McKenna's Pharmacology for Nursing, 2e

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

The evidence

BOX 57.2

Drugs that decrease acid may affect more than acid levels In December 2005, the Journal of the American Medical Association published a study that followed people taking proton pump inhibitors (Nexium and others) over a period of 10 years.The report showed that people using these drugs had Clostridium difficile infections leading to diarrhoea at three times the rate of people not using these drugs.There was also a reported two-time increase in these infections in people using histamine-2 (H 2 ) antagonists (cimetidine). C. difficile is a significant cause of diarrhoea in the community. Other studies have reported similar findings. Drugs that lower acid levels change the normal environment of the GI tract, perhaps allowing bacteria to thrive that would normally be destroyed by the acid. Most of these acid-lowering drugs are available in over-the-counter (OTC) preparations and may be used in excessive doses for prolonged periods of time without the healthcare provider’s knowledge.This information should alert healthcare providers and people to the need for caution in using these drugs. If a person is complaining about diarrhoea, the healthcare provider should specifically ask about the use of acid-lowering products (sometimes people do not even think of these products as drugs because they can buy them without a prescription). During healthcare teaching sessions, it is important to remind people to read the labels of OTC drugs carefully and to follow instructions. If a person feels the need to take one of these products for a prolonged

period of time, they should be advised to obtain a medical evaluation because the symptoms being treated with these drugs could have an underlying medical cause that should be evaluated. When evaluating the data from the study, the researchers also noted a similar increase in these GI infections in people using non-steroidal anti-inflammatory drugs (ibuprofen, ketoprofen and others) for a prolonged period of time.The researchers suggested that further study be done on that group of people to verify the finding. It is important to keep current with long-term studies on drugs and to remember that changing a normal function or environment in the body will change the balance of homeostasis in the body and could potentially cause other problems. In 2007, similar studies reported an increase in osteoporosis and bone fractures in people on long-term proton pump inhibitor use. Changing the acidity of the GI tract seems to affect calcium absorption. Further studies may show other changes in homeostasis with long-term use of these drugs. Dial, S., Delaney, J. A., Barkun, A. N. & Suissa, S. (2005). Use of gastric acid suppressive agents and the risk of community acquired Clostridium difficile associated diarrhoea. JAMA, 294, 2898–2995. Yu-Xiao,Y., Lewis, S. D, Epstein, S. & Metz, D. (2007). Long term proton pump inhibitor therapy and risk of hip fracture. JAMA, 296, 2947–2953.

Proton pump inhibitors work here: esomeprazole lansoprazole omeprazole pantoprazole rabeprazole

H 2

receptor sites

Parietal cells

Prostaglandin works here: misoprostol

Pancreatic enzyme works here: pancrelipase

Antacids work here: aluminium and calcium salts, magnesium salts, sodium bicarbonate

Antipeptic agent works here: sucralfate

FIGURE 57.1  Sites of action of drugs affecting gastrointestinal secretions.