Toxicology

Compound A is reported to have an oral LD50 of 5 mg/kg body weight. Compound B is reported to have an LD50 of 50 mg/kg body weight. Of the following statements regarding the relative toxicity of these two compounds, which is TRUE? a. Ingestion of low amounts of compound A would be predicted to cause more deaths than an equal dose of compound B. b. Ingestion of compound B would be expected to produce nontoxic effects at a dose greater than 100 mg/kg body weight. c. Neither compound A nor compound B is toxic at any level of oral exposure. d. Compound A is more rapidly adsorbed from the gastrointestinal tract than compound B. e. Compound B would be predicted to be more toxic than compound A if the exposure route were transdermal.

Which of the following statements best describes the TD50 of a compound? a. The dosage of a substance that would be predicted to cause a toxic effect in 50% of the population b. The dosage of a substance that is lethal to 50% of the population c. The dosage of a substance that would produce therapeutic benefit in 50% of the population d. The percentage of individuals who would experience a toxic response at 50% of the lethal dose e. The percentage of the population who would experience a toxic response after an oral dosage of 50 mg

Of the following analytic methods, which is most commonly used as the confirmatory method for identification of drugs of abuse? a. GC with mass spectrometry b. Scanning differential calorimetry c. Ion-specific electrode d. Immunoassay e. Nephelometry

. A weakly acidic toxin (pKa = 4.0) that is ingested will a. Be passively absorbed in the stomach (pH = 3.0) b. Not be absorbed because it is ionized c. Not be absorbed unless a specific transporter is present d. Be passively absorbed in the colon (pH = 7.5) e. Be absorbed only if a weak base is ingested at the same time

What is the primary product of methanol metabolism by the ADH and ALDH system? a. Formic acid b. Acetone c. Acetaldehyde d. Oxalic acid e. Formaldehyde

Which of the following statements concerning cyanide toxicity is TRUE? a. Inhalation of smoke from burning plastic is a common cause of cyanide exposure, and cyanide expresses its toxicity by inhibition of oxidative phosphorylation. b. Inhalation of smoke from burning plastic is a common cause of cyanide exposure. c. Cyanide is a relatively nontoxic compound that requires chronic exposure to produce a toxic effect. d. Cyanide expresses its toxicity by inhibition of oxidative phosphorylation. e. All of these are true.

Which of the following laboratory results would be consistent with acute high-level oral exposure to an inorganic form of mercury (Hg2+)? a. All of these b. High concentrations of mercury in whole blood and urine c. Proteinuria d. Positive occult blood in stool e. None of these

• A child presents with microcytic, hypochromic anemia. The physician suspects iron deficiency anemia. Further laboratory testing reveals a normal total serum iron and iron-binding capacity; however, the zinc protoporphyrin level was very high. A urinary screen for porphyrins was positive. Erythrocytic basophilic stippling was noted on the peripheral smear. Which of the following laboratory tests would be best applied to this case? a. Whole blood lead b. Urinary thiocyanate c. COHb d. Urinary anabolic steroids e. Urinary benzoylecgonine

A patient with suspected organophosphate poisoning presents with a low SChE level. However, the confirmatory test, erythrocyte acetylcholinesterase, presents with a normal result. Excluding analytic error, which of the following may explain these conflicting results? a. The patient has late-stage hepatic cirrhosis or the patient has a variant of SChE that displays low activity. b. The patient has late-stage hepatic cirrhosis. c. The patient was exposed to low levels of organophosphates. d. The patient has a variant of SChE that displays low activity. e. All of these are correct.

A patient enters the emergency department in a coma. The physician suspects a drug overdose. Immunoassay screening tests for opiates, barbiturates, benzodiazepines, THC, amphetamines, and PCP were all negative. No ethanol was detected in serum. Can the physician rule out drug overdose as the cause of this coma with these results? a. No b. Yes c. Maybe