Medication Summary
Epinephrine and systemic antihistamines (eg, diphenhydramine, cimetidine), topical or systemic steroids, menthol-containing creams, and prostaglandin-synthetase inhibitors, such as aspirin and indomethacin, all may be beneficial in treating dermatitis.
Rhinitis resulting from respiratory exposure may respond to antihistamines and systemic steroids. These are also useful for lower respiratory symptoms.
Beta-agonist aerosols or inhalers (eg, albuterol) may be beneficial for wheezing.
Analgesics may be required for caterpillar stings. The choice of agent should depend on the severity of symptoms. Mild cases may be treated adequately with oral opiates such as hydrocodone or oxycodone, while more severe pain initially may require parenteral agents such as morphine sulfate in the hospital setting.
Stings by the South American Lonomia species, which can cause consumptive coagulopathy with hemorrhagic diathesis and acute renal failure, may be treated with antifibrinolytics. If blood products are required, they must be given cautiously to avoid feeding fuel to an on-going consumptive coagulopathy. An antivenom against this species has been produced in Brazil. [18]
Antihistamines
Class Summary
Antihistamines prevent histamine response in sensory nerve endings and blood vessels. They are more effective in preventing a histamine response than in reversing it.
Diphenhydramine (Benadryl, Benylin, Bydramine)
Diphenhydramine is used for symptomatic relief of allergic symptoms caused by histamine released in response to allergens.
Chlorpheniramine (Chlor-Trimeton)
Chlorpheniramine competes with histamine for H1-receptor sites on effector cells in blood vessels and the respiratory tract.
Cimetidine (Tagamet)
Cimetidine is an H2 antagonist that, when combined with an H1 type, may be useful in treating itching and flushing in anaphylaxis, pruritus, urticaria, and contact dermatitis that do not respond to H1-receptor antagonists alone. Use it in addition to H1 antihistamines.
Corticosteroids
Class Summary
Their onset of action is approximately 4-6 hours, and they have limited benefit in the initial acute treatment of rapidly deteriorating anaphylactic patients. However, corticosteroids may benefit patients with persistent bronchospasm or hypotension.
Topical steroids can help reduce the cutaneous inflammatory response in caterpillar-induced dermatitis.
Methylprednisolone (Solu-Medrol)
Methylprednisolone decreases inflammation by suppressing the migration of polymorphonuclear leukocytes and reversing increased capillary permeability.
Prednisone (Deltasone, Orasone, Meticorten)
Prednisone decreases inflammation by suppressing the migration of polymorphonuclear leukocytes and reversing increased capillary permeability.
Topical hydrocortisone (Westcort, Dermacort, Cortaid)
Topical hydrocortisone is the drug of choice for reducing cutaneous inflammatory responses in caterpillar-induced dermatitis. It is an adrenocorticosteroid derivative suitable for application to skin or external mucous membranes. It has mineralocorticoid and glucocorticoid effects, resulting in anti-inflammatory activity.
Bronchodilators
Class Summary
Via combined alpha-adrenergic and beta-adrenergic agonist action, sympathomimetics are effective in reversing acute bronchospasm of allergic or irritant origin.
An additional option in the management of persistent bronchospasm is via anticholinergics. These agents block the action of acetylcholine at parasympathetic sites in bronchial smooth muscle, causing bronchodilation.
Albuterol (Ventolin, Proventil)
Albuterol is a beta-agonist useful in the treatment of bronchospasm refractory to epinephrine. It relaxes bronchial smooth muscle by acting on beta2 receptors with little effect on the heart rate.
Epinephrine (Adrenalin, EpiPen)
Alpha-agonist effects increase peripheral vascular resistance and reverse peripheral vasodilatation, vascular permeability, and systemic hypotension. Conversely, beta-agonist effects produce bronchodilatation, cause positive inotropic and chronotropic cardiac activity, and result in an increased production of intracellular cAMP.
Ipratropium bromide (Atrovent)
Ipratropium bromide is a synthetic quaternary anticholinergic ammonium compound chemically related to atropine; it has antisecretory properties; when applied locally, it inhibits secretions from serous and seromucous glands lining nasal mucosa.
Analgesics
Class Summary
Pain control is essential to quality patient care. Most analgesics have sedating properties, which may be beneficial for patients who have sustained severe caterpillar stings.
Aspirin (Anacin, Ascriptin, Bayer Aspirin, Bufferin)
Aspirin is used for treatment of mild to moderate pain and headache.
Morphine sulfate (Duramorph, Astramorph, MS Contin)
Parenteral opiates may be necessary to manage extreme pain in patients with severe stings.
Hydrocodone and acetaminophen (Vicodin)
This drug combination is indicated for relief of moderate to severe pain.
Nonsteroidal anti-inflammatory agents (NSAIDs)
Class Summary
NSAIDs can be effective in reducing discomfort associated with caterpillar-induced dermatitis.
Indomethacin (Indocin, Indochron ER)
Indomethacin is a commonly prescribed NSAID used for reducing inflammatory responses. It is rapidly absorbed; metabolism occurs in the liver by demethylation, deacetylation, and glucuronide conjugation; it inhibits prostaglandin synthesis.
Cardiovascular agents
Class Summary
These agents may be used to support organ perfusion in hypotensive patients unresponsive to intravenous volume expansion.
Dopamine (Intropin)
Dopamine may be required to support blood pressure in the face of hypotension caused by anaphylactic/anaphylactoid reaction that is unresponsive to fluids and epinephrine.
Toxoid
Class Summary
These are used for tetanus immunization. A booster injection in previously immunized individuals is recommended to prevent this potentially lethal syndrome.
Tetanus toxoid adsorbed or fluid
Tetanus toxoid adsorbed or fluid is used to induce active immunity against tetanus in selected patients. The immunizing agent of choice for most adults and children older than 7 years are tetanus and diphtheria toxoids. It is necessary to administer booster doses to maintain tetanus immunity throughout life.
Pregnant patients should receive only tetanus toxoid, not a diphtheria antigen-containing product.
In children and adults, it may be administered into the deltoid or midlateral thigh muscles. In infants, the preferred site of administration is mid thigh laterally.
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Caterpillar envenomations. Puss caterpillar or asp. Photo courtesy of the Arizona Poison and Drug Information Center.
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Distinguishing dangerous from harmless caterpillars can be difficult, and handling any caterpillar with bare skin should be avoided. These are harmless tomato hornworm caterpillars (larval form of the five-spotted hawk moth [Manduca quinquemaculata])
