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Plant Poisoning, Hemlock: Treatment & Medication
Updated: Nov 7, 2008
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
- Multimedia
Treatment
Prehospital Care
For patients with possible hemlock poisoning, maintain the airway, obtain IV access airway, and assist with ventilation as needed.
Emergency Department Care
Rapidly assess and correct any life-threatening conditions. Since no antidote exists for either toxin, GI decontamination (if appropriate) and aggressive supportive care are mainstays of treatment for poison hemlock.
- Secure airway.
- Decontaminate GI tract if timing is appropriate.
- If no contraindications exist, gastric lavage may be of limited benefit if performed rapidly after the ingestion.
- Administer activated charcoal if the patient presents within 1 hour of ingestion. Ipecac should not be used.
- Treat seizures with benzodiazepines; use barbiturates if needed.
- Provide prophylaxis with water hemlock ingestion.
- Benzodiazepines and barbiturates help control agitation and raise the seizure threshold.
- Aggressively administer IV fluids for dehydration or rhabdomyolysis.
- Replete volume if signs of hypovolemia or hypotension are present.
- Correct electrolyte abnormalities.
- Administer fluids with sodium bicarbonate for urinary alkalinization if evidence of rhabdomyolysis exists. If using sodium bicarbonate, mixing it in 5% dextrose in water (D5W) is important to limit the amount of sodium load.
- Potassium levels should be monitored and corrected as needed.
- Administer antiemetics. Many antiemetics may lower the seizure threshold and should be used cautiously.
- Provide ventilatory support, if necessary.
Consultations
A regional poison center or a medical toxicologist can assist with patient treatment and potentially with plant identification.
Medication
Do not use ipecac during gastric decontamination because of risk of inducing seizures. Other agents, if indicated, can be used.
GI Decontaminants
Used to limit amount of adsorbed toxin.
Activated charcoal (Liqui-Char)
Emergency treatment in poisoning caused by drugs and chemicals. Network of pores present in activated charcoal adsorbs 100-1000 mg of drug per gram of charcoal. Does not dissolve in water.
For maximum effect, administer within 30 min after ingesting poison.
Adult
0.5-1 g/kg PO/NG (50-100 g); no cathartic (eg, 70% sorbitol) should be given.
Pediatric
0.5-1 g/kg PO/NG (15-50 g)
May inactivate ipecac syrup if used concomitantly; effectiveness of other medications decrease with coadministration; do not mix charcoal with sherbet, milk, or ice cream (decreases adsorptive properties of activated charcoal)
Documented hypersensitivity; poisoning or overdosage of mineral acids and alkalies; unprotected airway with absent gag reflex
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
Not very effective in poisonings of ethanol, methanol, and iron salts; induce emesis before giving activated charcoal; after emesis with ipecac, patient may not tolerate activated charcoal for 1-2 h; can administer in early stages of gastric lavage; without sorbitol, gastric lavage returns are black; may require NG tube for administration; may require ET intubation to control airway and prevent aspiration
Antiemetics
Useful in treatment of symptomatic nausea. Consider risks or benefits of increased sedation and possibility of lowering seizure threshold.
Ondansetron (Zofran)
Selective 5-HT3-receptor antagonist that blocks serotonin both peripherally and centrally.
Adult
4-12 mg IV q8h prn nausea
Pediatric
<1 month: Not established
>1 month:
<40 kg: 0.1 mg/kg (up to 40 mg) q6h prn nausea
>40 kg: 4 mg IV q6h prn nausea
Although there is potential for cytochrome P-450 inducers (barbiturates, rifampin, carbamazepine, and phenytoin) to change half-life and clearance of ondansetron, dosage adjustment is not usually required
Documented hypersensitivity
Pregnancy
B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
Precautions
May cause headache; ondansetron may lead to dose-dependent increase in PR, QRS duration, QT/QTc or JT (caution in patients with known prolonged QT or congenital long QT syndrome)
Metoclopramide (Reglan)
Works as antiemetic by blocking dopamine receptors in the chemoreceptor trigger zone of CNS.
Adult
0.4-1 mg/kg IV (10-20 mg IV) q6-8h
Pediatric
<6 years: 0.1 mg/kg IV slowly over 1-2 min
>6 years: Administer as in adults
Anticholinergics may antagonize effects; opiate analgesics may increase toxicity in CNS; increases rate of absorption of ethanol; may not be effective in patients receiving levodopa; neuromuscular blocking effects of succinylcholine may be increased, producing prolonged respiratory depression and apnea; zalcitabine bioavailability is mildly reduced when coadministered; preanesthetic use may increase frequency and severity of neuromuscular excitation and hypotension when coadministered with thiopental; coadministration with fosfomycin lowers concentrations and urinary excretion of fosfomycin
Documented hypersensitivity; pheochromocytoma or GI hemorrhage, obstruction, or perforation; history of seizure disorders
Pregnancy
B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
Precautions
Caution in history of mental illness and Parkinson disease; observe for tardive dyskinesia and extrapyramidal effects
Benzodiazepines
Can be used to control/prevent seizures and may decrease agitation. Rapid onset of action is advantageous, as is their improved safety profile vs barbiturates.
Diazepam (Valium)
Depresses all levels of CNS (eg, limbic and reticular formation), possibly by increasing activity of GABA.
Adult
0.2 mg/kg IV at 2 mg/min, not to exceed 20 mg/dose; may repeat, monitor for respiratory depression
Pediatric
0.2-0.5 mg/kg IV
<5 years: Not to exceed 5 mg
>5 years: Not to exceed 10 mg
Increases toxicity of benzodiazepines in CNS with coadministration of phenothiazines, barbiturates, cimetidine, ethanol, disulfiram, and MAOIs
Documented hypersensitivity; altered mental status; low BP or RR; narrow-angle glaucoma
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); caution in altered mental status, respiratory depression, and hypotension
Lorazepam (Ativan)
Sedative hypnotic with short onset of effects and relatively long half-life.
