You are in: eMedicine Specialties > Pediatrics: Cardiac Disease and Critical Care Medicine > Toxicology Toxicity, Mushrooms - MuscarineArticle Last Updated: Feb 12, 2008AUTHOR AND EDITOR INFORMATIONAuthor: Martin I Herman, MD, FACEP, FAAP, Professor, Department of Pediatrics, Division of Critical Care and Emergency Medicine, University of Tennessee Health Sciences Center; President, Pediatric Emergency Services Specialists,PC; Assistant Medical Director of Emergency Services, LeBonheur Children's Medical Center Martin I Herman is a member of the following medical societies: American Academy of Pediatrics, American College of Emergency Physicians, American Medical Association, and Tennessee Medical Association Coauthor(s): Peter Chyka, PharmD, FACCT, DABAT, Professor, Department of Clinical Pharmacy, University of Tennessee Health Science Center Editors: Michael E Mullins, MD, Assistant Professor, Department of Emergency Medicine, Washington University School of Medicine; Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine.com, Inc; Jeffrey R Tucker, MD, Assistant Professor, Department of Pediatrics, Division of Emergency Medicine, University of Connecticut and Connecticut Children's Medical Center; Paul D Petry, DO, FACOP, FAAP, Consulting Staff, Freeman Pediatric Care, Freeman Health System; Timothy E Corden, MD, Associate Professor of Pediatrics, Co-Director, Policy Core, Injury Research Center, Medical College of Wisconsin; Associate Director, PICU, Children's Hospital of Wisconsin Author and Editor Disclosure Synonyms and related keywords: muscarine, cholinergic syndrome, Amanita muscaria, A muscaria, Inocybe, Clitocybe, Clitocybe dealbata, Boletus, Omphalotus, Amanita mushroom poisoning, toadstool poisoning, sweating mushroom, truffles, toadstool, cyclopeptide, ibotenic acid, muscimol, gyromitrin, coprine, psilocybin, GI irritants, seizures, renal failure, liver failure, hemolytic anemia, rhabdomyolysis, heart block, asthma, prostate hypertrophy, gastric disorders, gastric outlet obstruction, reflex tachycardia, bradycardia, bronchospasm, hypotension INTRODUCTIONBackgroundMuscarine was first extracted from Amanita muscaria (fly agaric) in 1869. It played an important part in delineating the role of acetylcholine (ACh) in neurohumoral physiology. In fact, since the late 1800s, pharmacologists have referred to the effects of stimulation of postganglionic choline receptors as the muscarinic effects of ACh. An ironic note is that A muscaria provided the first source of muscarine (hence its name) but actually contains miniscule amounts of muscarine (0.005%). To produce a toxic effect, mushrooms must contain at least 0.01% of muscarine (as described in the Poisindex).1 Mushrooms from the genera Inocybe and Clitocybe reliably contain sufficient amounts of this toxin. In fact, one species, Clitocybe dealbata, is so well known for its reliably high muscarine content that it is commonly referred to as the sweating mushroom. Mushrooms in the genera Boletus, Omphalotus, or Amanita may also contain some muscarine. Bear in mind that the muscarine content may vary from plant to plant, depending on where they are grown, on how they are prepared, or on how they are stored. Mushrooms, which are classified as fungi, differ from other plants because they do not have chlorophyll. They have been a part of the human diet for years because they are a source of protein and essential amino acids. The edible varieties satisfy gustatory pleasures while providing nutritional value. They are generally low in calories and cholesterol and can improve the immune system and blood pressure. Because they are promoted for their nutrient values, many grocery stores now carry various commercially grown mushrooms, including shiitake, portabella, morels, chanterelle, oyster, and other mushrooms. The commercially grown, cultured mushrooms are the safest to enjoy. Increased awareness and interest in the large variety of mushrooms found around the world has led to growing interest in foraging for wild mushrooms. Although finding mushroom delicacies in the wild may be satisfying, caution is required because many mushrooms contain deadly toxins. The challenge to all who forage for mushrooms is that they must be able to distinguish truffles (edible varieties) from toadstools (from the German todesstuhl, which means "death stool"). Mistaking a toxic mushroom for an edible one is the most common cause of poisoning. This problem might be especially important among immigrant populations if they mistake a toxic variety indigenous to their new country for a nontoxic variety they were used to eating in their homeland. Fortunately, mushroom poisoning is rare. Of the roughly 5000 known mushroom species, approximately 200-300 are edible, and only 50-100 are poisonous. The odds are clearly favorable when one ingests an unidentified mushroom. However, approximately 7000 mushroom ingestions are reported every year to the American Association of Poison Control Centers (AAPCC) Poison Exposure Database.2 Children and adolescents younger than 19 years account for 78% of all reported ingestions. Many ingestions in children younger than 6 years are unintentional and consist of a child simply tasting a mushroom found growing in their yard or play area. This is not the case for ingestions in older children. Adolescents are most likely to engage in a misguided attempt to experience hallucinogenic effects of magic mushrooms or to intentionally ingest toxic mushrooms to commit suicide. Of note, poisonings can also occur when otherwise edible mushrooms are improperly stored, prepared, or cooked. Some unintentional ingestions might result from the purchase of misidentified or adulterated mushroom products through unregulated marketers on the Internet or other illicit sources. Muscarine is one of the commonly accepted classes of mushroom toxins. Toxin groups include the following:
