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USMLE Step 1 Pharmacology

Subjects : health-sciences, usmle-step-1

Instructions:

Answer 50 questions in 15 minutes.
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Match each statement with the correct term.
Don't refresh. All questions and answers are randomly picked and ordered every time you load a test.

This is a study tool. The 3 wrong answers for each question are randomly chosen from answers to other questions. So, you might find at times the answers obvious, but you will see it re-enforces your understanding as you take the test each time.

1. What is the possible mechanism and effect of Metformin in treating diabetes?
Inhibits bacterial Dihydrofolate Reductase - Bacteriostatic
Milk or Antacids - because divalent cations inhibit Tetracycline absorption in the gut
Mechanism unknown; possibly inhibits gluconeogenesis and increases glycolysis; effect is to decrease serum glucose levels
Inhibits NaCl reabsorption in the early distal tubule. Decreases Ca2+ excretion.

2. Adverse effects of Methyldopa?

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3. Spironolactone - mechanism?
- Fluoroquinolones
Abortifacient.
competitive inhibirot of aldosterone in the cortical collecting tubule
- Tetracycline - amiodarone - sulfonamides

4. Why is pyridostigmine effective in the treatment of myasthenia gravis?
- Act on same receptor - Full has greater efficacy
H2 antagonist
It affects beta receptors equally and is used in AV heart block (rare).
As an anticholinesterase it increases endogenous ACh and thus increases strength.

5. What are two mechanisms of action of Propythiouracil?
Protamine Sulfate is used for rapid reversal of heparinization (positively charged molecule that binds to negatively charged heparin).
Inhibits organification and coupling of thyroid hormone synthesis. Also decreases peripheral conversion of T4 to T3.
Pseudomonas species and Gram - rods
Modification via Acetylation

6. What is the category of drug names ending in - ane (e.g. Halothane)
Penicillin - Cephalosporins - Vancomycin - Aminoglycosides - Fluoroquinolones - Metronidazole
- Class III antiarrhythmics (sotalol) - class IA (quinidine)
Flecainide - Encainide - Propafenone
Inhalational general anesthetic.

7. Resistance mechanisms for Tetracycline
blocking the beta adrenergic receptor leads to decreased cAMP - and decreased Ca2+ flux
Decreased uptake or Increased transport out of cell
- Physostigmine salicylate
- Vitamin K & fresh frozen plasma

8. What are Amantadine - associated side effects?
Gentamicin - Neomycin - Amikacin - Tobramycin - Streptomycin
Nephrotoxicity (esp. with Cephalosporins) - Ototoxicity (esp. with Loop Diuretics)
Ataxia - Dizziness - Slurred speech
impotence - exacerbation of asthma - CV effects - CNS effects - may mask hypoclycemia

9. What are three common NSAIDS other than Aspirin?
Rare.
- Tricyclic antidepressants
Rash - Pseudomembranous colitis
Ibuprofen - Naproxen - and Indomethacin

10. Why would you use pralidoxime after exposure to an organophosphate?
Cephalosporin: 1) has a 6 member ring attached to the Beta lactam instead of a 5 member ring 2)has an extra functional group ( attached to the 6 member ring)
Antibiotic - protein synthesis inhibitor.
Ipratropium
Pralidoxime regenerates active cholinesterase.

11. Aztreonam ________ to penicillinase
Hypokalemic metabolic alkalosis - hyponatremia - hyperGlycemia - hyperLipidemia - hyperUricemia - hyperCalcemia - sulfa allergy.
Because they require some residual islet function.
is resistant
anticholinesterase glaucoma

12. List the mechanism - clinical use - & toxicity of Cyclophosphamide.
Gram + cocci - Proteus mirabilis - E. coli - Klebsiella pneumoniae (PEcK)
Penicillin.
No
- Alkalating agent - NHL - Breast - ovary - & lung. - Myelosuppression - & hemorrhagic cystitis.