Increasing action of GABA, which is a major inhibitory neurotransmitter in the brain, may depress all levels of CNS, including limbic and reticular formation.
Monitoring patient's blood pressure after administering dose is important. Adjust prn.
Lorazepam contains benzyl alcohol, which may be toxic to infants in high doses.
Adult
0.044 mg/kg (2-4 mg) IV, titrate to desired effect
Status epilepticus: 4 mg IV over 2-5 min; may repeat second dose in 10-15 min prn; not to exceed 8 mg
Pediatric
Neonates: 0.05 mg/kg IV over 2-5 min; may repeat in 10-15 min prn
Infants and children: 0.1 mg/kg over 2-5 min; second dose of 0.05 mg/kg IV at 10-15 min prn; single dose not to exceed 4 mg
Children: 0.05 mg/kg IV (0.02-0.1 mg/kg)
Adolescents: Administer as in adults
Status epilepticus: Adolescents receive 0.7 mg/kg (not to exceed 4 mg) given slowly over 2-5 min; second dose at 10-15 min prn
Toxicity of benzodiazepines in CNS increases when used concurrently with alcohol, phenothiazines, barbiturates, and MAOIs
Documented hypersensitivity; preexisting CNS depression; hypotension; narrow-angle glaucoma
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 for respiratory depression with high or repeated doses
Midazolam (Versed)
Used as alternative in termination of refractory status epilepticus. Because water soluble, takes approximately three times longer than diazepam to peak EEG effects. Thus, the clinician must wait 2-3 min to fully evaluate sedative effects before initiating procedure or repeating dose. Has twice the affinity for benzodiazepine receptors than diazepam. May be administered IM if unable to obtain vascular access.
Adult
0.01-0.05 mg/kg (usually 0.5-4 mg, up to 10 mg) IV given slowly over several min; may repeat q10-15min until adequate response achieved
Pediatric
<32 weeks: 0.5 mcg/kg/min IV infusion
>32 weeks: 1 mcg/kg/min IV infusion
Children: 0.05-0.2 mg/kg IV over 2-3 min, followed by 1-2 mcg/kg/min continuous infusion
Status epilepticus (refractory to standard therapy), >2 months and children: 0.15 mg/kg followed by continuous infusion of 1 mcg/kg/min, titrating dose upward q5min until seizures controlled
Sedative effects may be antagonized by theophyllines; narcotics, cimetidine, ethanol, and erythromycin may accentuate sedative effects due to decreased clearance; reduce dose of thiopental by 15% when using together
Documented hypersensitivity, sensitivity to propylene glycol (the diluent); preexisting hypotension; narrow-angle glaucoma
Pregnancy
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Precautions
Caution in congestive heart failure, pulmonary disease, renal impairment, hepatic failure, neuromuscular disease, hypotension, and patients >60 y; monitor for respiratory depression with high or repeated doses; consider lower dosages in patients with organic brain syndrome and patients who may have inhibition of benzodiazepine metabolism and clearance (eg, use of nicotine or taking cimetidine)
Barbiturates
Can be used to control/prevent seizures and may decrease agitation. Rapid onset of action is advantageous.
Phenobarbital (Barbita, Luminal, Solfoton)
Can be administered orally; in status epilepticus, it is important to achieve therapeutic levels as quickly as possible. IV dose may require approximately 15 min to attain peak levels in the brain. If injected continuously until convulsions stop, brain concentrations may continue to rise and can exceed that required to control seizures. Important to use minimal amount required and wait for anticonvulsant effect to develop before giving a second dose.
If IM route chosen, administer into areas with little risk of encountering a nerve trunk or major artery such as one of large muscles like gluteus maximus, vastus lateralis, or other. Permanent neurological deficit may result from injecting into or near peripheral nerves.
Restrict IV use to conditions in which other routes are not possible, either because patient is unconscious or because prompt action is required.
Adult
10-20 mg/kg IV administered <50 mg/min
Pediatric
15-20 mg/kg IV administered <50 mg/min
May decrease effects of chloramphenicol, digitoxin, corticosteroids, carbamazepine, theophylline, verapamil, metronidazole, and anticoagulants (patients stabilized on anticoagulants may require dosage adjustments if added to or withdrawn from their regimen); coadministration with alcohol may produce additive CNS effects and death; chloramphenicol, valproic acid, and MAOIs may increase phenobarbital toxicity; rifampin may decrease phenobarbital effects; induction of microsomal enzymes may result in decreased effects of oral contraceptives in women (must use additional contraceptive methods to prevent unwanted pregnancy; menstrual irregularities may also occur)
Documented hypersensitivity; severe respiratory disease; marked impairment of liver function, nephritis
Pregnancy
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Precautions
In prolonged therapy, evaluate hematopoietic, renal, hepatic, and other organ systems; caution in fever, hyperthyroidism, diabetes mellitus, and severe anemia since adverse reactions can occur; caution in myasthenia gravis and myxedema; monitor for hypotension, respiratory depression, and need for intubation
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| Differential Diagnoses & Workup: Plant Poisoning, Hemlock |
 Treatment & Medication: Plant Poisoning, Hemlock |
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| Multimedia: Plant Poisoning, Hemlock |
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References
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Further Reading
Keywords
hemlock, plant poison hemlock, poison hemlock, Conium maculatum, C maculatum, water hemlock, Cicuta maculata, C maculata, plant ingestion, Queen Anne's lace, wild carrot, fool's parsley
