Medication Summary
Medications used to treat Hymenoptera stings include antihistamines (H1, H2), steroids, alpha- and beta-receptor agonists, and bronchodilators.
Antihistamines, 1st Generation
Class Summary
These drugs directly block effects of some venom and effects of endogenously released histamine.
Diphenhydramine (Benadryl, Aler-Dryl, Diphen, Genahist, Altaryl)
Diphenhydramine is the drug of choice for all stings. It is an H1 and partial H2 receptor blocker used for symptomatic relief of allergic symptoms caused by histamine released in response to allergens.
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.
Bronchodilators
Class Summary
Epinephrine causes vasoconstriction, bronchodilation, and increased cardiac output. The effects of albuterol and theophylline are more focused on bronchodilation.
Albuterol (Proventil HFA, Ventolin HFA, ProAir HFA, VoSpire ER)
Albuterol is an adjunctive treatment for bronchospasm given by nebulization, and it is a beta-agonist useful to treat bronchospasm refractory to epinephrine. It relaxes bronchial smooth muscle by action on beta2-receptors and has little effect on cardiac muscle contractility.
Corticosteroids
Class Summary
These drugs act to stabilize lymphocytes and to reduce release of endogenous vasoactive compounds.
Methylprednisolone (Solu-Medrol, Depo-Medrol)
Methylprednisolone may be useful in cases of generalized reaction unless contraindications exist. It may decrease inflammation in inflammatory and allergic reactions by reversing increased capillary permeability and suppressing PMN activity.
Prednisone (Deltasone, Prednisone Intensol, Rayos)
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 (Orapred, Millipred, Millipred DP, Veripred 20)
Prednisolone may decrease inflammation by reversing increased capillary permeability and suppressing polymorphonuclear leukocyte (PMN) activity.
Antidote, Hypoglycemia
Class Summary
Glucagon acts in the adipose tissue and liver to quickly stimulate gluconeogenesis, and thereby elevate blood glucose levels.
Glucagon (Glucagen HypoKit, Glucagon Emergency)
Glucagon is the drug of choice for severe anaphylaxis in patients taking beta-blockers (should be used in addition to epinephrine, not as a substitute).
Pancreatic alpha cells of the islets of Langerhans produce glucagon, a polypeptide hormone. It exerts the opposite effects of insulin on blood glucose. Glucagon elevates blood glucose levels by inhibiting glycogen synthesis and enhancing the formation of glucose from noncarbohydrate sources, such as proteins and fats (gluconeogenesis). It increases hydrolysis of glycogen to glucose (glycogenolysis) in the liver in addition to accelerating hepatic glycogenolysis and lipolysis in adipose tissue. Glucagon also increases the force of contractions in the heart and has a relaxant effect on the GI tract.
The dose used for anaphylaxis is higher than the usual dose of 1 mg (1 U) IV/IM/SC used to treat hypoglycemia.
Alpha/Beta Adrenergic Agonists
Class Summary
Sympathomimetic agents produce direct or indirect stimulation of adrenergic receptors and have various actions, depending on the specific receptors involved.
Epinephrine (Epi-Pen, Adrenaclick, Adrenalin, Adyphren)
Epinephrine is the drug of choice for systemic reactions. It has alpha-agonist effects that increase peripheral vascular resistance and reverse peripheral vasodilation, systemic hypotension, and vascular permeability. Conversely, the beta-agonist activity of epinephrine produces bronchodilation, chronotropic cardiac activity, and positive inotropic effects. Epinephrine may be self-administered through auto-injectors.
Histamine H2 Antagonists
Class Summary
These agents block H2 receptors of gastric parietal cells, leading to inhibition of gastric secretions. They can also be used in combination with H1 blockers for patients with severe histamine reactions that do not respond to H1 blockers alone.
Cimetidine (Tagamet HB)
Cimetidine is indicated for systemic reactions that do not respond completely to diphenhydramine, or when severity indicates a need for maximal treatment.
Famotidine (Pepcid, Heartburn Relief, Acid Reducer)
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, Deprizine FusePaq, Deprizine RapidPaq, 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.
Phosphodiesterase Enzyme Inhibitors, Nonselective
Class Summary
These agents are used as additional therapy for patients who remain in refractory status of bronchospasm despite maximal inhalational therapy and the use of corticosteroids. These medications may be administered intravenously.
Theophylline (Theo-24, Elixophyllin, Theocron)
Theophylline is used to relieve bronchospasm in resistant cases. It acts to decrease muscle tone in both small and large airways in the lungs, thus increasing ventilation. Efficacy in managing bronchodilation may be due to its potentiation of exogenous catecholamines, stimulation of endogenous catecholamine release, and diaphragmatic muscular relaxation. Its effects as a bronchodilator usually are seen at levels considered to be toxic (>20 mg/dL).
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Western paper wasp (Mischocyttarus flavitarsis) building a nest. By Sanjay Acharya (self-made at Sunnyvale, California, USA). Courtesy of Wikimedia Commons.
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Yellow jacket. By Richard Bartz, Munich aka Makro Freak (Own work). Courtesy of Wikimedia Commons.
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Fire ant bites. In less than 10 seconds, an unwary scientist was stung over 250 times on one leg when he carelessly knelt on a collapsed fire ant mound. The sterile pustules developed to this stage in 3 days. US Department of Agriculture. Courtesy of Wikimedia Commons.
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Fire ants. US Department of Agriculture. Courtesy of Wikimedia Commons.