13. Amiodarone - toxicity?
Md= (CpxCL)/F Cp= plas. Conc. CL=clear. F=bioaval.
Binds ergosterol - Disrupts fungal membranes
pulmonary fibrosis - corneal deposits - hepatotoxicity - skin deposits resulting in photodermatitis - neurologic effects - consitpation - CV (bradycardia - heart block - CHF) - and hypo - or hyperthyroidism.
- Isoniazid

14. What is the MOA for Metronidazole?
Forms toxic metabolites in the bacterial cell - Bactericidal
IV vitamin K and fresh frozen plasma
Initially vasoconstriction would increase bp - but then it acts on central alpha -2 receptors to decrease adrenergic outflow resulting in decreased bp.
Nucleosides

15. What are the products and their toxicities of the metabolism of Methanol by / alcohol dehydrogenase?
- Formaldehyde & formic acid - severe acidosis & retinal damage
hypertrichosis - pericardial effusion - reflex tachycardia - angina - salt retention
Ganciclovir is more toxic to host enzymes
- Quinidine - quinine

16. What is Fluconazole specifically used for?
Blocks viral penetration/uncoating; may act to buffer the pH of the endosome
1) Serious Gram - infections resistant to other Beta lactams 2) Meningitis (most penetrate the BBB)
With supplemental Folic Acid
Cryptococcal meningitis in AIDS patients and Candidal infections of all types

17. What type of gout is treated with Allopurinol?
Disulfiram - like reaction with EtOH - Headache
- Methylene blue
- Vinca alkaloids(inhibit MT) - Paclitaxel
Chronic gout.

18. What are two toxicities of the Glitazones?
Intrathecally
Nonspecific beta - agonist; desired effect is the relaxation of bronchial smooth muscle (Beta 2). Adverse effect is tachycardia (Beta 1).
collecting ducts
1. Weight gain 2. Hepatotoxicity (troglitazone)

19. Verapamil has similar action to?
Staphlococcus aureus and Clostridium difficile (pseudomembranous colitis)
Beta Blockers
CMV Retinitis in IC pts When Ganciclovir fails
Blocks Peptide Bond formation at the 50S subunit - Bacteriostatic

20. What is the MOA of the RT Inhibitors?
Gram + - Gram - - Norcardia - Chlamydia
Oral treatment of superficial infections
Inhibit RT of HIV and prevent the incorporation of viral genome into the host DNA
YES

21. Which drug(s) cause this reaction: P450 induction(6)?
edrophonium (extremely short acting anticholinesterase)
- inhibits HGPRT (pur. Syn.) - Luk - Lymph
- Barbiturates - phenytoin - carbamazipine - rifampin - griseofulvin - quinidine
- ACE inhibitors (Losartan>no cough)

22. What is the loading dose formula?
Wide spectrum of systemic mycoses: Cryptococcus - Blastomyces - Coccidioides - Aspergillus - Histoplasma - Candida - Mucor
Milk or Antacids - because divalent cations inhibit Tetracycline absorption in the gut
Nitrates
Ld= (CpxVd)/F Cp=plasma conc. F= Bioaval.

23. How can the toxic effects of TMP be ameliorated?
Those patients who are taking nitrates.
Finasteride inhibits 5 Alpha - reductase - this decreases the conversion of testosterone to dihydrotestosterone - useful in BPH
GI distress - Tooth discoloration and Inhibition of bone growth in children - Fanconi's syndrome - Photosensitivity
With supplemental Folic Acid

24. Toxic side effects of the Azoles?
Hormone synthesis inhibition (Gynecomastia) - Liver dysfunction (Inhibits CYP450) - Fever - Chills
Pralidoxime regenerates active cholinesterase.
Prevents the release of ACh - Which results in muscle paralysis.
fetal renal toxicity - hyperkalemia

25. List the mechanism - clinical use - & toxicity of Paclitaxel.
- Tetracycline - amiodarone - sulfonamides
- MT polymerization stabilizer - Ovarian & breast CA - Myelosupperession & hypersensitivity.
impotence - asthma - CV effects (bradycardia - CHF - AV block) - CNS effects (sedation - sleep alterations)
severe hypertension - CHF

