10.5 Drug Information and Evidence-Based Decision Making

10.5 Drug Information and Evidence-Based Decision Making

Exam Focus: The blueprint's literature evaluation subcategory covers "evidence-based decision making" alongside critical appraisal and biostatistics. Items test which source to use for which question and how a well-formed question is constructed.

---

The Drug Information Request Process

A structured process prevents the two most common failures: answering a different question than the one that was asked, and providing information that cannot be acted on.

1. Secure demographics and background. Who is asking, in what role, and how urgently? A question from a patient, a nurse, and a specialist about the same drug require different depth, framing, and vocabulary.
2. Obtain the background and the true question. "Can you take ibuprofen with warfarin?" is often really "my mother is on warfarin and her knee is agonising — what can she take?" Ask what prompted the question, whether it concerns a specific patient, and what has already been tried.
3. Classify the request — availability, dosing, adverse effects, interactions, therapeutic use, use in pregnancy or lactation, toxicity, compounding, identification. Classification points to the right resource immediately.
4. Search systematically, moving through the source hierarchy and documenting what was searched and what terms were used.
5. Evaluate, analyse, and synthesise. Weigh study quality and applicability rather than reporting whatever the first source said.
6. Formulate and communicate the response. Answer the question directly first, then justify it, then state the limitations. State the strength of the evidence honestly.
7. Document and follow up. Record the question, the sources, the answer, and the recommendation, and confirm the answer was usable.

---

Source Hierarchy

Start tertiary. It is fastest and most reliable for established knowledge. Move to secondary and primary sources when the question is new, controversial, unusually specific, or when the tertiary sources disagree.

Canadian-specific resources matter on this examination because practice, product availability, and regulation differ from the United States: the Compendium of Pharmaceuticals and Specialties (CPS) and its patient-facing companion, e-Therapeutics+, the Health Canada Drug Product Database for authorised products and Drug Identification Numbers, the Canadian Immunization Guide, provincial formularies, and Canadian clinical practice guidelines from bodies such as Diabetes Canada, Hypertension Canada, the Canadian Cardiovascular Society, and the Canadian Thoracic Society.

Evaluate any source for authorship and expertise, date and currency, referencing, funding and conflicts of interest, peer review, and applicability to the Canadian setting. A well-designed website is not evidence, and a manufacturer-sponsored summary is a starting point rather than an answer.

---

Asking an Answerable Question

Background questions ask for general knowledge — what is the usual dose, what are the common adverse effects — and are answered from tertiary sources.

Foreground questions ask for a specific clinical decision and are structured with PICO:

A PICO-structured question specifies which evidence would answer it and which study design would provide it: therapy questions are best answered by randomised controlled trials and their systematic reviews, harm questions frequently by cohort or case-control studies, diagnosis questions by cross-sectional studies against a reference standard, and prognosis questions by cohort studies.

---

Evidence-Based Practice

Evidence-based practice is the integration of three components, none of which is sufficient alone:

1. The best available external evidence.
2. Individual clinical expertise, which determines whether the evidence applies to this patient and recognises what the trial population excluded.
3. The patient's values and preferences, which determine what counts as a good outcome.

The five steps are: ask an answerable question, acquire the evidence, appraise it critically, apply it to the patient, and assess the outcome.

Two practical cautions the examination rewards:

• Applicability. Trials commonly exclude the very old, those with significant kidney or liver disease, and those on multiple medications — precisely the patients pharmacists most often see. Ask whether your patient would have been enrolled.
• Guidelines are not evidence. They are interpretations of evidence, and they carry the judgements and potential conflicts of their authors. Read the strength of recommendation and the quality of underlying evidence, which most Canadian guidelines grade explicitly, rather than the recommendation alone. Where guidelines conflict, compare their publication dates, the evidence each considered, and the population each addressed.

Absence of evidence is not evidence of absence. A trial that fails to demonstrate benefit may have been too small or too short to detect one. Say what is known, what is not known, and what you would recommend given the uncertainty.