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 |