0071643192.pdf

TOXICOLOGY

SYMPTOMS/EXAM

■ Nausea and vomiting

■ Slurred speech, ataxia, depressed mental status, and seizures

■ The classic presentation is persistent seizures and resultant metabolic

acidosis.

DIAGNOSIS

■ Should be suspected in any patient with seizures who is undergoing

treatment for TB or is refractory to standard treatment

■ INH levels take too long to be clinically useful in the ED.

TREATMENT

■ Supportive care

■ Activated charcoal if early and no CNS depression

■ Benzodiazepines for status epilepticus until antidote available

■ Antidote: Pyridoxine (vitamin B 6 )replenishes vitamin B 6 stores to help

replete GABA.

COMPLICATIONS

■ Chronic large doses of pyridoxine may cause peripheral neuropathy.

Reverse Transcriptase Inhibitors

Reverse transcriptase inhibitors are antiretroviral agents used in the treatment

of HIV. Highly active antiretroviral therapy (HAART) refers to a drug regimen

combining reverse transcriptase inhibitors with agents from two other anti-

retroviral classes, protease inhibitors and fusion inhibitors.

Reverse transcriptase inhibitors include didanosine (ddI), stavudine (d4T),

lamivudine (3TC), and others.

MECHANISM/TOXICITY

■ Mitochondrial toxicity →lactic acidosis, hepatotoxicity, pancreatitis.

SYMPTOMS/EXAM

■ Malaise

■ Tachypnea

■ N/V, abdominal pain

DIAGNOSIS

■ Suspect based on clinical presentation.

■ Confirmed with laboratory findings (elevated lactate, etc.)

■ Muscle or liver biopsy is definitive for diagnosis of mitochondrial toxicity.

TREATMENT

■ Discontinue implicated drug(s).

■ Supportive care

■ If severe lactic acidosis →sodium bicarbonate

■ Hemodialysis may be considered.

INH is listed as a cause of an

anion gap metabolic acidosis

because it causes a profound

lactic acidosis from seizure

activity. It does not cause

lactic acidosis when seizures

are not present.

Reverse transcriptase

inhibitors may cause a

profound lactic acidosis due to

mitochondrial toxicity.