Definition: Acute methamphetamine (aka meth) intoxication is a constellation of symptoms caused by illicit or medicinal use of methamphetamines with predominant sympathomimetic clinical effects.
- Amphetamines (of which methamphetamines are a derivative) are the second most common cause of illicit drug use worldwide, behind marijuana (UN 2016)
- Methamphetamines can be used medicinally in the treatment of ADHD, obesity, and narcolepsy, but the majority of overdoses seen will be from the illegally manufactured variety.
- The typical “street dose” for Methamphetamines ranges from 0.1-0.3 grams, depending on the concentration, route of administration and patient tolerance.
- “Crystal” methamphetamine (or “ice”) is a crystalline form that is less likely to be cut with other substances and considered to be a purer form.
- An overdose syndrome occurs when the body begins to have adverse effects from the ingestion of Methamphetamines.
- The etiology of the effects of Methamphetamines is complex, but stems from the release of dopamine, norepinephrine, and serotonin from the presynaptic terminals
|Receptor||Regulatory function||Effects due to meth|
|Norepinephrine||Stimulates sympathetic nervous system||Increased alertness, inotropy, vasoconstriction|
|Serotonin||Mood, memory, temperature regulation, sleep, pain||Hallucinogenic/illusionic properties|
|Dopamine||Reward, motivation, the experience of pleasure, and motor function||Addiction, Drug-seeking behavior, stereotypical movements, psychiatric symptoms.|
Onset of Action
|Mode of ingestion||Onset of action||Peak plasma concentration||Half-life|
|Smoking/injecting||Seconds||30 minutes||10-34 hours|
|Snorting||5 minutes||1.5 hours|
|Eating||20 minutes||2-3 hours.|
Signs + Symptoms:
- Psychomotor Agitation
- Due primarily to serotonergic and dopaminergic effects
- Motor component
- Can range from restlessness to severe muscle spasms. Likely main contributor to hyperthermia.
- Mydriasis – from stimulation of SNS.
- Diaphoresis – From psychomotor agitation
- Psychiatric component
- Methamphetamines are weak MAOI’s. Patients may have methamphetamine toxidrome as well as serotonin syndrome. (Hoffman 2015)
- Critical contributor to morbidity/mortality
- Caused by heat production from psychomotor agitation and, to a lesser degree, from central serotonergic stimulation.
- Cardiovascular effects
- Due primarily to adrenergic stimulation.
- Dysrhythmias – Ranges from tachycardia (common) to ventricular fibrillation (less common)
- Myocardial ischemia/infarction
- Aortic dissection
- Obstetrical complications including placental abruption and fetal death
- Ischemic colitis
- Initial Supportive Measures (focus on airway, breathing and circulation)
- RSI should be performed without the use of succinylcholine because these patients may have elevated potassium due to renal compromise from rhabdomyolysis
- Special attention should be given to the patient’s circulatory status. In the initial stages of intoxication, patients often have elevated BP and HR. However, as their clinical course progresses, they can often have circulatory collapse without warning
- Severe hyperthermia should be rapidly corrected as it can quickly lead to death
- External cooling with ice bath submersion
- Relieve psychomotor agitation
- Can be used as 1st line in mild hyperthermia
- Sinus tachycardia
- Most common dysrhythmia
- 1st line treatment: BZDs
- Other dysrhythmias (ventricular tachycardia, atrial fibrillation) can be treated with standard ACLS approaches
- Sinus tachycardia
- Psychomotor agitation
- Escalating doses of benzodiazepines should be used to suppress agitation
- Mild to moderate toxicity
- Lorazepam 1-2 mg IV
- Diazepam 5-10 mg IV
- Moderate to severe toxicity
- Lorazepam 2-4 mg IV
- Diazepam 10-20 mg IV
- BZD doses can be repeated as needed to control agitation. The time between doses depends on the agent used
- Gastric decontamination may be considered.
- Acute oral ingestion – If mental status appropriate (and no other contraindications), 50 grams activated charcoal within 1-2 hrs of ingestion.
- Body packers – Consider whole bowel irrigation in consultation with your local poison control center (Thanacoody 2015)
Take Home Points
- For the majority of patients, administering supportive care and benzodiazepines is sufficient.
- Hyperthermia from psychomotor agitation is the most common cause of death and disability. Aggressively cool patients, look for rhabdomyolysis and renal failure and treat with IV fluids.