Repeated USMLE Questions Step 1- Review- 55- Pharmacology

Q- Which one of the following substances can cause decrease in blood pressure through stimulation of non-innervated muscarinic receptors present on arterioles?

A- Acetylcholine

B- Atropine

C- Norepinephrine

D- Phentolamine

A- Acetylcholine- This is the only one on the list that stimulates the muscarinic receptors present on the arterioles.

Q- Legionnaires disease is caused by infection with a small gram-negative Legionella pneumophila through inhalation of infected air coming out of air conditions. Which of the following is the treatment of choice of this condition?

A- Ampicillin and gentamicin

B- Ceftriaxone and clindamycin

C- Levofloxacin and azithromycin

D- Trimethoprim-sulfamethoxazole

C- Levofloxacin and azithromycin- These antibiotics are able to achieve high lung tissue concentration and they have long half-lives so; they are the most appropriate to treat legionella pneumonia.

Q- A drug with renal clearance of 20 ml/min was given to a patient. This drug is 30% plasma protein bound and the GFR of this patient is 120 ml/min. Which of the following is the amount of filtered drug reabsorbed in the collecting tubules?

A- 20 ml/min

B- 64 ml/min

C- 84 ml/min

D- 120 ml/min

B- 64 ml/min- Free drug (ff) is 70%. Cl = ff x GFR so Cl is 120 x 70% = 84 which is the theoretical clearance of the drug. Since only 20 ml is actually cleared of the drug/min so, the amount was reabsorbed is 84-20 = 64

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