Prescribing Practices
Introduction
Prescribing practices form a cornerstone of the Medical Council of Canada Qualifying Examination Part I (MCCQE1), particularly under the Population Health, Ethical, Legal, and Organizational Aspects of Medicine (PHELO) category. In the Canadian context, prescribing is not merely about selecting the right drug; it involves a complex interplay of clinical judgment, legal obligations, patient safety, and resource stewardship.
For an MCCQE1 candidate, mastery of this topic requires understanding the CanMEDS roles, specifically Medical Expert (clinical knowledge), Communicator (shared decision-making), and Professional (regulatory adherence).
MCCQE1 Tip: The exam frequently tests your ability to identify medication errors, apply the principles of deprescribing in the elderly, and navigate the legal requirements for controlled substances in Canada.
Legal and Regulatory Framework in Canada
Prescribing in Canada is a shared responsibility between federal and provincial jurisdictions.
Federal Legislation
The Controlled Drugs and Substances Act (CDSA) is the federal law that governs the possession, production, and distribution of controlled substances (e.g., opioids, benzodiazepines, stimulants).
- Health Canada oversees the approval and safety monitoring of drugs.
- Narcotic Control Regulations: Dictate how narcotics must be prescribed and dispensed.
Provincial Regulation
While the federal government approves drugs, the practice of prescribing is regulated provincially by the Colleges of Physicians and Surgeons (e.g., CPSO in Ontario, CPSBC in British Columbia).
- Prescription Monitoring Programs (PMP): Most provinces have specific programs (formerly Triplicate Prescription Programs) to monitor high-risk drugs like opioids to prevent diversion and abuse.
The “Valid” Prescription
In Canada, a prescription is only valid if a patient-physician relationship exists. “Internet prescribing” without a direct assessment is generally considered professional misconduct unless specific telemedicine standards are met.
Principles of Safe Prescribing
To minimize errors, Canadian physicians are encouraged to adhere to the WHO Guide to Good Prescribing and the “Rights” of medication administration.
The 7 Rights of Medication Safety
- Right Patient (Two identifiers)
- Right Drug
- Right Dose
- Right Route
- Right Time/Frequency
- Right Reason/Indication
- Right Documentation
The Prescribing Process
Step 1: Define the Patient’s Problem
Determine the diagnosis and the therapeutic objective (e.g., cure infection, relieve pain, prevent stroke).
Step 2: Specify the Therapeutic Objective
What do you want to achieve? (e.g., Lower BP to <130/80 mmHg).
Step 3: Verify Suitability (The “P-drug” concept)
Check for contraindications, interactions, and allergies. Consider renal and hepatic function, especially in the elderly (Creatinine Clearance).
Step 4: Write the Prescription
Ensure legibility and completeness. Use generic names to avoid confusion.
Step 5: Inform the Patient
Discuss side effects, warnings, and instructions (Communicator role).
Step 6: Monitor Treatment
Determine when to follow up and what parameters to check (e.g., INR for warfarin, TSH for levothyroxine).
Medication Safety and Error Prevention
Medication errors are a leading cause of preventable harm. The Institute for Safe Medication Practices Canada (ISMP Canada) publishes guidelines to prevent these errors.
Dangerous Abbreviations
The MCCQE1 expects you to know which abbreviations are banned because they lead to errors.
| Do Not Use | Potential Problem | Use Instead |
|---|---|---|
| U, u (unit) | Mistaken for “0” (zero), “4” (four), or “cc” | Write “unit” |
| IU (International Unit) | Mistaken for “IV” (intravenous) or “10” (ten) | Write “International Unit” |
| Q.D., QD, q.d., qd | Mistaken for “Q.O.D.” or “qid” | Write “daily” |
| Q.O.D., QOD | Mistaken for “Q.D.” | Write “every other day” |
| Trailing zero (X.0 mg) | Decimal point is missed (read as X0 mg) | Write “X mg” |
| Lack of leading zero (.X mg) | Decimal point is missed (read as X mg) | Write “0.X mg” |
| MS, MSO4, MgSO4 | Confused for one another | Write “morphine sulfate” or “magnesium sulfate” |
Medication Reconciliation (MedRec)
MedRec is a formal process required by Accreditation Canada at care transitions (admission, transfer, discharge).
- Goal: To prevent discrepancies between pre-admission meds and hospital orders.
- BPMH: Best Possible Medication History is the gold standard foundation for MedRec.
Adverse Drug Reactions (ADRs) and Vanessa’s Law
Vanessa’s Law (Protecting Canadians from Unsafe Drugs Act) requires hospitals to report serious adverse drug reactions and medical device incidents to Health Canada.
- It is not just an ethical duty but a legal requirement for healthcare institutions.
Special Populations and Considerations
Geriatrics
Polypharmacy & Deprescribing
- Polypharmacy: Generally defined as using 5 or more medications.
- Prescribing Cascade: Treating the side effect of one drug with another drug (e.g., Amlodipine causes edema -> Furosemide prescribed).
- Tools:
- Beers Criteria: List of potentially inappropriate medications in older adults (e.g., Benzodiazepines, Anticholinergics).
