Medication Errors
Medication errors are preventable events that may cause patient harm at any stage of the medicines pathway. They are a major patient safety concern in the NHS.
Key Facts
Medication errors cause an estimated 237 million errors annually in England, with avoidable ADRs causing 1,708 deaths Prescribing errors occur in 7-10% of medication orders in UK hospitals The most common error types are wrong dose, wrong drug, and omitted medicines High-risk drugs: Insulin, anticoagulants, opioids, methotrexate, potassium — require extra vigilance LASA (Look-Alike Sound-Alike) drugs are a major source of error (e.g., chlorpromazine/chlorpropamide) Electronic prescribing reduces prescribing errors by approximately 50% but introduces new error types The NHS Patient Safety Strategy uses a Just Culture approach to learning from errors All serious medication errors must be reported via the Yellow Card Scheme (MHRA) and local incident reporting systems
Overview
Key Facts
Medication errors can occur at any stage: prescribing, dispensing, administering, or monitoring. They represent the third most common cause of preventable deaths globally.
Epidemiology
The 2018 University of Sheffield/York study commissioned by the Department of Health estimated:
- 237 million medication errors per year in England
- 66 million potentially clinically significant errors
- Avoidable ADRs: ~1,708 deaths and ~181,626 bed-days per year
- Estimated NHS cost: £98.5 million per year in additional bed-days alone
Aetiology
Contributory factors:
- Individual: Fatigue, distraction, knowledge gaps, inexperience
- Team: Poor communication, inadequate handover, hierarchy
- Organisational: Understaffing, workload pressures, inadequate training
- System: Poor IT systems, similar packaging, complex regimens
- Patient factors: Polypharmacy, renal/hepatic impairment, allergies
Pathophysiology
The Swiss Cheese Model (James Reason) explains how errors occur when multiple system defences have aligned failures. Error types:
- Slips: Unintended actions (e.g., picking up wrong drug from shelf)
- Lapses: Omissions (e.g., forgetting to prescribe a drug)
- Mistakes: Incorrect decisions (e.g., wrong dose calculation)
- Violations: Intentional rule-breaking (e.g., not checking allergies)
Clinical Presentation
Types of Medication Error
- Prescribing errors: Wrong drug, dose, route, frequency, duration; drug interactions; allergy not checked
- Dispensing errors: Wrong drug dispensed, wrong label, wrong quantity
- Administration errors: Wrong time, wrong route (e.g., IV instead of oral), wrong patient
- Monitoring errors: Failure to monitor drug levels, renal function, INR
High-Risk Situations
- Transitions of care (admission, discharge, transfer)
- Out-of-hours prescribing
- Verbal orders
- Paediatric/neonatal prescribing (weight-based dosing)
- Renal/hepatic impairment (dose adjustment needed)
Red Flags (Events Requiring Immediate Action)
- Intrathecal vincristine (universally fatal)
- Insulin overdose (severe hypoglycaemia)
- Anticoagulant overdose (haemorrhage)
- 10-fold dosing errors in paediatrics
- Concentrated potassium given as IV bolus (cardiac arrest)
Differential Diagnosis
| Diagnosis | Key Features | Investigation |
|---|---|---|
| Medication error | Identifiable deviation from correct practice | Incident review, medication chart review |
| Adverse drug reaction (predictable) | Expected pharmacological effect (Type A) | Drug level, clinical assessment |
| Adverse drug reaction (unpredictable) | Idiosyncratic, allergic (Type B) | Drug challenge, immunological tests |
| Drug interaction | New drug added, altered effect | Review all medications, drug interaction checker |
| Non-adherence | Patient not taking medicines as prescribed | Medication review, patient interview |
| Prescribing cascade | New drug prescribed to treat side effect of another | Comprehensive medication review |
Diagnosis / Investigation
Bedside
- Medication chart review: Check all prescriptions for accuracy
- Patient interview: Establish what was taken and when
- Observations: Monitor for clinical effects of error
Bloods
- Drug levels: Where available (digoxin, lithium, phenytoin, aminoglycosides)
- U&Es, LFTs: Assess for drug-related organ damage
- Clotting: If anticoagulant error
- Blood glucose: If insulin error
Imaging
- As clinically indicated based on the specific error and clinical consequences
Special Tests
- Root cause analysis: For serious incidents
- Incident reporting: Datix or equivalent system
- Yellow Card reporting: To MHRA for serious ADRs
Management
Non-pharmacological
- Immediate: Assess patient, identify error, implement corrective action
- Documentation: Record error in clinical notes, complete incident report
- Duty of Candour: Open and honest communication with patient/family (legal requirement)
- Root cause analysis: For serious incidents — identify system failures
- Learning: Share lessons through governance meetings, safety bulletins
Pharmacological
- Specific antidotes: Naloxone (opioid overdose), flumazenil (benzodiazepine), N-acetylcysteine (paracetamol), vitamin K/PCC (warfarin), protamine (heparin), glucagon/dextrose (insulin)
- Supportive care: As required based on clinical effects
Prevention Strategies
- Electronic prescribing with clinical decision support
- Medicines reconciliation at all transitions of care
- Independent double-checking of high-risk drugs
- Standardised prescribing protocols
- Clinical pharmacist ward presence
- LASA drug awareness
- Tall man lettering (e.g., DOBUTamine vs DOPamine)
Referral Criteria
- Serious harm: Report to MHRA, refer to coroner if death
- Systemic issues: Escalate to patient safety team
- Repeated errors: Review training needs, consider professional support
Prognosis
- Most medication errors cause no harm (estimated 72% are intercepted or clinically insignificant)
- Serious harm occurs in approximately 1-2% of medication errors
- UK hospital mortality attributable to medication errors: estimated 1,700+ deaths annually
- Implementation of electronic prescribing reduces error rates by 30-50%
- Clinical pharmacist-led medicines reconciliation reduces errors at discharge by 70%
Other Relevant Information
High-Alert Medications
| Drug Category | Specific Risks | Safety Measures |
|---|---|---|
| Insulin | Hypoglycaemia, 10x dose errors | Dedicated insulin chart, independent double-check |
| Anticoagulants | Haemorrhage | INR monitoring, dosing protocols |
| Opioids | Respiratory depression | Ceiling dose awareness, naloxone availability |
| Methotrexate (oral) | Pancytopenia if taken daily instead of weekly | Clear weekly dosing, patient education |
| Potassium (IV) | Fatal if given as bolus | Pre-mixed solutions only, never on ward stock |
Medication Error Classification (NCC MERP)
| Category | Description |
|---|---|
| A | Circumstances with capacity to cause error |
| B | Error occurred but did not reach patient |
| C | Error reached patient but no harm |
| D | Error reached patient, monitoring needed |
| E-F | Error caused temporary harm |
| G-H | Error caused permanent harm |
| I | Error contributed to death |