McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 5 8 Drugs affecting gastrointestinal motility

ANTIDIARRHOEALS Antidiarrhoeals block stimulation of the GI tract for symptomatic relief from diarrhoea. Available agents include loperamide ( Imodium ), kaolin, codeine and opium derivatives. Several antidiarrhoeal products are available in combination (Box 58.3). Other anti­ diarrhoeals are salicylate derivatives that are used to reduce inflammation and associated diarrhoea in

individuals with inflammatory bowel disease, such as ulcerative colitis. These include balsalazide ( Colazide ), mesalazine ( Pentasa, Mesasal, Salofalk and others) and olsalazine ( Dipentum ). There is also a drug approved strictly for use in pre- venting traveller’s diarrhoea (Box 58.4). Therapeutic actions and indications Antidiarrhoeal agents slow the motility of the GI tract through direct action on the muscles of the GI tract to slow activity (loperamide) or through action on CNS centres that cause GI spasm and slowing (opium derivatives; see Figure 58.1). These drugs are indicated for the relief of symptoms of acute and chronic diarrhoea, reduction of volume of discharge from ileostomies and prevention and treatment of traveller’s diarrhoea (Table 58.2; Box 58.4). Bovine colostrum ( Travelan ) has been found to be very helpful in treating traveller’s diarrhoea ( see the Critical thinking scenario for additional information ). Pharmacokinetics Loperamide is slowly absorbed after oral administra- tion, metabolised in the liver and excreted in urine and faeces. It may cross the placenta and enter breast milk. Codeine, a controlled substance, is readily absorbed after oral administration, metabolised in the liver and excreted in urine. It crosses the placenta and enters breast milk. Salicylates are readily absorbed directly from the stomach, reaching peak levels within 5 to 30 minutes. They are metabolised in the liver to salicylic acid, an active metabolite and excreted in the urine, with a half-life of 15 minutes to 12 hours, depending on the salicylate. Salicylates cross the placenta and enter breast milk; they are not indicated for use during pregnancy or breastfeeding because of the potential adverse effects on the neonate and associated bleeding risks for the mother.

■■ BOX 58.3  Combination antidiarrhoeal products

Some popular antidiarrhoeal agents combine different compounds.

codeine, kaolin, aluminium hydroxide, pectin ( Bis-Pectin ) diphenoxylate with atropine ( Lofenoxal, Lomotil )

Adult and paediatric (>12 years): 15 mL hourly for three doses, then q 3 hours Paediatric (8–11 years): 11 mL q 4 hours Adult: 5 mg PO t.d.s. or q.i.d. initially, reducing when controlled

■■ BOX 58.4  Treating traveller’s diarrhoea

Recently, bovine colostrum ( Travelan ) has been approved for use in prevention of traveller’s diarrhoea. The preparation contains high levels of antibodies against E. coli to prevent infections caused by the bacteria, a common cause of traveller’s diarrhoea. Other available products work to manage diarrhoea from E. coli infection once it has occurred. One capsule is taken before each meal, and additional capsules can be taken if needed in between meals when there may be increased risk of infection.

TABLE 58.2

DRUGS IN FOCUS Antidiarrhoeals

Drug name

Dosage/route

Usual indications

bovine colostrum (Travelan)

200 mg PO t.d.s. on empty stomach at least 1 hour before food and 2 hours after Adult: 4 mg PO, then 2 mg PO after each loose stool

Management of traveller’s diarrhoea

Short-term treatment of diarrhoea associated with dietary problems, viral infections

loperamide (Imodium)

Ulcerative colitis drugs balsalazide (Colazide)

Three 750-mg capsules PO t.d.s. for 8 weeks

Treatment of mildly to moderately acute ulcerative colitis in adults Treatment of ulcerative colitis and other inflammatory bowel disease in adults

mesalazine (Pentasa, Mesasal, Salofalk, others) olsalazine (Dipentum)

500 mg PO t.d.s.; one enema at bedtime or one suppository once daily

1 g/day PO in two divided doses

Treatment of ulcerative colitis and other inflammatory bowel disease in adults