Adverse effects of drugs on the gastrointestinal (GI) system are especially important because of their frequency and their potential to cause negative nutritional consequences. One study concluded that 20-40 percent of drug-induced adverse effects are associated with the GI tract. Healthcare providers should be aware of the drugs commonly associated with GI adverse effects and patients need to be alerted of early symptoms of GI disorders so that they can seek care that can prevent long-term complications.
Side effects such as nausea, vomiting, dyspepsia (indigestion), abdominal cramps, diarrhea, and constipation are usually transient and resolve soon after the medication is discontinued. But more serious and persistent adverse effects, such as stricture (narrowing of a portion of the GI tract), mucosal ulceration, and increased susceptibility to pseudomembranous colitis, can be caused by certain widely prescribed drugs. The elderly are particularly susceptible to drug-induced GI effects. In some cases, the side effects are worse than the condition for which the drug was prescribed.
The following outlines of some common drug-induced GI effects:
Oral cavity
- Taste disturbance/disorder – in addition to decreasing nutritional and caloric intake, taste disorders can affect digestion by altering salivary and pancreatic flow, gastric contraction, and intestinal peristalsis
- Xerostomia (dry mouth) – can affect nutritional status by making it difficult to chew, taste (ageusia), and swallow food (dysphagia). Can also make it difficult to speak (dysphonia)
- Oral lesions – erythema multiforme, for example
- Gingival enlargement (overgrowth of the periodontal tissue)
Esophagus
- Irritation (esophagitis)
- Gastroesophageal Reflux Disease (GERD)
Stomach and duodenum
- Nausea and vomiting
- Delayed gastric emptying – drugs with an anticholinergic effect and some drugs prescribed to treat depression and Parkinson’s disease can cause the stomach to empty its contents into the duodenum at a slower rate than normal
- NSAID-induced gastroduodenal mucosal injury – the widespread use of NSAIDs make this often misdiagnosed problem a serious one
- Hypochlorhydra (abnormally low production of stomach acid)
Small intestine
- Ulcers – the primary culprits are potassium supplements and NSAIDs
- Hemorrhage – can be caused by anticoagulants, usually in those with preexisting intestinal lesions
- Malabsorption – drugs can interfere with the absorption of specific nutrients
- Dysmotility – while drugs are likelier to affect the motor activity of the colon, certain drugs can also inhibit the motility of the small intestine
- Cytotoxic (chemotherapy) effects on the intestinal mucosal cells
Large intestine
- Cathartic colon – occurs with the chronic use of stimulant laxatives
- Diarrhea
- Pseudomembranous colitis – bacterial infection of the colon with potentially serious consequences
- NSAID-induced colitis – NSAIDs can cause colitis or exacerbate a pre-existing colonic disease
- Irritable Bowel Syndrome (IBS) / Inflammable Bowel Disease (IBD)