McKenna's Pharmacology for Nursing, 2e

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Drugs affecting gastrointestinal motility

Learning objectives Upon completion of this chapter, you should be able to: 1. Describe the underlying processes in diarrhoea and constipation and correlate them with the types of drugs used to treat these conditions. 2. Describe the therapeutic actions, indications, pharmacokinetics, contraindications and cautions, most common adverse reactions and important drug–drug interactions associated with laxatives and antidiarrhoeal drugs. 3. Discuss the use of laxatives and antidiarrhoeal agents across the lifespan. 4. Compare and contrast the prototype laxatives and antidiarrhoeals with other agents in their class and with other classes of laxatives and antidiarrhoeals. 5. Outline the care considerations, including important teaching points, for people receiving laxatives and antidiarrhoeal agents.

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Glossary of key terms antidiarrhoeal drug: drug that blocks the stimulation of the gastrointestinal (GI) tract, leading to decreased activity and increased time for absorption of needed nutrients and water bulk stimulant: agent that increases in bulk, frequently by osmotic pull of fluid into the faeces; the increased bulk stretches the GI wall, causing stimulation and increased GI movement cathartic dependence: overuse of laxatives that can lead to the need for strong stimuli to initiate movement in the intestines; local reflexes become resistant to normal stimuli after prolonged use of harsher stimulants, leading to further laxative use chemical stimulant: agent that stimulates the normal GI reflexes by chemically irritating the lining of the GI wall, leading to increased activity in the GI tract constipation: slower-than-normal evacuation of the large intestine, which can result in increased water absorption from the faeces and can lead to impaction diarrhoea: more-frequent-than-normal bowel movements, often characterised as fluid-like and watery because not enough time for absorption is allowed during the passage of food through the intestines lubricant: agent that increases the viscosity of the faeces, making it difficult to absorb water from the bolus and easing movement of the bolus through the intestines

LAXATIVES Chemical stimulants bisacodyl senna Bulk stimulants

ANTIDIARRHOEALS bovine colostrum loperamide opium derivatives Ulcerative colitis drugs

IRRITABLE BOWEL SYNDROME DRUGS hyoscine mebeverine peppermint oil

Lubricants docusate glycerol

liquid paraffin Other laxatives methylnaltrexone

lactulose psyllium

balsalazide mesalazine olsalazine

sodium chloride-sodium bicarbonate-potassium chloride solution