tobacco smoking
Ranitidine (Zantac) Contraindications and Precautions
Ranitidine is contraindicated in any patient hypersensitive to the drug or its components. Cross-sensitivity in this class of compounds has been observed, so ranitidine should be administered with caution to patients with a history of H2-blocker hypersensitivity. An incidence of cross-reactivity among this class of agents is not currently available.
Symptomatic response to therapy with ranitidine does not preclude the presence of gastric cancer. In the patient who is self-medicating with OTC ranitidine formulations, the continuation of heartburn, acid indigestion, or dyspepsia beyond 2 weeks signals the need to consult a health-care professional for evaluation.
Symptomatic response to therapy with ranitidine does not preclude the presence of H. pylori infection. Ranitidine therapy does not appear to interfere with the sensitivity of gastric urease biopsy or urea breath-tests for the detection of H. pylori in most patients. H2-blockers, as single agents, will not eradicate H. pylori infection, if present.
Studies in patients with hepatic dysfunction (compensated cirrhosis) indicate that there are minor, but clinically insignificant, alterations in ranitidine half-life, distribution, clearance, and bioavailability.
Ranitidine should be used cautiously in those patients with renal disease, specifically in those with renal impairment or renal failure. Accumulation of ranitidine can occur. Ranitidine dosage should be reduced in patients with creatinine clearances of less than 50 ml/min (see Dosage). No special precautions have been advised for the elderly, but some older patients may exhibit decreased renal function. Accumulation of ranitidine can occur. Dosage adjustments may be necessary in some older individuals based on renal function. Critically ill, elderly patients have been noted in some uncontrolled studies to be more likely to exhibit central nervous system (CNS) reactions to the H2-blockers.
The safety and efficacy of ranitidine have been established in children and infants from 1 month to 16 years of age for most indications. Dosages and efficacy have not been established for hypersecretory conditions. Ranitidine has been used successfully in critically ill children and infants for the purpose of stress-ulcer or acid-reflux prophylaxis (see Dosage). There is limited information on ranitidine use in neonates. Neonatal prematurity results in decreased ranitidine elimination compared to term neonates and requires dosage adjustment (see Dosage). Self-medication (i.e., OTC) in children under the age of 12 years is not recommended.
Ranitidine is classified in FDA pregnancy category B. Animal studies have not demonstrated a risk to the fetus but there are no adequate studies in pregnant women. Ranitidine does cross the placenta, but limited epidemiological evidence has not suggested an association between the drug and congenital defects in first trimester exposure. Mean fetal: maternal ratios are approximately 0.9 after IV administration versus 0.4 for oral dosages. Risk versus benefit should be considered prior to use, and use should take place under the guidance of a qualified health care professional. Ranitidine should be used in pregnancy only when necessary, when safer drugs such
as antacids have failed. Self-medication during pregnancy is not recommended. Pregnant patients should see their health care professional for a proper diagnosis and for treatment recommendations. Limited use of single dosages of ranitidine for reducing gastric acid prior to obstetric delivery, including caesarian section, have not been noted to adversely affect labor or neonatal outcomes.
Ranitidine is excreted into breast milk and should be used with caution in a woman who is breast-feeding her infant. Milk concentrations increase with time after the administration of a maternal oral dose. Mean maternal milk: plasma ratios at 2 and 6 hours after a single oral dose, ratios are 1.9 and 6.7 respectively. The effect of ranitidine or the resultant decrease in gastric acidity on the nursing infant is not known. However, the American Academy of Pediatrics has considered the use of cimetidine, a related agent that is also highly excreted into breast milk, to be compatible with breast-feeding due to a lack of reported adverse effects in nursing infants. Risk-benefit ratios should be considered, taking into account the importance of the medication to the mother.
Rare reports have suggested that ranitidine may precipitate acute porphyric attacks in patients with acute porphyria. It is recommended that ranitidine be avoided in these patients.
Certain formulations of ranitidine (i.e., Zantac® EFFERdose® tablets) contain phenylalanine and should be used cautiously in patients with phenylketonuria. Patients with phenylketonuria should be warned that these dosage forms contain 16.84 mg of phenylalanine per 150 mg of ranitidine and 2.81 mg of phenylalanine per 25 mg of ranitidine.
Tobacco smoking appears to contribute to an increased risk of developing PUD and may also impair ulcer healing or increase the risk of ulcer recurrence.
[ Last revised: 4/13/2004 11:20:00 PM ]
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