McKenna's Pharmacology for Nursing, 2e

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P A R T 1 1  Drugs acting on the gastrointestinal system

TABLE 58.1

DRUGS IN FOCUS Laxatives

Drug name

Dosage/route

Usual indications

Chemical stimulants bisacodyl (Bisalax, Dulcolax)

10–15 mg PO at night, or one suppository PR at night

Emptying of the gastrointestinal (GI) tract before some surgeries or diagnostic tests (e.g. barium enema); prevention of constipation and straining after GI surgery, myocardial infarction (MI), obstetrical delivery; short-term treatment of constipation Short-term treatment of constipation; treatment of encopresis; found in many over-the-counter (OTC) preparations Short-term treatment of constipation; alternative choice for people with cardiovascular disorders Mild laxative; short-term treatment of constipation Stimulates bowel evacuation prior to GI examination (e.g. colonoscopy, sigmoidoscopy)

senna (Senokot)

Two to four tablets PO per day at bedtime or 1–2 teaspoons of granules PO per day at bedtime

Bulk stimulants lactulose (Actilax, Chronulac)

15–30 mL PO

psyllium (Metamucil)

1 tsp or packet in cold water, one to three times per day; ½ packet for children Dosage: 2–4 L of oral solution on empty stomach in the evening prior to procedure

sodium chloride-sodium bicarbonate-potassium chloride solution (ColonLYTELY )

Lubricants docusate (Coloxyl, Sennesoft)

100–240 mg PO

Prophylaxis for people who should not strain (such as after surgery, myocardial infarction or obstetrical delivery) Short-term treatment of constipation

glycerol (generic)

One suppository PR. Allow to remain for 15–30 mins Adults and Paediatric (>6 years): 15–30 mL at bedtime Paediatric (3–6 years): 10–15 mL at bedtime

Short-term treatment of constipation

liquid paraffin (Agarol)

L ubricants Sometimes it is desirable to make defecation easier without stimulating the movement of the GI tract. This is done using lubricants . People with haemorrhoids and those who have recently had rectal surgery may need lubrication of the stool. Some people who could be harmed by straining might also benefit from this type of laxative. The type of laxative recommended depends on the condition of the person, the speed of relief needed and the possible implication of various adverse effects. Lubricating laxatives include docusate ( Coloxyl ), glycerol (generic) and liquid paraffin ( Agarol ). Therapeutic actions and indications Docusate has a detergent action on the surface of the intestinal bolus, increasing the admixture of fat and water and making a softer stool. Glycerol is a hyperosmolar laxative that is used in suppository form to gently evacuate the rectum without systemic effects higher in the GI tract.

Liquid paraffin is the oldest of these laxatives. It is not absorbed and forms a slippery coat on the contents of the intestinal tract. When the intestinal bolus is coated with liquid paraffin, less water is absorbed out of the bolus, and the bolus is less likely to become hard or impacted. Pharmacokinetics These drugs are not absorbed systemically and are excreted in the faeces. Docusate and liquid paraffin are given orally. Glycerol is available as a rectal suppository. Contraindications and cautions These laxatives are contraindicated with allergy to any component of the drug to prevent hypersensitivity reactions ; and in acute abdominal disorders, including appendicitis, diverticulitis and ulcerative colitis, when increased motility could lead to rupture or further exacerbation of the inflammation. Laxatives should be used with caution in heart block, CAD and debilitation, which could be affected by the decrease in absorption