26. What should not be taken with Tetracyclines? / Why?
It must be Phosphorylated by Viral Thymidine Kinase
1. Hot flashes 2. Ovarian enlargement 3. Multiple simultaneous pregnancies 4. Visual disturbances
Milk or Antacids - because divalent cations inhibit Tetracycline absorption in the gut
cardiac muscle: Verapamil>Diltiazem>Nifedipine

27. What microorganisms are Aminoglycosides ineffective against?
reduce levels of Angiotensin II - thereby preventing the inactivation of bradykinin (a potent vasodilator); renin level is increased
Systemic mycoses
Epinephrine
Anaerobes

28. Which Tetracycline is used in patients with renal failure? / Why?
- Alkalinize urine & dialysis
Doxycycline - because it is fecally eliminated
Decrease the production of leukotrienes and protaglandins by inhibiting phospholipase A2 and expression of COX-2.
Enterobacter

29. How do spare receptors effect the Km?
Dobutamine has more of an affintiy for beta -1 than beta -2 - and is used for treating heart failure and shock. Albuterol and terbutaline is the reverse - and is used in treatment of acute asthma.
- ED 50 is less than the Km (less than 50% of receptors)
- DNA intercalator - testicular & lymphomas - Pulmonary fibrosis mild myelosuppression.
Aplastic anemia (dose independent) - Gray Baby Syndrome

30. Specifically - How does Foscarnet inhibit viral DNA pol?
distal convoluted tubule (early)
Binds to the Pyrophosphate Binding Site of the enzyme
Binds to cyclophilins (peptidyl proline cis - trans isomerase) - blocking the differentiation and activation of T cells mainly by inhibiting the production of IL-2 and its receptor.
Prevents the release of Ca from SR of skeletal muscle

31. Which drug(s) cause this reaction: Cough?
- DNA intercalator - testicular & lymphomas - Pulmonary fibrosis mild myelosuppression.
Close K+ channels in Beta - cell membrane leading to cell depolarization causing insulin release triggered by increase in Calcium ion influx.
- ACE inhibitors (Losartan>no cough)
compensatory tachycardia - fluid retention - lupus - like syndrome

32. Which drug(s) cause this reaction: P450 inhibition(6)?
Theoretically it could be used to block the cephalic phase of acid secretion (vagal stimulation).
Protamine Sulfate is used for rapid reversal of heparinization (positively charged molecule that binds to negatively charged heparin).
Suramin
- Cimetidine - ketoconazole - grapefruit juice - erythromycin - INH - sulfonamides

33. List the mechanism - clinical use - & toxicity of Prednisone.

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34. List the mechanism - clinical use - & toxicity of Nitrosureas.
G6PD deficient individuals
- Alkalate DNA - Brain tumors - CNS toxicity
Beta adrenergic receptors and Ca2+ channels (stimulatory)
Used in combination therapy with SMZ to sequentially block folate synthesis

35. Furosemide - class and mechanism?
INH: Injures Neurons and Hepatocytes
- Antipsychotics
Sulfonamide Loop Diuretic. Inhibits ion co - transport system of thick ascending loop. Abolishes hypertonicity of the medulla - thereby preventing concentration of the urine.
Due to the presence of a bulkier R group

36. A group of pts are rushed into the ER complaining of excessive sweating - tearing - salivation - HA - N and V - muscle twitching - difficulty breathing and diarrhea. What drug would be the most effective immediate tx
- Bleomycin - amiodarone - busulfan
Atropine pts are suffering from Cholinestrase inhibitor poisining (Nerve gas/Organophosphate poisining)
Penicillin - V
Immediate anticoagulation for PE - stroke - angina - MI - DVT.