- STOPP/START Criteria: Screening Tool of Older Persons’ Prescriptions.
- Renal Dosing: Always calculate eGFR or CrCl before prescribing.
Canadian Guidelines
Opioid Prescribing (2017 Canadian Guideline)
For chronic non-cancer pain:
- Optimization: Optimize non-opioid pharmacotherapy and non-pharmacological therapy first.
- Threshold: Avoid increasing doses to 90 mg morphine equivalents (MME) per day.
- Rotation: If benefits do not outweigh risks, consider tapering or rotating.
Antimicrobial Stewardship (Choosing Wisely Canada)
- Viral Infections: Do not prescribe antibiotics for upper respiratory viral infections (e.g., bronchitis, sinusitis <7 days).
- Asymptomatic Bacteriuria: Do not treat in non-pregnant adults or those not undergoing urologic procedures.
Diabetes Canada (2018/2020 Guidelines)
- Metformin: First-line therapy for Type 2 Diabetes.
- Cardioprotection: Use SGLT2 inhibitors or GLP-1 receptor agonists for patients with established atherosclerotic cardiovascular disease.
Key Points to Remember for MCCQE1
- Prescription Writing: Always write out “daily” or “every other day.” Never use trailing zeros (e.g., write 5 mg, NOT 5.0 mg).
- Benzodiazepines in Elderly: High yield. Avoid them. They increase the risk of falls, delirium, and fractures.
- Interactions: Watch for CYP450 interactions.
- Inducers: Carbamazepine, Rifampin, Phenytoin, St. John’s Wort (mnemonic: CRAPS).
- Inhibitors: Cimetidine, Ciprofloxacin, Azoles, Macrolides (except Azithromycin), Grapefruit juice.
- Codeine: Contraindicated in children <12 years old and breastfeeding mothers (risk of respiratory depression in ultra-rapid metabolizers).
- Consent: Prescribing a new medication requires informed consent (Nature, Risks, Benefits, Alternatives).
Sample Question
Scenario
A 78-year-old woman presents to her family physician for a routine follow-up. She has a history of hypertension, insomnia, and osteoarthritis. Her daughter mentions that the patient has had two falls in the last month but sustained no injuries. Her current medications include Amlodipine 5 mg daily, Acetaminophen 500 mg qid prn, and Lorazepam 1 mg at bedtime for sleep. Her blood pressure is 135/80 mmHg. Physical examination is unremarkable aside from mild crepitus in the knees.
Which of the following is the most appropriate next step in the management of this patient’s medication regimen?
Options
- A. Increase Amlodipine to 10 mg daily
- B. Add Alendronate 70 mg weekly
- C. Initiate a taper of Lorazepam
- D. Switch Acetaminophen to Ibuprofen 400 mg tid
- E. Add Melatonin 3 mg at bedtime
Explanation
The correct answer is:
- C. Initiate a taper of Lorazepam
Detailed Explanation: This patient is experiencing falls, which is a major geriatric syndrome. The most significant modifiable risk factor in her medication list is the use of Lorazepam (a benzodiazepine).
- Choice C is correct: Benzodiazepines are included in the Beers Criteria as medications to avoid in older adults due to increased sensitivity and decreased metabolism. They are strongly associated with cognitive impairment, delirium, falls, and fractures. Deprescribing (tapering) is the most appropriate action to reduce fall risk.
- Choice A is incorrect: Her BP is 135/80 mmHg, which is acceptable for an elderly patient (target generally <140/90 mmHg or <130/80 mmHg depending on comorbidities, but not the priority over fall risk).
- Choice B is incorrect: While she is at risk for fractures due to falls, bisphosphonates (Alendronate) are indicated for osteoporosis. There is no evidence of osteoporosis provided (no DEXA scan result), and preventing the fall (removing the cause) is the primary prevention strategy.
- Choice D is incorrect: NSAIDs (Ibuprofen) should be avoided in the elderly if possible due to GI bleeding, renal, and cardiovascular risks (Beers Criteria).
- Choice E is incorrect: Adding Melatonin constitutes polypharmacy. While safer than benzodiazepines, the priority is to remove the offending agent (Lorazepam) first.
References
- Medical Council of Canada. (n.d.). MCCQE Part I Clinical Decision-Making and Multiple-Choice Question Guidelines.
- Institute for Safe Medication Practices Canada (ISMP Canada). (n.d.). Do Not Use: Dangerous Abbreviations, Symbols and Dose Designations. Retrieved from ISMP Canada
- Busse, J. W., et al. (2017). Guideline for opioid therapy and chronic noncancer pain. CMAJ, 189(18), E659-E666.
- American Geriatrics Society. (2019). 2019 American Geriatrics Society Beers Criteria® Update Expert Panel. American Geriatrics Society 2019 Updated AGS Beers Criteria® for Potentially Inappropriate Medication Use in Older Adults. J Am Geriatr Soc.
- Choosing Wisely Canada. (n.d.). Antibiotics: When you need them and when you don’t. Retrieved from Choosing Wisely Canada
- Government of Canada. (2014). Vanessa’s Law (Protecting Canadians from Unsafe Drugs Act).