Updated: 2/27/2019


Review Topic
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  • A 24-year-old woman presents to the emergency room for abdominal pain and foul-smelling discharge from her vagina. About 4 days ago, she gave birth to twins via C-section and was sent home without complications. Yesterday, she developed a fever as well as abdominal pain. On physical exam, there is significant tenderness to palpation. She is started on intravenous antibiotic therapy with 2 agents, covering both anaerobes and aerobic gram-negative organisms. (Postpartum endometritis)
  • Drugs
    • amikacin
    • gentamicin
    • neomycin
    • streptomycin
    • tobramycin
  • Mechanism of action
    • irreversibly binds to 30S subunit of bacterial ribosomes
      • prevents initiation complex from forming
      • causes misreading of genetic code
    • requires oxygen for uptake and is effective only against aerobes
    • works synergistically with beta-lactams
    • bactericidal
  • Mechanism of resistance
    • bacterial enzymes inactivate the drug by modifying it through adenylation, acetylation, or phosphorylation
  • Clinical use
    • severe aerobic gram-negative rod infections
      • including Pseudomonas aeruginosa, Acinetobacter, Nocardia, and Actinomycetes
      • P aeruginosa resistant to gentamicin and tobramycin are often susceptible to amikacin
    • neomycin for bowel surgery
    • topical neomycin for superficial skin infections
  • Adverse effects
    • irreversible ototoxicity (cochlear and vestibular)
      • increased with loop diuretics
    • nephrotoxicity
      • increased with cephalosporins
    • neuromuscular blockade
    • teratogen

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Questions (4)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2

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(M1.MC.17.4754) A 67-year-old African American male presents to the emergency room complaining of nausea and right flank pain. He reports that these symptoms have worsened over the past two days. His past medical history is notable for congestive heart failure, hypertension, hyperlipidemia, and diabetes mellitus. He currently takes aspirin, losartan, metoprolol, atorvastatin, hydrochlorothiazide, furosemide, and metformin. He is allergic to fluoroquinolones. His temperature is 102.9°F (39.4°C), blood pressure is 100/50 mmHg, pulse is 120/min, and respirations are 28/min. On exam, he demonstrates right costovertebral angle tenderness. Urinalysis reveals 30 WBCs/hpf and positive leukocyte esterase. He is admitted and started on a broad-spectrum combination intravenous antibiotic. He recovers well and is discharged with plans to follow up in 2 weeks. At his follow-up, he reports that he has developed transient visual blurring whenever he turns his head to the right or left. He also reports that he has fallen at home multiple times. What is the mechanism of action of the drug that is most likely responsible for this patient’s current symptoms? Review Topic | Tested Concept

QID: 108930

Inhibition of ribosomal 30S subunit




Inhibition of ribosomal 50S subunit




Inhibition of dihydropteroate synthase




Inhibition of transpeptidase




Inhibition of DNA gyrase



L 4 B

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(M1.MC.13.3) You are treating a neonate with meningitis using ampicillin and a second antibiotic, X, that is known to cause ototoxicity. What is the mechanism of antibiotic X? Review Topic | Tested Concept

QID: 100068

It binds the 50S ribosomal subunit and inhibits peptidyltransferase




It binds the 50S ribosomal subunit and inhibits formation of the initiation complex




It binds the 30s ribosomal subunit and inhibits formation of the initiation complex




It binds the 30s ribosomal subunit and reversibly inhibits translocation




It binds the 50s ribosomal subunit and reversibly inhibits translocation



L 1 E

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