37. Which drug(s) cause this reaction: Extrapyramidal side effects (3)?
check PFTs - LFTs - and TFTs
GET on the Metro
- Chlorpromazine - thioridazine - haloperidol
Hypersensitivity reactions

38. What is the mechanism of action of Aspirin?
AZT - to reduce risk of Fetal Transmission
Ipratropium
Acetylates and irreversibly inhibits cyclooxygenase (COX I and COX II) to prevent the conversion of arachidonic acid to prostaglandins.
1. Infertility (pulsatile) 2. Prostate cancer (continuous: use with flutamide) 3. Uterine fibroids

39. What are two indirect acting adrenergic agonists?
decrease the slope of phase 4 - increase PR interval (the AV node is particularly sensitive)
- Glucocorticoid withdrawal
block voltage dependent L- type Ca2+ channels of cardiac and smooth muscle - decreasing contractility
amphetamine and ephedrine

40. What is the formula for Volume of distribution (Vd)
Giant Roundworm (Ascaris) - Hookworm (Necator/Ancylostoma) - Pinworm (Enterobius)
Vd= (Amt. of drug in body/ Plasma drug conc.)
cardiac muscle: Verapamil>Diltiazem>Nifedipine
Ototoxicity - Hypokalemia - Dehydration - Allergy (sulfa) - Nephritis (interstitial) - Gout

41. What are the major structural differences between Penicillin and Cephalosporin?
Cephalosporin: 1) has a 6 member ring attached to the Beta lactam instead of a 5 member ring 2)has an extra functional group ( attached to the 6 member ring)
Penicillin - G
Cyclooxygenases (COX I - COX II).
Leukotrienes increasing bronchial tone.

42. Describe Phase I metabolism in liver(3)?
Penicillin.
- Ammonium Chloride
- reduction - oxy - & hydrolysis - H2O sol. Polar product - P450
No. Atropine is used to reduce urgency in mild cystitis. So it would aggravate the urinary retention.

43. What are the side effects of Polymyxins?
Edrophonium
Heparin catalyzes the activation of antithrombin III.
Neurotoxicity - Acute renal tubular necrosis
Acute (hours)

44. What can result due to antacid overuse?
1. Kidney transplantation 2. Autoimmune disorders (including glomerulonephritis and hemolytic anemia)
Md= (CpxCL)/F Cp= plas. Conc. CL=clear. F=bioaval.
Can affect absorption - bioavailability - or urinary excretion of other drugs by altering gastric and urinary pH or by delaying gastric emptying.
Stimulating beta receptors stimulates heart rate - but beta receptor induced vasodilation reduces peripheral resistance.

45. What is the MOA for Vancomycin?
1. Predisposes to viral infections and lymphoma 2. Nephrotoxic (preventable with mannitol diuresis)
narcolepsy - obesity - and attention deficit disorder (I wouldn't recommend this)
No. Atropine is used to reduce urgency in mild cystitis. So it would aggravate the urinary retention.
Inhibits cell wall mucopeptide formation - Bactericidal

46. Digoxin v. Digitoxin: half life?
- Tetracycline - amiodarone - sulfonamides
thick ascending limb
Amphotericin B - Nystatin - Fluconazole/azoles
Digitoxin 168hrs Digoxin 40 hrs

47. Which drug(s) cause this reaction: Tubulointerstitial Nephritis (5)?
hypokalemia - slight hyperlipidemia - hyperuricemia - lassitude - hypercalcemia - hyperglycemia
- Penicillin
Amphetamine and Ephedrine
- Sulfonamides - furosemide - methicillin - rifampin - NSAIDS (ex. ASA)

48. What organisms does Griseofulvin target?
Dermatophytes (tinea - ringworm)
1. Bleeding 2. Thrombocytopenia 3. Drug - drug interactions
Nephrotoxicity
Pseudomembranous colitis (C. difficile) - fever - diarrhea

49. What is the category - method of use - and adverse effects of Salmeterol in Asthma treatment?
Beta 2 agonist; used as a long - acting agent for prophylaxis. Adverse effects are tremor and arrhythmia.
- NaHCO3
Corticosteroids; prevent production of leukotrienes from arachodonic acid by blocking phospholipase A2. Drugs of choice in a patient with status asthmaticus (in combination with albuterol.)
Gram + cocci - Haemophilus influenza - Enterobacter aerogenes - Neisseria species - P. mirabilis - E. coli - K. pneumoniae - Serratia marcescens ( HEN PEcKS )

50. Is resistant to penicillinase?
As PABA antimetabolites that inhibit Dihydropteroate Synthase - Bacteriostatic
decrease
Imipenem
- Act on same receptor - Full has greater efficacy