The safety of using H2 blockers in children has not been conclusively established, although new research indicates that premature infants who are given the drugs may have a slightly increased risk of developing necrotizing enterocolitis, a life-threatening bowel infection. However, evidence suggests that other children who take these drugs do not experience adverse events that are significantly different from those experienced by adults. Thus, the decision to use H2 blockers should be made on an individual basis, after careful consideration of risks, benefits and alternatives for that particular child.

Elderly adults may experience increased side effects associated with the central nervous system, including confusion and dizziness. In addition, dosage levels may have to be adjusted for elderly patients who have kidney disease.