USMLE USMLE Certifications USMLE-STEP-1 Questions & Answers

• Question 181:

  Apatient has been treated for bipolar disorder for several months. Which of the following is a common adverse effect of lithium carbonate?

  A. dry mouth

  B. hyperthyroidism

  C. leucopenia

  D. nephrogenic diabetes insipidus

  E. parkinsonian extrapyramidal symptoms

  Correct Answer: D

  Section: Pharmacology Nephrogenic diabetes insipidus is a common adverse effect of lithium at therapeutic dosage. Dry mouth (choice A) and other anticholinergic toxicities are common with tricyclic antidepressants and some phenothiazines. Lithium may induce hypothyroidism, but not hyperthyroidism (choice B). Similarly, lithium increases rather than decreases white blood cell count (choice C). Finally, lithium often causes tremor, but not parkinsonism (choice E).

• Question 182:

  Which of the following drugs is most dangerous in suicidal overdosage?

  A. bupropion

  B. citalopram

  C. fluoxetine

  D. imipramine

  E. phenelzine

  Correct Answer: D

  Section: Pharmacology Imipramine and other tricyclics are the most dangerous antidepressants when taken in overdosage because of their cardiotoxic (arrhythmias) and neurologic (seizures) effects. Bupropion (choice A), the selective serotonin reuptake inhibitors (SSRIs) (choices B and C), and MAO inhibitors (choice E) are considerably less dangerous.

• Question 183:

  A 35-year-old man has severe schizophrenia. He is institutionalized and maintained on antipsychotic medication. Which of the following drugs is most likely to cause parkinsonian adverse effects?

  A. clozapine

  B. fluphenazine

  C. haloperidol

  D. olanzapine

  E. quetiapine

  Correct Answer: C

  Section: Pharmacology Haloperidol is a very potent and efficacious antipsychotic but also manifests the highest incidence of extrapyramidal effects. Clozapine (choice A), olanzapine (choice D), and quetiapine (choice E) are newer, atypical antipsychotic agents with much lower incidence of extrapyramidal toxicity. Fluphenazine (choice B) is a potent phenothiazine with an intermediate tendency to produce parkinson- like effects.

• Question 184:

  A 26-year-old woman with cerebral palsy complains of severe pain associated with spasms in her leg muscles. Which of the following drugs is used in cerebral palsy to reduce skeletal muscle spasticity by an action on cholinergic nerve endings?

  A. baclofen

  B. botulinum toxin

  C. dantrolene

  D. diazepam

  E. tubocurarine

  Correct Answer: B

• Question 185:

  Which of the following is the only local anesthetic that causes vasoconstriction and may result in an increase in blood pressure?

  A. bupivacaine

  B. cocaine

  C. etidocaine

  D. lidocaine

  E. tetracaine

  Correct Answer: B

  Section: Pharmacology Cocaine is the only local anesthetic that causes sympathomimetic effects (by inhibiting reuptake of norepinephrine into sympathetic nerve endings); it therefore regularly causes local vasoconstriction and may increase blood pressure. All the other local anesthetics (choices A, CE) cause vasodilation and lower blood pressure.

• Question 186:

  Which of the following agents used in general anesthesia is least likely to cause postoperative nausea and vomiting?

  A. enflurane

  B. etomidate

  C. isoflurane

  D. morphine

  E. propofol

  Correct Answer: E

  Section: Pharmacology Propofol may reduce blood pressure through vasodilating and negative inotropic effects on the heart, but is notable for rapid recovery and its freedom from postoperative nausea and vomiting. For this reason, it is extremely popular for day surgery. None of the other anesthetics (choices AD) are free from causing postoperative nausea.

• Question 187:

  A 70-year-old man presents with Parkinson's disease in an early stage. Which of the following drugs acts directly on dopamine receptors to reduce the signs and symptoms of Parkinson's disease?

  A. amantadine

  B. carbidopa

  C. entacapone

  D. orphenadrine

  E. pramipexole

  Correct Answer: E

  Section: Pharmacology Pramipexole is a dopamine receptor agonist unrelated to levodopa or ergot derivatives such as bromocriptine and pergolide (which are also useful dopamine agonists). Amantadine (choice A) acts to facilitate the release or slow the reuptake of dopamine, but does not act on the dopamine receptor. Carbidopa (choice B) blocks the peripheral conversion of levodopa to dopamine, it does not act on dopamine receptors. Entacapone (choice C) blocks the peripheral metabolism of levodopa by catechol- Omethyltransferase. Orphenadrine (choice D) is a centrally acting anticholinergic agent that is sometimes used in Parkinson's disease.

• Question 188:

  A child with absence seizures is being evaluated for therapy with ethosuximide. Which of the following is the most common adverse effect of ethosuximide in children?

  A. hemolytic anemia

  B. excessive sedation

  C. hepatic necrosis

  D. nephropathy

  E. torsade de pointe arrhythmia

  Correct Answer: B

  Section: Pharmacology Ethosuximide is usually a very safe drug, but can cause significant sedation. Aplastic anemia but not hemolytic anemia (choice A) has rarely been associated with the use of ethosuximide, and with carbamazepine and felbamate. Hepatotoxicity (choice C) is a rare but potentially lethal adverse effect of valproic acid that occurs most commonly in children under the age of 2 and those taking multiple drugs. Authorities recommend monitoring liver function tests when starting this drug. Nephropathy (choice D) is not usually reported with antiseizure drugs. Torsade de pointe arrhythmia (choice E) has not occurred with significant frequency during use of anticonvulsant drugs.

• Question 189:

  Zolpidem is a newer sedative-hypnotic drug approved for use as a sleeping pill. Which of the following statements describes the major difference between zolpidem and older hypnotics such as barbiturates and benzodiazepines?

  A. associated with thrombocytopenia

  B. does not act on chloride channels in the CNS

  C. has significant anticonvulsant activity

  D. much longer duration of action

  E. reduced addiction liability

  Correct Answer: E

  Section: Pharmacology Zolpidem has greatly reduced addiction liability compared to barbiturates and benzodiazepines even though it does act on chloride channels (choice B). Zolpidem does not have major anticonvulsant actions (choice C), a longer duration of action (choice D), or thrombocytopenic toxicity (choice A).

• Question 190:

  Which of the following drugs is useful in asthma because it stabilizes mast cells?

  A. albuterol

  B. cromolyn

  C. ipratropium

  D. salmeterol

  E. theophylline

  Correct Answer: B

  Section: Pharmacology Cromolyn is a prophylactic agent for asthma that appears to stabilize mast cells. Albuterol A. is a shorter acting beta-2-selective agonist that is used for acute, not prophylactic, therapy. Ipratropium (choice C) is an antimuscarinic drug. Salmeterol D. has a long duration beta-2-agonist action that appears to have an anti- inflammatory action and is useful in prophylaxis of asthmatic attacks. It has a slow onset of action that makes it useless in treating acute attacks. Theophylline (choice E) is an intermediate duration agent that acts by inhibition of phosphodiesterase or adenosine receptors.