There are few things more uncomfortable than a gastrointestinal issue, whether it's nausea, diarrhea, or an ulcer. Thankfully, there are a variety of medications designed to treat these problems.

Anticholinergics

Anticholinergic medications -- for example, dicyclomine -- slow the action of the bowel and reduce the amount of stomach acid. Because these medications slow the action of the bowel by relaxing the muscles and relieving spasms, they are said to have an antispasmodic action.

Antidiarrheals

Diarrhea may be caused by many conditions, including influenza (the flu) and ulcerative colitis, and it can sometimes occur as a side effect of a medication. Narcotic drugs and anticholinergic medications slow the action of the bowel and can thereby help alleviate diarrhea. An antidiarrheal medication such as diphenoxylate and atropine combination contains both a narcotic and an anticholinergic.

Antiemetics

Antiemetic medications reduce the urge to vomit. One of the most effective of these medications is the phenothiazine derivative prochlorperazine. This medication acts on the vomiting center in the brain. It is often administered rectally and usually alleviates nausea and vomiting within a few minutes to an hour.

Other drugs that are used to combat nausea and vomiting include dolasetron, granisetron, and ondansetron. Antihistamines are also often used to prevent nausea and vomiting, especially when these problems are caused by motion sickness. This type of medication may also work on the vomiting center in the brain.

Antiulcer Medications

Antiulcer medications are prescribed to relieve the symptoms and promote the healing of peptic ulcers as well as to treat acid-reflux disease, which can cause severe heartburn pain in some people. Histamine (H-2) blockers, including cimetidine, famotidine, nizatidine, and ranitidine, work by preventing histamine from attaching to receptors on acid-secreting cells, thus keeping the histamine from triggering the secretion of stomach acid.

Another group of antiulcer drugs are the proton pump inhibitors (PPIs); they limit stomach-acid secretion by shutting down the acid pumps in the acid-secreting cells themselves. PPIs, which include omeprazole, pantoprazole, and lansoprazole, are commonly prescribed to treat and prevent many stomach problems. Another antiulcer drug, sucralfate, works by forming a chemical barrier over an exposed ulcer that protects the ulcer from stomach acid, much as a bandage protects a wound from debris. These medications provide sustained relief from ulcer and heartburn pain and promote healing.