PEBC cheat sheet

Bioavailability equations: absolute F = (AUC_oral × D_IV) / (AUC_IV × D_oral); relative F compares two extravascular products using the same dose ratio correction.

Volume of distribution Vd = Dose / C0 (extrapolated); clearance CL = Dose/AUC = Vd × k; half-life t½ = 0.693 × Vd / CL.

Steady state is reached after ~4–5 half-lives; loading dose = (Vd × target concentration) / F, maintenance dose rate = (CL × target concentration) / F.

Zero-order elimination shows constant amount removed per time (t½ rises as concentration falls, e.g., phenytoin, ethanol, ASA at high dose); first-order shows constant fraction removed.

Renal dosing: Cockcroft-Gault CrCl = [(140 − age) × weight × (0.85 if female)] / (72 × SCr); dose adjustment follows fraction of normal renal function.

CYP inhibitors (mnemonic-based): azoles, macrolides, protease inhibitors, grapefruit, cimetidine; inducers: rifampin, carbamazepine, phenytoin, St. John's wort, smoking.

Therapeutic index narrow drugs requiring monitoring: digoxin, lithium, phenytoin, warfarin, cyclosporine, tacrolimus, vancomycin, aminoglycosides.

Pharmacogenomics: CYP2C19 poor metabolizers reduce clopidogrel activation; CYP2D6 ultrarapid metabolizers reduce codeine/tramadol efficacy and raise toxicity; HLA-B*5701 predicts abacavir hypersensitivity.

Standard station structure: read the scenario, identify the request and the patient's key concerns, gather missing information, then give a prioritized recommendation with monitoring and follow-up.

Red-flag referral triggers: chest pain, sudden severe headache, stroke signs, anaphylaxis, GI bleeding, suicidal ideation, acute vision loss, and suspected sepsis require urgent escalation rather than self-care advice.

Counseling sequence: medication name and purpose, dose and timing, expected onset, common and serious adverse effects, administration technique, missed dose, storage, and when to seek help.

Prescription validity checks: patient identifiers, drug, dose, route, frequency, quantity, date, prescriber signature; clarify ambiguous or incomplete orders before dispensing.

Anticoagulant counseling: consistent vitamin K intake for warfarin, INR target and monitoring, bleeding signs, and drug/food interactions; DOACs require renal function and adherence emphasis.

Opioid safety: assess indication, dose, sedation, constipation prophylaxis, naloxone provision, and combination with benzodiazepines or alcohol; document a treatment agreement where applicable.

Asthma/COPD inhaler teaching: demonstrate and observe technique, use spacer with MDI, rinse mouth after ICS, distinguish reliever from controller, and confirm action plan.

Antimicrobial stewardship communication: confirm indication and duration, explain completing the course, resistance, and adverse effects, and check allergies before recommending therapy.