Distribution and recognition of mushrooms Mushrooms that contain muscarine are commonly found in yards and public parks. Their prevalence and enticing appearance may pose a challenge to parents as they try to keep their children from sampling these potentially toxic plants. Clitocybe, Inocybe, and Amanita species are among those most commonly involved in muscarinic poisoning. Being able to recognizing these mushrooms and to educate parents and children about their dangers is important. Clitocybe mushrooms are found as single specimens on lawns in the summer and fall. The mushrooms are whitish tan-to-gray and have 15- to 33-mm caps. Their stalks are hairless and are 1- to 5-cm long. Their gills are decurrent (running down the stalk), and the spores are white. Inocybe mushrooms are typically found in or under hardwoods and conifers in the summer and fall. The mushrooms are small and brown and have conical caps as large as 6 cm in diameter. Stalks are 2-10 cm and have fine, brown-to-white hairs. The gills are notches, and the spores are brown. A muscaria can occur singly or in groups, and it is found on the ground of forests, grassy areas, and lawns, especially under trees. The mushroom has a scarlet cap 5-30 cm in diameter, with warts. The stalk is white, frequently hollow, and often as long as 15-20 cm. A prominent cup (volva) is found at the bottom of the stalk with numerous rings extending superiorly. The gills are free and white. The spores are also white. The appearance varies depending on the geographic location. The scarlet red cap is found predominantly in western parts of North America. In eastern North America, the cap is orange to yellow-orange. Classification systems Because of the large numbers of mushroom species and difficulties in their identification, toxicologists have struggled with developing a system to facilitate the recognition of mushrooms and the treatment of mushroom ingestion. In 1987, a group started in Germany proposed classifying mushroom poisonings on the basis of (1) a description of the mushroom, (2) toxicologic analysis, and (3) the patient's presenting signs and symptoms. Because the lag time to toxicity appears to be an important factor, any system of classification should incorporate this lag. According to several observers, latent periods of >12 hours differentiate the lethal amatoxin poisonings from less serious, early-onset poisonings involving other toxins. People working with mushroom poisonings have known that notable mushroom toxicity can occur before 12 hours and suggest use of a lag time of >6 hours to separate the clinically significant ingestions of amanitin and gyromitrin from less toxic ingestions. Of course, serious ingestions may be neglected if they have a short onset time to GI irritation followed by serious problems, such as seizures, renal failure, liver failure, or hemolytic anemia. To refine the current classification scheme, a toxin-directed system was developed. Mushroom ingestions may be classified on the basis of evidence of poisoning from the following toxins: amanitin, orellanine, gyromitrin, muscarine, pantherine, psilocybin, coprine, Paxillus toxin, and miscellaneous GI irritants. This system, which was originally proposed in Europe, was adapted for use in the United States. Table 1 below shows this toxin-based scheme. US and European Classes of Mushroom Toxins
An unfortunate feature is that all of the systems of nomenclature fail to recognize newly discovered toxic effects, such as those causing acute renal failure, delayed renal failure, rhabdomyolysis, and delayed CNS failure. To address these shortcomings, some have proposed simplifying the classification system by basing it on whether the toxins are hepatotoxic, nephrotoxic, neurotoxic, psychotropic, myotoxic, or gastroenteric. Old taxonomy clearly fails to consider the lag times of various poisons. Although the 6-hour cutoff works well for amatoxin and gyromitrin toxicity, it causes some early onset toxicities to be missed and underestimates the need for the prolonged care needed in patients with delayed-onset toxicities. When one combines the type of toxin and the onset of its effects, a new, time-to-onset–stratified, syndromic system emerges. This approach may enable early detection and enable application specific therapies, including transplantation. A classification of 14 syndromic categories of mushroom poisoning has been proposed. This classification system includes an improved definition of the miscellaneous category but has yet to be widely adopted.3 Muscarine is designated as an early-onset (<6 h) cholinergic neurotoxin in this new system.
