31.3: Pepsin Inhibitors and Prostaglandin Analogues
By the end of this section, you should be able to:
- 31.3.1 Identify the characteristics of mucosal protectants and prostaglandin analogues used to treat gastrointestinal disorders.
- 31.3.2 Explain the indications, action, adverse reactions, and interactions of mucosal protectants and prostaglandin analogues used to treat gastrointestinal disorders.
- 31.3.3 Describe nursing implications of mucosal protectants and prostaglandin analogues used to treat gastrointestinal disorders.
- 31.3.4 Explain the client education related to mucosal protectants and prostaglandin analogues used to treat gastrointestinal disorders.
Mucosal Protectants
Pepsin is a gastric enzyme that breaks down and supports the digestion of proteins from foods. A low gastric pH of 1.5–2 activates pepsin. However, pepsin may cause erosive damage to the mucosal lining of the stomach. To mitigate the potential harm caused by pepsin, mucosal protectants are employed. These agents serve a dual purpose by reducing both gastric acid production and pepsin activity. Notably, when the gastric pH exceeds 5, mucosal protectants act as inhibitors of pepsin further safeguarding the delicate mucosal lining of the stomach.
Sucralfate
Sucralfate is classified as a mucosal protectant or coating agent. When ingested, it transforms into a viscous substance that adheres to ulcerated areas, creating a protective barrier on the mucosal lining of the stomach and duodenum. This protective paste-like barrier can adhere or stick to the ulcers for up to 6 hours, shielding them from the damaging effects of pepsin and hydrochloric acid. Sucralfate is especially effective with duodenal ulcers, ulcers due to aspirin use, and chemotherapy-induced mucositis. It may also be beneficial for stress ulcer prophylaxis.
Sucralfate is available in a tablet form or a liquid suspension. To maximize effectiveness, it should be taken 4 times a day, approximately 60 minutes before meals and at bedtime. When used alongside antacids in antiulcer therapy, it's advisable to administer antacids 30 minutes before or after sucralfate. Additionally, due to its adhesive properties, sucralfate should be taken at least 2 hours before or after medications such as quinolones, digoxin, phenytoin, and tetracycline to prevent any interference with their effectiveness.
Table 31.8 is a drug prototype table for sucralfate. It lists drug class, mechanism of action, adult dosage, indications, therapeutic effects, drug and food interactions, adverse effects, and contraindications.
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Drug Class
Mucosal protectant, coating agent Mechanism of Action Locally reacts with hydrochloric acid and pepsin in the stomach to form an adherent protective paste-like substance capable of acting as an acid buffer |
Drug Dosage
1 g orally 4 times daily for 4–8 weeks unless healing has been demonstrated by x-ray or endoscopic exam. |
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Indications
Short-term treatment of active duodenal ulcers Therapeutic Effects Protects damaged gastric mucosa from further damage caused by pepsin and hydrochloric acid |
Drug Interactions
Cimetidine Digoxin Fluroquinolones Ketoconazole Phenytoin Quinidine Ranitidine Tetracycline Theophylline Food Interactions No significant interactions Sucralfate should be taken on an empty stomach |
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Adverse Effects
Diarrhea Dry mouth Flatulence Nausea Pruritus Rash Dizziness Insomnia Headache Back pain Hyperglycemia |
Contraindications
Hypersensitivity Caution: Chronic kidney failure or dialysis secondary to risk of aluminum accumulation |
Prostaglandin Analogues
Prostaglandins are naturally occurring compounds present in the GI tract that protect the mucosal lining of the stomach and duodenum. They do this by inhibiting gastric acid and pepsin secretions.
Synthetic prostaglandin analogues, in a similar manner, act as mucosal protectants by decreasing acid secretions while increasing the secretion of bicarbonate and protective mucus. This combined action serves to fortify the defense mechanisms of the GI tract, preserving its delicate mucosal integrity.
Misoprostol
Misoprostol acts as an endogenous prostaglandin in the GI tract. As an antiulcer agent for the prevention of NSAID-induced ulcers, it inhibits basal and nocturnal gastric acid and pepsin secretions and also increases the secretion of bicarbonate and protective gastric mucous. Misoprostol also promotes vasodilation to maintain submucosal gastric blood flow. These actions prevent gastric ulcers.
Misoprostol is available in tablets that are administered with food 4 times a day alongside NSAID therapy. Misoprostol is readily available from the GI tract with an extensive first-pass metabolism, reaching peak levels in 60–90 minutes, with a brief half-life of 20–40 minutes.
Table 31.9 is a drug prototype table for misoprostol. It lists drug class, mechanism of action, adult dosage, indications, therapeutic effects, drug and food interactions, adverse effects, and contraindications.
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Drug Class
Prostaglandin analogue Mechanism of Action Acts as a synthetic prostaglandin E1 analogue with both antisecretory and mucosal protective properties in response to various gastric stimuli (meals, histamine, pentagastrin, and coffee) |
Drug Dosage
200 mcg 4 times daily with food; if dose is not tolerated, a dose of 100 mcg can be used. |
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Indications
Prevention of NSAID-induced gastric ulcers Therapeutic Effects Inhibits both basal and nocturnal gastric acid secretions |
Drug Interactions
Oxytocin Food Interactions No significant interaction |
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Adverse Effects
Diarrhea/constipation Abdominal pain Dysmenorrhea/spotting Uterine contractions Postmenopausal bleeding Flatulence Headache |
Contraindications
Hypersensitivity to prostaglandins Pregnancy Caution: Cardiovascular disease People of childbearing age |
Adverse Effects and Contraindications
Common adverse effects of mucosal protectants include hyperglycemia, dizziness, insomnia, and GI symptoms such as nausea, vomiting, diarrhea, and flatulence. Contraindications include hypersensitivity.
Typical adverse effects of prostaglandin analogues include headache, diarrhea or constipation, abdominal pain, flatulence, and gynecological symptoms such as dysmenorrhea , vaginal bleeding, uterine contractions, and postmenopausal bleeding. Contraindications include hypersensitivity to prostaglandins and pregnancy. Misoprostol may endanger pregnancy (may cause abortion) and cause harm to the fetus when administered to a pregnant client.
Nursing Implications
The nurse should do the following for clients who are taking mucosal protectants and prostaglandin analogues:
- Prior to administering, assess the client’s medical history, current drug list, and allergies.
- Educate the client regarding short-term duration of use for these medications, typically 4–8 weeks.
- Inform clients of childbearing age about the potential risk to the fetus, which could result in a miscarriage.
- Provide the client with teaching regarding the drug and when to call the health care provider. See below for additional client teaching guidelines.
Client Teaching Guidelines
The client taking a mucosal protectant and prostaglandin analogue should:
- Adhere to the dosing regimen prescribed by the health care provider, typically short-term administration of 4–8 weeks.
- When using misoprostol, report symptoms of abnormal vaginal bleeding or uterine cramping to the health care provider as these can represent serious adverse effects.
The client taking a mucosal protectant and prostaglandin analogue should not:
- Use prostaglandin analogues if pregnant due to the risk of fetal demise.
FDA Black Box Warning
Misoprostol
Misoprostol can cause spontaneous abortion, premature birth, or birth defects.