McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 5 7 Drugs affecting gastrointestinal secretions

of erosive oesophagitis and ulcers; and in combination with amoxycillin and clarithromycin for the treatment of H. pylori infection. See Table 57.1 for usual indica- tions for each of these agents. Pharmacokinetics Esomeprazole, omeprazole and pantoprazole are availa- ble in oral forms and as IV preparations. Lansoprazole and rabeprazole are available only in delayed-release oral forms. These drugs are acid labile and are rapidly absorbed from the GI tract, reaching peak levels in 3 to 5 hours. They undergo extensive metabolism in the liver and are excreted in urine. Omeprazole is faster acting and more quickly excreted than the other proton pump inhibitors. It has a half-life of 30 to 60 minutes. Esomeprazole is a longer-acting drug; it has a half-life of 60 to 90 minutes and a duration of 17 hours. It is not broken down as rapidly in the liver as the parent drug omeprazole. Lan- soprazole has a half-life of 2 hours and duration of 12 hours. Pantoprazole and rabeprazole have half-lives of 90 minutes and durations of 12 to 14 hours. There are no adequate studies about whether these drugs cross the placenta or enter breast milk. Contraindications and cautions These drugs are contraindicated in the presence of known allergy to either the drug or the drug compo- nents to prevent hypersensitivity reactions . Caution should be used in pregnant or breastfeeding women because of the potential for adverse effects on the fetus or neonate . The safety and efficacy of these drugs have not been established for people younger than 18 years of age, except for lansoprazole, which is the proton pump inhibitor of choice if one is needed for a child. Monitoring of serum magnesium levels prior to and during treatment should be considered for: • people expected to require long-term PPI treatment. • people who take other medicines such as digoxin or medicines that may cause hypomagnesaemia (such as diuretics). Adverse effects The adverse effects associated with these drugs are related to their effects on the H + , K + -ATPase pump on the parietal and other cells. CNS effects of dizziness and headache are commonly seen; asthenia (loss of strength), vertigo, insomnia, apathy and dream abnormalities may also be observed. GI effects can include diar- rhoea, abdominal pain, nausea, vomiting, dry mouth and tongue atrophy. Upper respiratory tract symptoms, including cough, stuffy nose, hoarseness and epistaxis, are frequently seen. Other, less common adverse effects

include rash, alopecia, pruritus, dry skin, back pain and fever. In preclinical studies, long-term effects of proton pump inhibitors included the development of gastric cancer. Recent studies show an increase in bone loss in people using these drugs long term. Clinically important drug–drug interactions There is a risk of increased serum levels and increased toxicity of benzodiazepines, phenytoin and warfarin if these are combined with these drugs; people should be monitored closely. Decreased levels of ketoconazole and theophylline have been reported when combined with these drugs, leading to loss of effectiveness. Sucralfate is not absorbed well in the presence of these drugs, and doses should be spaced at least 30 minutes apart if this combination is used. heartburn or symptoms of gastro-oesophageal reflux; treatment of pathological hypersecretory syndromes; eradication of H. pylori infection as part of combination therapy. Actions: Specifically inhibits the hydrogen– potassium adenosine triphosphatase enzyme system on the secretory surface of the gastric parietal cells, blocking the final step in acid production and decreasing gastric acid levels. Pharmacokinetics: Route Onset Peak Duration Oral Varies 0.5–3.5 hours Varies T 1/2 : 30 to 60 min; metabolised in the liver and excreted in urine and bile. Adverse effects: Headache, dizziness, vertigo, insomnia, rash, diarrhoea, abdominal pain, nausea, vomiting, upper respiratory infection symptoms, cough. Prototype summary: Omeprazole Indications: Short-term treatment of active duodenal ulcer or active benign gastric ulcer; treatment of

Care considerations for people receiving proton pump inhibitors

Assessment: History and examination

■ ■ Assess for possible contraindications or cautions : history of allergy to a proton pump inhibitor to reduce the risk of hypersensitivity reaction ; current status of pregnancy or breastfeeding because of the potential for adverse effects on the fetus or infant . ■ ■ Perform a physical examination to establish baseline data before beginning therapy