OMSB Pharmacist Exam cheat sheet

First-order elimination: t½ = 0.693/k; steady state reached in ~4-5 half-lives, independent of dose size.

Zero-order elimination (phenytoin, ethanol, high-dose salicylates): constant amount removed per unit time; t½ rises with concentration and dose.

Volume of distribution Vd = Dose/C0; loading dose = Vd × target concentration / bioavailability.

Clearance CL = k × Vd = rate of elimination / plasma concentration; maintenance dose rate = CL × target concentration / F.

Henderson-Hasselbalch: for weak acids pH = pKa + log([A⁻]/[HA]); ionized fraction is poorly lipid-permeable, so acid drugs are trapped in alkaline urine.

Michaelis-Menten (capacity-limited) kinetics: V = Vmax·C/(Km + C); at C << Km behavior is first-order, at C >> Km it is zero-order.

Bioavailability F = (AUC_oral/AUC_IV) × (Dose_IV/Dose_oral); F is reduced by first-pass metabolism, not by distribution.

Enantiomers differ in pharmacodynamics: S-warfarin is ~3-5 times more potent than R-warfarin; S-methacholine is active, R-isomer largely inactive.

Prodrugs require metabolic activation (e.g., enalapril→enalaprilat, codeine→morphine, clopidogrel→active thiol metabolite).

Warfarin: target INR 2-3 for most indications (AF, VTE); 2.5-3.5 for mechanical mitral valve; bridge with heparin when INR is subtherapeutic in high-risk patients.

Digoxin toxicity: nausea, visual changes (yellow-green halos), bradyarrhythmias; risk rises with hypokalemia, hypomagnesemia, hypercalcemia, and renal impairment.

ACE inhibitors cause hyperkalemia, rise in creatinine, dry cough (bradykinin), and angioedema; contraindicated in pregnancy and bilateral renal artery stenosis.

Metformin: first-line for type 2 diabetes; hold before iodinated contrast if eGFR <30 and in acute illness; risk of lactic acidosis; monitor B12.

Asthma step-up: SABA as needed → low-dose ICS → low-dose ICS+LABA or medium-dose ICS → medium/high ICS+LABA; LABA never used as monotherapy in asthma.

Heart failure with reduced EF: ARNI/ACEi/ARB + evidence-based beta-blocker + MRA + SGLT2 inhibitor form the four pillars; diuretics for congestion.

Aminoglycosides: concentration-dependent killing, post-antibiotic effect; monitor trough (or AUC) and renal function; risk of ototoxicity and nephrotoxicity.

Vancomycin: target AUC24/MIC 400-600 for serious MRSA infection; infusion reactions (red man syndrome) are rate-related, not allergic.

Opioid conversion: use equianalgesic tables and reduce calculated dose by 25-50% for incomplete cross-tolerance when rotating.

Medication reconciliation should occur at admission, transfer, and discharge; discrepancies are resolved before orders are activated.

Pharmacovigilance: serious ADR reports go to the national authority; Naranjo scale estimates causality as definite/probable/possible/doubtful.

High-alert medications (insulin, heparin, concentrated electrolytes, chemotherapy, opioids) require independent double-checks and standardized concentrations.

Look-alike/sound-alike names and error-prone abbreviations (U for units, QD, trailing zeros) are targeted by ISMP-style safety practices.

Antimicrobial stewardship: right drug, dose, duration, and de-escalation based on culture; prospective audit and feedback is a core strategy.

Therapeutic drug monitoring is indicated for drugs with narrow therapeutic index and good concentration-effect correlation (vancomycin, aminoglycosides, digoxin, lithium, phenytoin, cyclosporine).

Pharmacogenomics: HLA-B5701 before abacavir; HLA-B1502 before carbamazepine in at-risk Asian populations; TPMT/NUDT15 before thiopurines.

Clinical pharmacokinetics dosing adjusts for renal function using Cockcroft-Gault creatinine clearance for most drug dosing decisions.

Prescription validity requires prescriber identity, patient identity, drug, dose, dosage form, quantity, directions, date, and signature; missing elements require clarification.

A complete label includes patient name, drug name and strength, directions, quantity, date dispensed, expiry where relevant, and pharmacy identifier.

Counselling should cover indication, dose and timing, administration technique, common and serious adverse effects, interactions, and storage.

Inhaler counselling: shake, exhale, seal lips, actuate at start of inspiration, hold breath ~10 seconds, rinse mouth after ICS; use spacer if poor technique.

Warfarin counselling: consistent vitamin K intake, avoid NSAIDs and interacting drugs, report bleeding, carry an anticoagulant card, maintain INR monitoring.

Insulin: rotate injection sites within a region to avoid lipohypertrophy; unopened vials refrigerated, in-use pens at room temperature for the labeled period.

Oral bisphosphonates: take on empty stomach with a full glass of water, stay upright 30 minutes, no food or other drugs for 30-60 minutes.

Narrow therapeutic index drugs (levothyroxine, phenytoin, digoxin, lithium, warfarin) require brand consistency and explicit substitution counselling.

Controlled drug schedules classify by abuse potential and medical use; higher schedules carry stricter record-keeping, storage, and prescription limits.

Prescription requirements for controlled substances typically include prescriber registration number, quantity in words and figures, and limited validity period.

Dispensing errors and near misses should be documented and disclosed; patient disclosure of harmful errors is an ethical and often legal duty.

Patient confidentiality may be breached only where legally required or permitted (e.g., serious public health risk, court order, mandatory reporting).

Pharmacists have a duty to refuse to dispense when the prescription is clearly unsafe or forged, and to document and report the concern.

Record retention for prescriptions, controlled drug registers, and ADR reports follows jurisdiction-specific minimum periods.

Informed consent requires capacity, adequate information, and voluntariness; a competent adult may refuse treatment.

Conflict of interest: gifts or incentives from industry must not influence prescribing or purchasing decisions; declare and avoid where possible.

Scope of practice: pharmacists may not prescribe or substitute outside authorized frameworks; substitution requires legal authority or prescriber approval.