevious conditions. Special medicines may be needed to protect thestomach lining.
Warning signs
Severe stomach cramps or pain or burning in the stomach orback. Black, tarry, or bloody stools. Bloody vomit. Severe heartburn or indigestion. Diarrhea. Precautions
Use coated tablets, which may lessen stomach irritation. Avoid drinking alcoholic beverages while taking medicines. Take medicines with a full glass of water or milk or with food,which may reduce irritation. Delayed Emptying of the Stomach
Some medicines cause nerve and muscle activity to slow down inthe stomach. This slowing down causes the contents of the stomachto empty at a slower rate than normal. Drugs that may cause this delay include anticholinergics and drugsused to treat Parkinson's disease and depression.
Warning signs
Nausea. Bloating. Feeling of fullness. Vomiting of food eaten many hours earlier. Pain in midabdomen. Heartburn or indigestion. Sensation of food coming back up into the throat. Precautions
Eat frequent, small meals. Do not lie down for about 30 minutes after eating. Tell your doctor if symptoms continue. Your doctor mayconsider changing your dosage of the medicine or trying anew medicine. The Intestine
Constipation
Constipation can be caused by a variety of medicines. Thesemedicines affect the nerve and muscle activity in the large intestine(colon). This results in the slow and difficult passage of stool.
Medicines also may bind intestinal liquid and make the stool hard.
Medicines that commonly cause constipation includeantihypertensives, anticholinergics, cholestyramine, iron, andantacids that contain mostly aluminium.
Warning sign
Constipation that is severe or disabling or that lasts severalweeks. Precautions
Drink plenty of fluids. Eat a well-balanced diet that includes whole grains, fruits, andvegetables. Exercise regularly. Take laxatives only under a doctor's supervision. Diarrhea
Diarrhea is a common side effect of many medicines. Diarrhea isoften caused by antibiotics, which affect the bacteria that livenormally in the large intestine.
Antibiotic-induced changes in intestinal bacteria allow overgrowthof another bacteria, Clostridium difficile (C. difficile), which is thecause of a more serious antibiotic-induced diarrhea. The presence of C. difficile can cause colitis, an inflammation of theintestine in which the bowel "weeps" excess water and mucus,resulting in loose, watery stools. Almost any antibiotic may cause C.
difficile-induced diarrhea, but the most common are ampicillin,clindamycin, and the cephalosporins. Antibiotic-induced colitis istreated with another antibiotic that acts on C. difficile. Diarrhea also can be a side effect of drugs that do not cause colitisbut that alter the movements or fluid content of the colon.
Colchicine is a common cause of drug-induced diarrhea.
Magnesium-containing antacids can have the effect of laxatives andcause diarrhea if overused. In addition, the abuse of laxatives mayresult in damage to the nerves and muscles of the colon and causediarrhea.
Warning signs
Blood, mucus, or pus in the stool. Pain in the lower abdomen. Fever. Precautions
If diarrhea lasts for several days, consult your doctor. The Liver
The liver processes most medicines that enter the bloodstream andgoverns drug activity throughout the body. Once a drug enters thebloodstream, the liver converts the drug into chemicals the body canuse and removes toxic chemicals that other organs cannot tolerate.
During this process, these chemicals can attack and injure the liver.
Drug-induced liver injury can resemble the symptoms of any acuteor chronic liver disease. The only way a doctor can diagnosedrug-induced liver injury is by stopping use of the suspected drugand excluding other liver diseases through diagnostic tests. Rarely,long-term use of a medicine can cause chronic liver damage andscarring (cirrhosis).
Medicines that can cause severe liver injury include large doses ofacetaminophen (and even in small doses when taken with alcohol),anticonvulsants such as phenytoin and valproic acid, theantihypertensive methyldopa, the tranquilizer chlorpromazine,antituberculins used to treat tuberculosis such as isoniazid andrifampin, and vitamins such as vitamin A and niacin.
Warning signs (for liver injury)
Severe fatigue. Abdominal pain and swelling. Jaundice (yellow eyes and skin, dark urine). Fever. Nausea or vomiting. Precautions
If you have ever had a liver disease or gallstones, you should
discuss this with your doctor before taking any medicines that
may affect the liver or the gallbladder.
