PMDC NRE cheat sheet

Pharmacokinetic core: half-life t½ = 0.693 × Vd / CL; steady state is reached after ~4–5 half-lives, and loading dose = (Vd × target concentration) / bioavailability.

Osmolarity (mOsm/L) ≈ 2×Na + glucose/18 + BUN/2.8; calculated serum osmolality below 275 mOsm/kg suggests hypotonic hyponatremia needing urine osmolality to classify.

Anion gap = Na − (Cl + HCO3), normal 8–12 mEq/L; add 2.5 mEq/L to the gap for every 1 g/dL fall in albumin below 4 g/dL.

Acid-base stepwise: check pH (acidemia <7.35, alkalemia >7.45), then PaCO2 for respiratory direction, then HCO3 for metabolic compensation; Winter formula expected PaCO2 = 1.5×HCO3 + 8 ± 2.

Sensitivity rules out disease when negative (SnNout); specificity rules in disease when positive (SpPin); positive likelihood ratio = sensitivity / (1 − specificity).

Number needed to treat = 1 / absolute risk reduction; attributable risk = incidence in exposed − incidence in unexposed.

Volume of distribution = amount of drug in body / plasma concentration; high Vd (>1 L/kg) implies extensive tissue binding and poor dialyzability.

Biotransformation phases: phase I reactions (CYP450 oxidation, reduction, hydrolysis) create reactive groups; phase II conjugation (glucuronidation, acetylation, sulfation) increases water solubility for renal excretion.

Starling forces: net filtration = (Pc − Pi) − σ(πc − πi); pulmonary edema arises when capillary hydrostatic pressure rises or oncotic pressure falls.

Myocardial oxygen demand rises with heart rate, contractility, and wall tension (Laplace law: tension ∝ pressure × radius / 2 × wall thickness).

Nephron segment transport: proximal tubule reabsorbs ~65% of filtered Na and water; thick ascending limb is impermeable to water and is the site of loop-diuretic action on NKCC2.

Glomerular filtration rate ≈ Kf × (glomerular capillary pressure − Bowman space pressure − oncotic pressure); autoregulation holds GFR stable between MAP ~80–180 mmHg.

Hepatic first-pass metabolism reduces oral bioavailability of drugs with high extraction ratios (e.g., nitrates, propranolol, morphine).

COPD physiology: increased residual volume and decreased FEV1/FVC ratio; emphysema destroys alveolar septa, reducing surface area and elastic recoil.

Anemia classification by MCV: microcytic (<80 fL) points to iron deficiency, thalassemia, or chronic disease; macrocytic (>100 fL) points to B12/folate deficiency or alcohol.

Cardiac output = heart rate × stroke volume; stroke volume depends on preload, afterload, and contractility, and Fick principle gives CO = VO2 / (CaO2 − CvO2).

Therapeutic index = TD50 / ED50; a narrow index (e.g., warfarin, digoxin, lithium) mandates drug-level monitoring.

CYP450 interactions: inhibitors include macrolides, azoles, and grapefruit; inducers include rifampin, carbamazepine, phenytoin, and St. John's wort.

Antidote pairings: acetaminophen–N-acetylcysteine, warfarin–vitamin K, heparin–protamine, opioid–naloxone, benzodiazepine–flumazenil.

Screening test criteria: disease must be common and serious, detectable early, with an accepted treatment and a test that is sensitive, specific, and acceptable to patients.

Informed consent requires capacity, disclosure of risks/benefits/alternatives, comprehension, and voluntariness; emergency exceptions apply when harm is imminent.

Surrogate decision-making follows substituted judgment (patient's prior wishes) before best-interests standard.

Reporting obligations override confidentiality for gunshot wounds, child or elder abuse, and reportable communicable diseases.

Adverse drug reaction types: type A (dose-dependent, predictable, e.g., bleeding on anticoagulant) versus type B (idiosyncratic, unpredictable, e.g., anaphylaxis).