UWorld incorrect

Question 1

Methotrexate mechanism

Answer 1

Irreversible folate antagonist of DHF reductase

DHF –> THF blocked. So, DHF polyglutamate builds up

Question 2

Isoniazid mechanism of resistance

Answer 2

Mycobacterial cat peroxidase or binding site on mycolic acid synthesis enzyme

Question 3

Lipid soluble drugs

Answer 3

1. High potency (low MAC - amount to prevent 50% patients from responding to pain)
2. Enter brain

Question 4

Blood soluble drugs

Answer 4

Large AV gradient = Slow onset to blood saturation and slow onset

Question 5

PTU mechanism and prednisone use in Graves’

Answer 5

Blocks Thyroid peroxidase (Methimazole ) + T4–>T3 conversion (beta blockers)

Prednisone for myxedema/opthalmopathy

Question 6

Amphotericin and Nystatin mechanism

Answer 6

Bind ergosterol –> cause hole in cell membrane

Question 7

Caspofungin mechanism

Answer 7

Block synthesis of glucan in cell walls

Question 8

Griseofulvin mechanism

Answer 8

Mitosis microtubule spindle inhibition

Question 9

gynecomastia mechanism and treatment

Answer 9

Non-medication:
Obesity (increased aromatase)
Hyperthyroidism (Increased LH secretion and estrogen production)
Cirrhosis (Decreased clearance and increased aromatase)
CKD (Decreased testosterone production)

Medication related:
Leuprolide, ketoconazole - decreased testosterone production
Spironolactone, flutamide - testosterone receptor antagonist

Treatment: Tamoxifen

Question 10

Nitric oxide vs Nitrous oxide

Answer 10

Nitric oxide - pulmonary HTN/neonate (NO)

Nitrous oxide - laughing gas - low potency, high lipid solubility (N20)