Clinical Opiate Withdrawal Scale (COWS) for Assessing Opioid Withdrawal
The Clinical Opiate Withdrawal Scale (COWS) is the standard clinician-administered assessment tool for diagnosing and quantifying opioid withdrawal severity. 1
What is COWS?
The COWS is an 11-item objective assessment performed by a clinician that evaluates specific physical signs and symptoms of opioid withdrawal 1, 2. This tool provides a numerical score that directly correlates with withdrawal severity and guides treatment decisions 3.
The 11 Components Assessed
The COWS evaluates the following withdrawal manifestations with weighted scoring 3, 1:
- Resting pulse rate (0-4 points based on heart rate ranges) 3
- Sweating (autonomic symptom assessment) 1
- Restlessness (observed during assessment) 3
- Pupil size (0-5 points) 1
- Bone or joint aches 1
- Runny nose or tearing (0-4 points) 3
- Gastrointestinal upset (0-5 points for nausea, vomiting, diarrhea) 3
- Tremor (observation of outstretched hands, 0-4 points) 3
- Yawning (0-4 points based on frequency during assessment) 3
- Anxiety or irritability (0-4 points) 3
- Gooseflesh/piloerection (0-5 points) 3
Scoring Interpretation
The total COWS score determines withdrawal severity 3:
- 5-12 points: Mild withdrawal 3
- 13-24 points: Moderate withdrawal 3
- 25-36 points: Moderately severe withdrawal 3
- >36 points: Severe withdrawal 3
Clinical Applications
COWS is primarily used to determine the appropriate timing and dosing of buprenorphine treatment, with induction only initiated when scores indicate moderate to severe withdrawal (COWS >8) to prevent precipitated withdrawal 1. The scale also provides objective monitoring during opioid tapering protocols 1.
Serial assessments should be performed every 1-2 hours during active withdrawal management, allowing real-time dose adjustments 1. Peak withdrawal symptoms typically occur 48-72 hours after last opioid dose and resolve within 7-14 days 3, 1.
Alternative: Subjective Opiate Withdrawal Scale (SOWS)
The SOWS is a 16-item patient self-rated scale where individuals rate symptom intensity from 0 (not at all) to 4 (extremely) 3, 4. Scoring ranges: 4-22 (mild), 23-44 (moderate), 45-64 (high) 3. While useful for patient self-monitoring, COWS remains the objective standard for clinical decision-making 3.
Critical Distinction
Do not confuse COWS with CIWA (Clinical Institute Withdrawal Assessment for Alcohol), which is an entirely different scale specific to alcohol or benzodiazepine withdrawal 5. These scales are not interchangeable 5.
Validation and Reliability
COWS demonstrates strong concurrent validity with correlation coefficients of 0.85 when compared to other validated withdrawal scales 6. The tool shows good internal consistency (Cronbach's alpha 0.78) and substantial interobserver agreement between clinicians and nurses (weighted kappa 0.65) 6, 7. A clinically meaningful increase in withdrawal severity is defined as a change of 6 points (12% maximum percent effect) on COWS 8.