10.2 Pharmacoeconomics and Pharmacoepidemiology

10.2 Pharmacoeconomics and Pharmacoepidemiology

Exam Focus: The PEBC Evaluating Examination evaluates competency in health economics, reimbursement decision frameworks, and pharmacoepidemiology. Pharmacists must differentiate the four primary pharmacoeconomic study designs (CMA, CEA, CUA, CBA), calculate Incremental Cost-Effectiveness Ratios ($ICER$), understand Quality-Adjusted Life Years ($QALY$), and understand the roles of Canada's Drug Agency (CDA-AMC / CADTH), INESSS, pCPA, PMPRB, and post-marketing surveillance via MedEffect Canada.

---

Foundations of Pharmacoeconomic Evaluation

Pharmacoeconomics identifies, measures, and compares the costs and consequences of pharmaceutical products, clinical pharmacy services, and healthcare strategies. Because healthcare resources are finite, pharmacoeconomic analyses guide formulary listings, clinical practice guidelines, and public policy decisions.

Perspectives of Economic Evaluation

The perspective determines which costs and benefits are included in the analysis:

1. Patient Perspective: Captures out-of-pocket prescription expenses, co-pays, travel costs, and lost personal wages.
2. Payer / Insurer Perspective (Provincial Drug Plan): Captures covered drug acquisition costs, professional dispensing fees, and reimbursed clinical services.
3. Healthcare System Perspective: Captures all costs incurred by the public healthcare sector, including drug costs, physician billing, laboratory testing, emergency room visits, and inpatient hospitalizations (preferred by Canadian health technology agencies).
4. Societal Perspective: The broadest perspective; includes all direct medical costs, direct non-medical costs, and indirect productivity losses across society (absenteeism, disability, premature death).

---

Cost Categorization and Discounting

+-------------------------------------------------------------------------+
|                        HEALTHCARE COST CATEGORIES                       |
+-------------------------------------------------------------------------+
|  1. DIRECT MEDICAL COSTS:                                               |
|     - Drug acquisition and compounding costs                            |
|     - Pharmacist professional dispensing fees & clinical cognitive fees |
|     - Hospital bed stays, nursing care, surgical suites, physician fees |
|     - Diagnostic imaging, therapeutic drug monitoring, laboratory tests |
|                                                                         |
|  2. DIRECT NON-MEDICAL COSTS:                                           |
|     - Patient transportation (ambulance, taxis, transit to dialysis)    |
|     - Specialized lodging and meals during out-of-town oncology care    |
|     - Childcare services required during medical appointments           |
|                                                                         |
|  3. INDIRECT COSTS (PRODUCTIVITY LOSSES):                               |
|     - Absenteeism (missed workdays due to illness)                      |
|     - Presenteeism (reduced workplace productivity while ill)           |
|     - Premature disability or death (loss of economic lifetime output)  |
|                                                                         |
|  4. INTANGIBLE COSTS:                                                   |
|     - Physical pain, anxiety, emotional suffering, fatigue, grief       |
|     - Difficult to quantify in dollars; captured via utility instruments|
+-------------------------------------------------------------------------+

Discounting

Costs and clinical consequences that occur in the future are valued less than those occurring in the present (time preference). When an economic model extends beyond a 1-year time horizon, future costs and outcomes must be adjusted to present value using discounting: $\text{Present Value (PV)} = \frac{\text{Future Value (FV)}}{(1 + r)^t}$ In Canadian health economic evaluations, the Canadian Agency for Drugs and Technologies in Health (CADTH / CDA-AMC) guidelines recommend an annual base-case discount rate of 1.5% (historically 5.0%), tested across a range of 0% to 3.0% in sensitivity analyses.

---

The Four Core Pharmacoeconomic Methodologies

---

Cost-Utility Analysis, QALYs, and the ICER

Calculating Quality-Adjusted Life Years (QALYs)

A QALY combines both the length of life (quantity) and health-related quality of life (quality) into a single composite metric: $\text{QALY} = \text{Additional Years of Life Gained} \times \text{Utility Weight ($U$)}$

• Utility ($U$): A standardized preference score on a continuous scale from 0.0 (death) to 1.0 (perfect health).
• Example: A patient living for 5 years with severe rheumatoid arthritis at a utility weight of $0.60$ gains $5 \times 0.60 = 3.0\text{ QALYs}$.

