Jan 27, 2003: What are the actions of methamphetamine?

Amphetamines selectively enhance the release of dopamine and norepinephrine and block the reuptake of these catecholamines at the synapse. The marked increase in dopamine level may be related to the “high”.   There is increase of α and β receptors stimulation.  Increased norepinephrine in the locus cereleus causes anorexia, increased alertness, and locomotor stimulation. 

The legal methamphetamines i.e., drugs used for the treatment of ADD and narcolepsy are administered in much lower dose than addressed here.  At very low dose, the psychostimulant methamphetamine has a paradoxical calming effect.   

Amphetamines cause a sense of euphoria accompanied by increased energy, decreased fatigue, and enhanced self-confidence.  Acute effects may last 4 to 24 hours. 

Side effects include bruxism, anorexia, myalgia, and ataxia.  Hangovers occur accompanied by jaw aching.  Panic attacks and chronic paranoid psychosis may develop with continued use.   

Pharmacokinetically, the drug is very lipophilic.  Half-life is 8-30 hours.  The drug is hepatically metabolized with renal elimination.  

In overdose, sympathetic effects predominate-life-threatening hyperthermia, coma, seizures, hypertension, and cardiovascular collapse are causes of death.  Agitation, bruxism, muscle rigidity, diaphoresis, hypertension, tachycardia, leukemoid reaction, DIC, and rhabdomyolysis occur.   

Treatment is supportive.  High temperatures should be treated aggressively.  Dantrolene administration may be considered.  Benzodiazepines should be administered for seizures.

Next week: Does methamphetamine abuse cause long-term neurotoxicity?

As always, if there are any questions, call the MTPC.

I am interested in any questions that you would like answered in “Question of the Week.”  Please e-mail me with any suggestions at donna.seger@Vanderbilt.edu

Donna Seger, M.D.
Medical Director, Middle Tennessee Poison Center