Diarrhea, drugs used opioids

The answer is e. (Hardmanr p 926.) Diphenoxylate is a piperidine opioid that is related to meperidine, it inhibits peristalsis and, hence, increases the passage time of the intestinal bolus. Lt is combined with atropine to discourage use as a street drug. Atropine has little effect on peristalsis. Clonidine, bismuth subsalicylate, and re hydration therapy are all useful in some types of diarrhea, but none of them inhibit peristalsis. 

The continued use of opioids results in the development of physical dependence, as demonstrated by the appearance of a characteristic abstinence syndrome upon interruption or cessation of use. The symptoms of withdrawal include hyperactivity, anxiety, restlessness, yawning, diarrhea, vomiting, chills, fever, lacrimation, and runny nose. Piloerection (gooseflesh or cold turkey), mydriasis, increased blood pressure and heart rate, and hyperpyrexia may be observed. Tremors, abdominal cramps, and muscle and joint pain may be present. Drug craving is an important feature of opioid withdrawal. In contrast to some other drugs of abuse, withdrawal is not life threatening. 

Among the compounds that fall within this class are hydrocodone (e.g., Vicodin), oxycodone (e.g., OxyContin—an oral, controlled-release form of the drug), morphine, fentanyl, codeine, and related medications. Morphine and fentanyl are often used to alleviate severe pain, while codeine is used for milder pain. Other examples of opioids prescribed to relieve pain include propoxyphene (Darvon) hydromorphone (Dilaudid) and meperidine (Demerol), which is used less often because of its side effects. In addition to their effective pain-relieving properties, some of these medications can be used to relieve severe diarrhea (for example, Lomotil, also known as diphenoxylate) or severe coughs (codeine). 

The primary side effects with these drugs are nausea, abdominal discomfort, constipation, and other GI disturbances. Drowsiness, fatigue, and dizziness have also been reported. Although addiction is a potential problem when opioids are administered, the risk of tolerance and physical dependence is fairly small when these drugs are used in recommended dosages for the short-term treatment of diarrhea. 

Two drugs widely used to control diarrhea are diphenoxylate [di PHEN ox a late and loperamide [loe PER a mide]. Both are analogues of meperidine (see p. 138) and have opioid-like actions on the gut, activating presynaptic opioid receptors in the enteric nervous system to inhibit acetylcholine release and decrease peristalsis. Side effects include drowsiness, abdominal cramps and dizziness. Since these drugs can cause toxic megacolon, they should not be used in young children or patients with severe colitis. 

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