An 18-year-old woman took a dose of a friends nizatidine for an upset stomach. About one hour after taking 150 mg of nizatidine she experienced shortness of breath, tachypnoea, wheezing and a mild visible swelling of the neck. On presentation to the Emergency Department she was visibly distressed. Her lung expansion was poor with diffuse coarse polyphonic inspiratory and expiratory wheezes. There was no rash. After treatment with adrenaline, promethazine and prednisolone, she improved rapidly.
We can only find two other reports of allergic reactions to nizatidine1,2, (although cases of allergy to other H2 histamine receptor antagonists have been published). The first report described a leukocytoclastic vasculitis associated with nizatidine. The second described a situation which was very similar to our case. In the report the patient was rechallenged with nizatidine and other H2 antagonists. Results of the oral challenge were negative for cimetidine, ranitidine and famotidine. However, within 15 minutes of nizatadine administration the patient again experienced laryngeal oppression, dysphonia, dysphagia, dry mouth, moderate flushing and generalised pruritis.
The ability of H2 histamine antagonists to increase serum histamine by displacing it from its receptors is well known, particularly after a rapid intravenous infusion. A similar effect would account for the appearance of anaphylactoid symptoms on some occasions. However, the second study2 suggested an anaphylactic, rather than anaphylactoid, mechanism caused the symptoms as there was no reaction to the other H2 antagonists.
Our case also shows the dangers of using other peoples medicines.
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