Medication Summary
If a patient with histamine fish poisoning is ill enough to require treatment, antihistamines are used to counteract the symptoms; both histamine 1 (H1) and histamine 2 (H2) blockers may be used. Epinephrine or other adrenergic agents are rarely necessary because the entire cascade of mediators released by a true allergic reaction is not found in histamine poisoning, but adrenergic agents may be considered in the rare case of secondary bronchospasm or refractory hypotension associated with this type of poisoning. Corticosteroids are generally not indicated, except in cases of severe bronchospasm and angioedema.
Antihistamines, 1st Generation
Class Summary
These agents are used to reverse symptoms of the causative agent (ie, histamine). Initiate treatment with H1 blockers. H2 blockers may be added for synergistic effects.
Diphenhydramine (Benadryl, Aler-Dryl, Anti-Hist, Diphen)
An H1 blocker, diphenhydramine is considered the drug of choice for histamine fish poisoning. It may be given orally or intravenously. It provides relief of symptoms caused by release of histamine.
Hydroxyzine (Vistaril)
Hydroxyzine antagonizes H1 receptors in the periphery and may suppress histamine activity in the subcortical region of the central nervous system (CNS). This agent is used to manage histamine-mediated pruritus; it is an alternative to diphenhydramine.
Histamine2 Antagonists
Class Summary
These agents block H2 receptors of gastric parietal cells, leading to inhibition of gastric secretions. They can be used in combination with H1 blockers for patients with severe histamine fish poisoning that does not respond to H1 blockers alone.
Famotidine (Pepcid, Acid Reducer, Heartburn Relief)
Famotidine is an H2 antagonist that, when combined with an H1 type, may be useful in treating allergic reactions that do not respond to H1 antagonists alone.
Ranitidine (Zantac, Zantac 150 Maximum Strength, Zantac 75)
Ranitidine is a competitive, reversible inhibitor of histamine at the H2 receptor that may be used in conjunction with H1-blockers for severely symptomatic cases. It has fewer drug interactions than cimetidine and may be better for patients who take other medications metabolized by the cytochrome p450 system.
Cimetidine (Tagamet HB)
Cimetidine is an H2 antagonist that, when combined with an H1 type, may be useful in treating allergic reactions that do not respond to H1 antagonists alone..
Corticosteroids
Class Summary
These agents elicit anti-inflammatory and immunosuppressive properties and cause profound and varied metabolic effects. They modify the body's immune response to certain stimuli.
Methylprednisolone (Medrol, Medrol-Pak, Dosepak, Depo-Medrol, Solu-Medrol, A-Methapred)
Methylprednisolone is a glucocorticoid that ameliorates delayed effects of anaphylactoid reactions and may limit biphasic anaphylaxis.
Prednisone (Deltasone, Rayos, Prednisone Intensol, Sterapred, Sterapred DS)
Prednisone, a commonly used oral agent, may decrease inflammation by reversing increased capillary permeability and suppressing polymorphonuclear leukocyte (PMN) activity. It must be metabolized to the active metabolite prednisolone for it to have an effect. Conversion may be impaired in liver disease.
Prednisolone (Pediapred, Prelone, Orapred, Millipred)
Prednisolone controls inflammation by suppressing migration of PMNs and fibroblasts, reversing capillary permeability, and stabilizing lysosomes at cellular level. Since prednisolone is extensively metabolized in liver, there may be enhanced effect on patients with cirrhosis.
Beta2 Agonists
Class Summary
These agents relax the bronchial smooth muscle to relieve bronchospasm.
Albuterol (Proventil HFA, Ventolin HFA, Proair HFA, AccuNeb Vospire ER)
Albuterol stimulates adenyl cyclase to convert adenosine triphosphate (ATP) to cyclic adenosine monophosphate (cAMP), relaxing bronchial smooth muscle and causing bronchodilation. It has little effect on cardiac muscle contractility. This agent may decrease mediator release from mast cells and basophils and inhibit airway microvascular leakage. It is available as liquid for nebulizer use, in metered-dose inhalers, and dry powder inhalers.
Alpha/Beta Agonists
Class Summary
Sympathomimetic agents produce direct or indirect stimulation of adrenergic receptors and have various actions depending on the specific receptors involved.
Epinephrine (EpiPen, EpiPen Jr, Adrenaclick, Auvi-Q, Adrenalin)
Epinephrine stimulates alpha-, beta1, and beta2-adrenergic receptors, which, in turn, results in bronchodilation, increased peripheral vascular resistance, hypertension, increased chronotropic cardiac activity, and positive inotropic effects. It is the drug of choice for emergency treatment of severe allergic reactions, but provides relief for patients with histamine fish toxicity mistaken for allergic reactions.
Anticholinergics, Inhaled
Class Summary
These agents produce bronchodilation and are synergistic when used with a beta2-agonist.
Ipratropium (Atrovent, Atrovent HFA)
Ipratropium is a quaternary ammonium anticholinergic bronchodilator acting at muscarinic receptors of the parasympathetic nervous system. It is chemically related to atropine. Ipratropium has antisecretory properties and, when applied locally, inhibits secretions from serous and seromucous glands lining the nasal mucosa. It may be particularly useful for the treatment of histamine-induced bronchospasm.
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Mackerel.
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An example of a typical histamine toxicity rash, in this case from tuna. Image courtesy of Amanda Oakley, MBChB, FRACP.
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An example of a typical histamine toxicity rash, in this case from tuna. Image courtesy of Amanda Oakley, MBChB, FRACP.