Take these medicines only in the prescribed or recommended
doses.
Glossary of
The following glossary is a guide to medicines used to treat many Medicines
medical conditions. The glossary does not include all medicines thatmay affect the digestive system. If a medicine you are taking is notlisted here, check with your doctor.
Acetaminophen
Acetaminophen relieves fever and pain by blocking pain centers inthe central nervous system.
Examples of brand names include Tylenol, Panadol, and Datril.
Antacids
Antacids relieve heartburn, acid indigestion, sour stomach, andsymptoms of peptic ulcer. They work by neutralizing stomach acid. Aluminum hydroxide antacids include Alu-Tab and Amphojel;calcium carbonate antacids include Tums, Alka Mints, and RolaidsCalcium Rich; magnesium antacids include Mylanta and Maalox.
Antibiotics
Antibiotics destroy or block the growth of bacteria that causeinfection.
Hundreds of antibiotics are available, including penicillins (Amoxil,Amcil, and Augmentin), clindamycin, cephalosporins (Keflex andCeclor), tetracyclines (Minocin, Sumycin, and Vibramycin),quinolones (Cipro), and sulfa drugs (Bactrim). Anticholinergics
This class of medicines affects the nerve cells or nerve fibers andincludes drugs for depression, anxiety, and nervousness. Examples of anticholinergics include propantheline (Pro-banthine)and dicyclomine (Bentyl). Examples of antidepressants includeamitriptyline (Elavil and Endep), and nortriptyline (Aventyl andPamelor). Medicines for relieving the symptoms of Parkinson's disease also arein this category. Examples include levodopa (Dopar) and carbidopaand levodopa combination (Sinemet).
Anticonvulsants
These medicines control epilepsy and other types of seizuredisorders. They act by lessening overactive nerve impulses in thebrain. Examples of this class of medicines include phenytoin (Dilantin)and valproic acid (Dalpro).
Antihypertensives
Antihypertensives lower high blood pressure. They act by relaxingblood vessels, which makes blood flow more easily.
Examples of antihypertensives include methyldopa (Aldomet) andclonidine hydrochloride (Catapres).
Antituberculins
These drugs for tuberculosis limit the growth of bacteria or preventtuberculosis from developing in people who have a positivetuberculin skin test.
Brand names include INH, Dow-Isoniazid, Rifadin, and Rimactane.
Calcium channel blockers
These medicines for angina (chest pain) and high blood pressureaffect the movement of calcium into the cells of the heart and bloodvessels, relax blood vessels, and increase the flow of blood andoxygen to the heart. Examples of calcium channel blockers include diltiazem(Cardizem), nifedipine (Procardia), and verpamil (Isoptin).
Chlorpromazine
This tranquilizer relieves anxiety or agitation.
Examples of brand names include Thorazine and Ormazine.
Colchicine
This medicine eases the inflammation from gout and preventsattacks from recurring.
Iron is a mineral the body needs to produce red blood cells. Ironsupplements are used to treat iron deficiency or iron-deficiencyanemia.
Laxatives
Many forms of laxatives are available for relieving constipation. Common brand names of laxatives include Phillips' Milk ofMagnesia, Citroma, Epsom salts, Correctol, and ExLax. Nitrates
These drugs for angina (chest pain) relax blood vessels and increasethe flow of blood to the heart. Examples of generic and brand names include isosorbide dinitrate(Iso-Bid and Isonate) and nitroglycerin (Nitro-Bid and Nitrocap).
Nonsteroidal anti-inflammatory drugs (NSAIDs)
These drugs block the body's production of prostaglandins,substances that mediate pain and inflammation. NSAIDs relieve thepain from chronic and acute inflammatory conditions, includingarthritis and other rheumatic conditions, and pain associated withinjuries, bursitis, tendinitis, and dental problems. NSAIDs alsorelieve pain associated with noninflammatory conditions. Generic and brand names of NSAIDs include aspirin (Bayer andBufferin), ibuprofen (Advil, Nuprin, and Motrin), tometin(Tolectin), naproxen (Naprosyn), and piroxicam (Feldene).