Perhaps clinicians will use this new syndromic classification system in the near future to quickly recognize possible mushroom poisonings and to make appropriate decisions regarding intervention, observation, and follow-up. PathophysiologyMechanism of action As noted above, muscarine is one of the 8 major mushroom toxins. It exerts its effects by means of the autonomic nervous system. The autonomic nervous system is composed of the sympathetic and parasympathetic systems and uses ACh as the chemical transmitter at both preganglionic and postganglionic synapses in the parasympathetic system. ACh is also the neurotransmitter at sympathetic preganglionic synapses, at some sympathetic postganglionic synapses, at the neuromuscular junction (somatic nervous system), and at some sites in the CNS. Nerve fibers that release ACh from their endings are described as cholinergic fibers. ACh receptors are ligand-gated cation channels composed of 4 polypeptide subunits arranged in the form (a2)(b)(g)(d). Two main classes of ACh receptors are recognized and are differentiated by their response to nicotine or muscarine. When ACh stimulates preganglionic synapses, it produces sympathetic effects at various end organs of the autonomic system. These effects can be reproduced with the administration of nicotine as therefore are known as the nicotinic effects of ACh. ACh may also stimulate postganglionic receptors to produce effects such as salivation, lacrimation, defecation, micturition, sweating, miosis, bradycardia, and bronchospasm. Muscarine produces these effects, and hence they are referred to as muscarinic effects, and the postganglionic receptors are called muscarine receptors. Muscarinic receptors are the most diffuse receptors and are G-protein coupled. Two subgroups have been identified: M1 and M2. M1 receptors are excitatory, and M2 receptors are inhibitory. By convention, the muscarinic effects of various drugs are also referred to as cholinergic effects. Muscarine is a quaternary trimethyl ammonium salt of 2-methyl-3-oxy-5-(amino)-tetrahydrofuran. It can stimulate both the M1 and M2 types of postganglionic cholinergic receptors (muscarinic receptors). When it does, it results in parasympathetic stimulation similar to that caused by the release of endogenous ACh. Because it is a quaternary salt, muscarine does not readily cross the blood-brain barrier. As a result, it causes few, if any, CNS symptoms. Muscarine is not metabolized by cholinesterase and therefore has a long biologic half-life. Toxicity The lethal dose is estimated to be 40-180 mg. FrequencyUnited StatesIn 2005, 7146 mushroom ingestions were reported by US poison control centers.2 Nineteen (0.3%) were attributed to the muscarine-containing group of toadstools. Four (21%) of the 19 patients were children younger than 19 years of age. The 15 others (79%) were over 19 years. InternationalIn Europe, the incidence of all types of toxic mushroom ingestions is higher than that of the United States. An average of 70 cases per year occurs in Japan. Other countries, such as China and South Africa, also report mushroom toxicities. Whether these toxicities are due to mushrooms containing muscarine is not known. Mortality/MorbidityFatalities from mushroom poisoning are rare but do occur.
Age
CLINICALHistoryAssess the following:
PhysicalSigns and symptoms related to the ingestion of a muscarine-containing mushroom typically appear after 0.5-2 hours and may last 6-24 hours. Muscarinic effects, such as sweating, salivation, lacrimation, urination, defecation, gastric cramping, miosis, emesis, bronchospasm, and bradycardia are seen. Profuse sweating is a prominent feature and should alert the provider to the possibility of a cholinergic poisoning. The acronyms SLUDGE (salivation, urination, diarrhea, gastric upset, and emesis) and DUMBBELS (diarrhea, urination, miosis, bradycardia, bronchospasm, emesis, lacrimation, and salivation) may be useful memory aids.