Methods of Utility Elicitation

• Standard Gamble (SG): The classic choice model under risk; the patient chooses between remaining in their current chronic health state versus taking a gamble with probability $p$ of perfect health and $1 - p$ of immediate death.
• Time Trade-Off (TTO): The patient decides how many years of life in their current suboptimal health state they would trade to live a shorter duration in perfect health.
• Multi-Attribute Utility Instruments: Validated questionnaires including the EQ-5D (EuroQol 5-Dimension: mobility, self-care, usual activities, pain/discomfort, anxiety/depression), SF-6D, and Health Utilities Index (HUI).

The Incremental Cost-Effectiveness Ratio (ICER)

The ICER calculates the additional economic cost incurred per additional unit of clinical outcome achieved when comparing a new intervention ($A$) against an active comparator or standard of care ($B$): $\text{ICER} = \frac{\text{Cost}_A - \text{Cost}_B}{\text{Effect}_A - \text{Effect}_B} = \frac{\Delta\text{Cost}}{\Delta\text{Effect}}$

+-------------------------------------------------------------------------+
|                    THE COST-EFFECTIVENESS PLANE                         |
+-------------------------------------------------------------------------+
|                   Incremental Cost (+Delta C)                           |
|                               |                                         |
|        QUADRANT IV            |           QUADRANT I                    |
|   DOMINATED (Reject)          |   Trade-off: More effective, more costly|
|   Higher cost, lower effect   |   Accept if ICER < WTP threshold        |
|                               |   (e.g., < $50,000 / QALY)              |
|  -----------------------------+-----------------------------            |
|  -Delta Effect                |               +Delta Effect             |
|  (Less Effective)             |               (More Effective)          |
|                               |                                         |
|        QUADRANT III           |           QUADRANT II                   |
|   Trade-off: Less costly,     |   DOMINANT (Accept)                     |
|   less effective              |   Lower cost, higher effect             |
|                               |                                         |
|                   Incremental Cost (-Delta C)                           |
+-------------------------------------------------------------------------+

• Dominant (Quadrant II): The new therapy is cheaper and more effective (adopt immediately).
• Dominated (Quadrant IV): The new therapy is more expensive and less effective (reject completely).
• Willingness-to-Pay (WTP) Threshold: In Canada, therapies with an ICER below $50,000 to $100,000 per QALY gained are generally considered cost-effective by public reimbursement frameworks.

Economic Modeling and Sensitivity Analysis

• Decision Trees: Used for short-term, discrete clinical events (e.g., acute surgical prophylaxis).
• Markov State-Transition Models: Used for chronic, recurring disease states where patients transition between defined health states (e.g., Well $\rightarrow$ Relapse $\rightarrow$ Major Complication $\rightarrow$ Death) over repetitive cycles across their lifetime.
• Sensitivity Analysis: Tests model robustness against parameter uncertainty:
  • Deterministic (One-way / Multi-way): Varies one variable at a time across its plausible range; visualized using Tornado Diagrams.
  • Probabilistic Sensitivity Analysis (PSA): Uses Monte Carlo simulations where all model parameters vary simultaneously according to probability distributions; visualized via Cost-Effectiveness Acceptability Curves (CEAC).

---

The Canadian Health Technology Assessment and Drug Pricing Landscape

In Canada, pharmaceutical market access and reimbursement follow a rigorous, multi-tiered regulatory and economic process.

