Review Question - QID 217784

This patient who presents with behavior change (increased anger and outbursts) and weight loss is likely using cocaine. The mechanism of action of cocaine is through the inhibition of dopamine and catecholamine reuptake.

Cocaine functions by blocking biogenic amine (dopamine, norepinephrine, and serotonin) reuptake. Increased levels of dopamine in the reward circuits of the brain lead to cocaine's effects. Signs of cocaine use include mental status and behavior changes. This may manifest as euphoria, psychomotor agitation, anger, grandiosity, and paranoia. Increased levels of catecholamines lead to activation of the sympathetic nervous system, leading to decreased appetite, tachycardia, hypertension, pupillary dilation, diaphoresis, and angina. Chronic cocaine use can lead to changes such as weight loss and erythema of the turbinates/septum. In severe cases, perforation of the nasal septum can occur due to vasospasm of the Kiesselbach plexus. Treatment for acute cocaine use is usually supportive, though antipsychotics and benzodiazepines may be used in select cases. Chronic cocaine users are treated with supportive care and resources to assist in cessation.

Nestler et al. discuss the neurobiology of cocaine and the mechanisms by which using cocaine can lead to addiction. They found that although the drug increases levels of norepinephrine and serotonin, it is the increase of dopamine levels that has been most linked to addiction. They recommend further research into the effects of the transcription factor ΔFosB as a potential way to treat cocaine addiction.

Incorrect Answers:
Answer 1: Gamma-aminobutyric acid receptor agonism is the mechanism of action of alcohol and benzodiazepines. Intoxication with these substances leads to disinhibition, somnolence, ataxia, slurred speech, and emotional lability.

Answer 3: Inhibition of dopamine breakdown is the mechanism of action of drugs such as selegiline and rasagiline. These drugs inhibit the enzyme monoamine oxidase, which is responsible for the metabolism of dopamine. These drugs are typically used as adjunctive agents along with levodopa in the treatment of Parkinson disease.

Answer 4: Inhibition of serotonin reuptake is the mechanism of action of selective serotonin reuptake inhibitors (SSRIs). SSRIs may be used in the treatment of major depressive disorder and anxiety disorders. Overdose of SSRIs can lead to serotonin syndrome, which presents with agitation, autonomic dysfunction, hyperreflexia, and restlessness.

Answer 5: N-methyl-D-aspartate receptor antagonism is the mechanism of action of phencyclidine (PCP). PCP use presents with belligerence, impulsiveness, psychosis, delirium, seizures, psychomotor agitation, tachycardia, and ataxia.

Bullet Summary:
Cocaine's mechanism of action is through the blockade of the reuptake of dopamine, serotonin, and catecholamines.