Causes
DIFFERENTIALSAsthma Gastroenteritis Heart Failure, Congestive Hypoglycemia Serum Sickness
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| Drug Name | Atropine sulfate injection |
|---|---|
| Description | Acts at parasympathetic sites in smooth muscle to block response to ACh. |
| Adult Dose | 0.4-2 mg IV/IM; repeat q20-30min prn to control bronchial secretions |
| Pediatric Dose | 0.02 mg/kg IV/IM; minimal dose is 0.1 mg; repeat q10-20min prn to control secretions |
| Contraindications | Documented hypersensitivity; thyrotoxicosis, narrow-angle glaucoma, tachycardia, obstructive uropathy, paralytic ileus, toxic megacolon, asthma, and myasthenia gravis; benefits may outweigh risks if cholinergic symptoms life-threatening |
| Interactions | Additive effects with coadministration with other anticholinergics; may increase pharmacologic effects of atenolol and digoxin; may decrease antipsychotic effects of phenothiazines may decrease; tricyclic antidepressants with anticholinergic activity may increase effects |
| Pregnancy | C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus |
| Precautions | Avoid in Down syndrome and brain damage to prevent hyperreactive response; avoid in coronary heart disease, tachycardia, congestive heart failure (CHF), cardiac arrhythmias, and hypertension; caution in peritonitis, ulcerative colitis, hepatic disease, and hiatal hernia with reflux esophagitis; in prostatic hypertrophy, prostatism can cause dysuria (catheterization may be required) |
| Drug Name | Glycopyrrolate (Robinul) |
|---|---|
| Description | Acts in smooth muscle, CNS, and secretory glands, where it blocks action of ACh at parasympathetic sites. |
| Adult Dose | 0.1-0.2 mg IV; repeat q20-30min prn to control bronchial secretions |
| Pediatric Dose | 0.008 mg/kg (8 mcg/kg) IV; repeat prn to control secretions; not to exceed 0.2 mg/dose |
| Contraindications | Documented hypersensitivity; narrow-angle glaucoma, tachycardia, ulcerative colitis, paralytic ileus, acute hemorrhage, obstructive uropathy, toxic megacolon, asthma, myasthenia gravis |
| Interactions | Drugs with anticholinergic effects (eg, antihistamines, clozapine, digoxin, haloperidol, loxapine, metoclopramide, tricyclic antidepressants) have additive effects; levodopa decreases effects; amantadine and cyclopropane increase toxicity |
| Pregnancy | B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals |
| Precautions | May increase risk of megacolon, hyperthyroidism, CHF, coronary heart disease (CAD), hiatal hernia, and benign prostatic hyperplasia (BPH); may cause hyperactive response in Down syndrome |
These provide reasonable reversal of the bronchospastic actions of the toxins.
| Drug Name | Albuterol sulfate (Proventil, Ventolin) |
|---|---|
| Description | Works by means of beta-adrenergic receptors to induce bronchodilation. |
| Adult Dose | Nebulizer: 2.5-5 mg (0.5-1 mL of 5% solution)/dose inhaled by nebulizer Alternative: 1-2 inhalations/dose by metered-dose inhaler; may repeat prn |
| Pediatric Dose | Administer as in adults |
| Contraindications | Documented hypersensitivity |
| Interactions | Beta-adrenergic blockers antagonize effects; inhaled ipratropium may increase duration of albuterol-induced bronchodilatation; cardiovascular effects may increase with monoamine oxidase inhibitors (MAOIs), inhaled anesthetics, tricyclic antidepressants, and sympathomimetic agents |
| Pregnancy | C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus |
| Precautions | Caution in hyperthyroidism, diabetes mellitus, and cardiovascular disorders |
These are used to stop or control seizures that may occur.