Potassium chloride
Potassium is a vital element in the body. Potassium supplementshelp prevent and treat potassium deficiency in people takingdiuretics.
Quinidine
This medicine often is used to correct irregular heartbeat. Brand names of quinidine include Quinalan and Quiniglute.
Theophylline
This medicine eases breathing difficulties associated withemphysema, bronchitis, and bronchial asthma. The medicine worksby relaxing the muscles of the respiratory tract, which allows aneasier flow of air into the lungs. Examples of brand names include Theo-Dur, Theophyl, andBronkodyl.
Vitamins
Vitamins serve as nutritional supplements in people with poor diets,in people recovering from surgery, or in people with special healthproblems. Niacin helps the body break down food for energy and is used
to treat niacin deficiency and to lower levels of fats and
cholesterol.
Vitamin A is necessary for normal growth and for healthy
eyes and skin.
Vitamin C is necessary for healthy function of cells.
Additional
AARP Pharmacy Service Prescription Drug Handbook. Glenview, Readings
Illinois: Scott, Foreman and Company, 1988. General referencebook for the public by the American Association of Retired Personsthat provides information about medicines most frequentlyprescribed for persons over 50 years of age.
Advice for the Patient: Drug Information in Lay Language, USP DI,12th edition. Rockville, Maryland: The United States PharmacopeialConvention, 1992. Guide for the patient that provides informationabout medicines by brand and generic names in sections on dosageforms, proper use directions, precautions, and side effects.
Drug Information for the Health Care Professional, USP DI, 12thedition. Rockville, Maryland: The United States PharmacopeialConvention, 1992. Guide for health care professionals that providesinformation about medicines by brand and generic names in sectionson pharmacology, indications, precautions, side effects, generaldosing, dosage forms, and patient consultation.
Kimmey, MG. Gastroduodenal effects of nonsteroidalanti-inflammatory drugs. Postgraduate Medicine, 1989; 85(5):65-71. General review article for primary care physicians.
Physicians' Desk Reference, 46th edition. Montvale, New Jersey:Medical Economics Company, Inc., 1992. Reference book for healthcare professionals that includes information about 2,800pharmaceutical products in sections on pharmacology, indications,contraindications, precautions, adverse reactions, and dosage andadministration.
Stehlin, D. How to take your medicine: nonsteroidalanti-inflammatory drugs. FDA Consumer, 1990; 24(5): 33-35.
General review article for the public.
Additional
National Council on Patient Information and Education Resources
666 11th Street NW., Suite 810Washington, DC 20001(202) 347-6711 Distributes resources to the public and health care professionalsabout prescription medicines.
The United States Pharmacopeial Convention, Inc. 12601 Twinbrook ParkwayRockville, MD 20852 Distributes information about drug use and drug standards to healthprofessionals and the public.
The U.S. Government does not endorse or favor any specificcommercial product or company. Brand names appearing in thispublication are used only because they are considered essential inthe context of the information reported herein.
National Digestive Diseases Information
Clearinghouse
2 Information WayBethesda, MD 20892-3570E-mail: National Digestive Diseases InformationClearinghouse The National Digestive Diseases Information Clearinghouse(NDDIC) is a service of the National Institute of Diabetes andDigestive and Kidney Diseases (NIDDK). The NIDDK is part of theNational Institutes of Health under the U.S. Public Health Service.
Established in 1980, the clearinghouse provides information aboutdigestive diseases to people with digestive disorders and to theirfamilies, health care professionals, and the public. NDDIC answersinquiries; develops, reviews, and distributes publications; and worksclosely with professional and patient organizations and Governmentagencies to coordinate resources about digestive diseases.
Publications produced by the clearinghouse are reviewed carefullyfor scientific accuracy, content, and readability. This e-text is not copyrighted. The clearinghouse encourages usersof this e-pub to duplicate and distribute as many copies as desired.
NIH Publication No. 95-3421September 1992

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