+-------------------------------------------------------------------------+
|               CANADIAN PHARMACEUTICAL REIMBURSEMENT PIPELINE            |
+-------------------------------------------------------------------------+
|  1. HEALTH CANADA:                                                      |
|     Evaluates Safety, Efficacy, and Quality --> Issues NOC              |
|                                |                                        |
|                                v                                        |
|  2. HEALTH TECHNOLOGY ASSESSMENT (HTA):                                 |
|     - Canada's Drug Agency (CDA-AMC / CADTH: CDR & pCODR)               |
|     - INESSS (Quebec)                                                   |
|     Evaluates Clinical Efficacy, Cost-Effectiveness & Ethics -->        |
|     Issues Reimbursement Recommendations (Reimburse / Do Not Reimburse) |
|                                |                                        |
|                                v                                        |
|  3. PRICE NEGOTIATION: pan-Canadian Pharmaceutical Alliance (pCPA)      |
|     Conducts collective pricing negotiations with drug manufacturers -->|
|     Establishes Letter of Intent (LOI) and confidential rebates         |
|                                |                                        |
|                                v                                        |
|  4. PROVINCIAL/TERRITORIAL FORMULARY LISTING:                           |
|     Individual jurisdictions (ODB, Fair PharmaCare, etc.) add drug to   |
|     provincial public formularies based on local budgets & criteria     |
|                                                                         |
|  * PMPRB (Federal Regulator): Sets maximum factory-gate ceiling prices  |
|    to prevent excessive patented drug pricing throughout.               |
+-------------------------------------------------------------------------+

Key Canadian Organizations

1. Health Canada: Grants market authorization (Notice of Compliance [NOC]) based strictly on clinical safety, efficacy, and manufacturing quality.
2. Canada's Drug Agency (CDA-AMC, formerly CADTH):
   • Operates the Common Drug Review (CDR) (non-oncology pharmaceuticals) and the pan-Canadian Oncology Drug Review (pCODR).
   • Issues independent, evidence-based reimbursement recommendations to federal, provincial, and territorial drug plans: (1) Reimburse, (2) Reimburse with clinical criteria and/or cost conditions, or (3) Do not reimburse.
3. INESSS (Institut national d'excellence en santé et en services sociaux): Performs equivalent HTA assessments specifically for the province of Quebec.
4. pan-Canadian Pharmaceutical Alliance (pCPA): An alliance of provincial, territorial, and federal public drug plans that conducts joint price negotiations with manufacturers for brand-name and generic drugs to secure maximum value and confidential rebates.
5. Patented Medicine Prices Review Board (PMPRB): An independent, quasi-judicial federal watchdog established under the Patent Act that limits the maximum factory-gate prices charged by manufacturers for patented medicines to ensure they are not excessive.

---

Pharmacoepidemiology and Post-Marketing Surveillance

Pharmacoepidemiology is the study of the utilization and effects of drugs in large populations. It bridges clinical pharmacology with epidemiology to evaluate real-world safety and effectiveness.

Post-Marketing Surveillance (Phase IV Studies)

Clinical trials (Phases I-III) suffer from inherent limitations: small sample sizes ($n < 3,000$), short follow-up durations, rigid inclusion criteria, and exclusion of vulnerable populations (pediatrics, geriatrics, pregnancy). Phase IV post-marketing surveillance identifies:

• Rare adverse drug reactions (ADRs occurring in $< 1$ in $10,000$ patients).
• Long-term chronic toxicities and delayed oncogenic effects.
• Drug-drug and drug-disease interactions in complex multimorbid patients.
• Real-world off-label utilization patterns.

Pharmacoepidemiological Study Designs

• Prospective and Retrospective Cohort Studies: Track exposed and unexposed populations forward or backward in time to calculate Relative Risk ($RR$) and incidence rates.
• Nested Case-Control Studies: Cases with an adverse event are matched with controls from within an established defined cohort.
• Self-Controlled Case Series (SCCS): Individuals act as their own controls, comparing adverse event rates during risk exposure windows versus unexposed baseline periods (eliminates between-person confounding).

Health Canada MedEffect Canada / Canada Vigilance Program

• Canada Vigilance Program: The national post-marketing surveillance program operated by Health Canada that collects and assesses spontaneous adverse reaction reports from healthcare professionals (pharmacists, physicians) and consumers.
• Vanessa's Law (Protecting Canadians from Unsafe Drugs Act): Mandates that Canadian hospitals report all Serious Adverse Drug Reactions (SADRs) and Medical Device Incidents (MDIs) to Health Canada within 30 calendar days of documentation.
• Signal Detection: Disproportionality algorithms including the Proportional Reporting Ratio (PRR) and Reporting Odds Ratio (ROR) identify emerging pharmacovigilance safety signals.