| Drug Name | Diazepam (Valium) |
|---|---|
| Description | Depresses all levels of CNS (eg, limbic and reticular formations), possibly by increasing activity of gamma-aminobutyric acid (GABA). |
| Adult Dose | 2.5-10 mg IV; may repeat q5-10min |
| Pediatric Dose | 0.1-0.2 mg/kg IV; may repeat q15-20 min; not to exceed cumulative dose of 5 mg |
| Contraindications | Documented hypersensitivity; narrow-angle glaucoma |
| Interactions | Concurrent phenothiazines, barbiturates, alcohols, and MAOIs increase CNS toxicity |
| Pregnancy | D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus |
| Precautions | Caution with other CNS depressants, low albumin levels, or hepatic disease (may increase toxicity) |
| Drug Name | Lorazepam (Ativan) |
|---|---|
| Description | Useful to treat delirium, seizures, or agitation. May depress all levels of CNS (eg, limbic and reticular formations) by increasing action of GABA (major inhibitory neurotransmitter in brain). |
| Adult Dose | 4-8 mg IV infused over 2-5 min; administer 4 mg initially; may repeat in 10-15 min |
| Pediatric Dose | 0.05-0.1 mg/kg IV infused over 2-5 min; may repeat in 10-15 min prn; not to exceed 2 mg/dose |
| Contraindications | Documented hypersensitivity; preexisting CNS depression, hypotension, and narrow-angle glaucoma |
| Interactions | CNS toxicity increases with concurrent use of alcohol, phenothiazines, barbiturates, and MAOIs |
| Pregnancy | D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus |
| Precautions | Caution in renal or hepatic impairment, myasthenia gravis, organic brain syndrome, or Parkinson disease; monitor blood pressure after administration (adjust dose prn) |
| Drug Name | Midazolam (Versed) |
|---|---|
| Description | Useful to treat delirium, seizures, or agitation. Alternative in termination of refractory status epilepticus. Because water soluble, requires approximately 3 times longer than diazepam to achieve peak EEG effects. Therefore, wait 2-3 min to fully evaluate sedative effects before starting procedure or repeating dose. |
| Adult Dose | 2.5-5 mg IV; may repeat in 10-15 min |
| Pediatric Dose | 0.05-0.1 mg/kg IV, not to exceed 2 mg or the adult dose, or intranasally |
| Contraindications | Documented hypersensitivity; preexisting hypotension, narrow-angle glaucoma, and sensitivity to propylene glycol (diluent) |
| Interactions | Theophyllines may antagonize sedative effects; narcotics and erythromycin may accentuate sedative effects because of decreased clearance |
| Pregnancy | D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus |
| Precautions | Caution in CHF, pulmonary disease, renal impairment, and hepatic failure |
| Drug Name | Phenobarbital (Luminal) |
|---|---|
| Description | In status epilepticus, achieves therapeutic levels as quickly as possible. IV dose may require approximately 15 min to attain peak levels in brain. If injected continuously until convulsions stop, brain concentrations may continue to increase and exceed those required to control seizures. Use minimal amount required and wait for anticonvulsant effect to develop before administering second dose. |
| Adult Dose | 600-1200 mg IV loading dose; may follow with maintenance dose after12 h prn |
| Pediatric Dose | 15-20 mg/kg IV loading dose; may follow with maintenance dose after 12 h prn |
| Contraindications | Documented hypersensitivity; severe respiratory disease, marked impairment of liver function, and nephritis |
| Interactions | May decrease effects of chloramphenicol, digitoxin, corticosteroids, carbamazepine, theophylline, verapamil, metronidazole, and anticoagulants (patients taking anticoagulants may require dose adjustments if drug added to or withdrawn from regimen); coadministration with alcohol may produce additive CNS effects and death; chloramphenicol, valproic acid, and MAOIs may increase toxicity; rifampin may decrease effects; induction of microsomal enzymes may decrease effects of PO contraceptives in women (must use additional contraception to prevent unwanted pregnancy; menstrual irregularities may occur) |
| Pregnancy | D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus |
| Precautions | Monitor respirations, especially if used with or shortly after benzodiazepines, observe for hypotension; in prolonged therapy, evaluate hematopoietic, renal, hepatic, and other organ systems; caution in fever, hyperthyroidism, diabetes mellitus, and severe anemia because adverse reactions can occur; caution in myasthenia gravis and myxedema |
Toxicity, Mushrooms - Muscarine excerpt
Article Last Updated: Feb 12, 2008