Clinical Opiate Withdrawal Scale (COWS)

Assesses withdrawal symptoms severity after therapy with opioid medication.

There is more information on the items in the scale and its withdrawal symptoms classification below the tool.

The Clinical Opiate Withdrawal Scale confidently measures already developed physical dependence on opioids based on clinical, objective and subjective data, extracted during an assessor administered session. 

It can be used for one-time assessment or monitoring in time and is available in Appendix 2 of the National Guidelines for Medication-Assisted Treatment of Opioid Dependence.

The COWS scores are included in 5 withdrawal severity classes.

Scores below 5 are not conclusive of any relevant withdrawal symptoms.

Scores between 5 and 36 are indicative of mild (5-12), moderate (13-24) and moderately severe (25-36) withdrawal.

Scores above 36 are consistent with severe withdrawal symptoms.

Was originally aimed at evaluating withdrawal treatment with buprenorphine induction. Has also been validated against CINA as measure for acute opiate withdrawal.


Resting Pulse Rate (bpm)




Restlessness observation during assessment


Pupil size


Bone or joint aches


Runny nose or tearing


GI Upset


Tremor observation of outstretched hands


Yawning observation during assessment


Anxiety or irritability


Gooseflesh skin

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Scale items

The clinical opiate withdrawal scale (COWS) consists of 11 items, as described in the following lines:

■ Resting Pulse Rate (bpm) – measured after the patient has been lying down for at least 60 seconds;

■ Sweating – present and not caused by room temperature or patient activity in the last 30 minutes;

■ Restlessness observation during assessment – observation of inability to sit still;

■ Pupil size – measures degree of dilatation;

■ Bone or joint aches – when attributed to opiate withdrawal not to other comorbidities;

■ Runny nose or tearing – when present without any cold symptoms or allergies;

■ GI Upset – present during the last 30 minutes, not caused by other comorbidities;

■ Tremor - observation of outstretched hands;

■ Yawning observation during assessment – number of yawns during the observation period;

■ Anxiety or irritability – either one or both experienced;

■ Gooseflesh skin – present with or without piloerection.

This is a scale that needs to be administered and scored by a medical professional. It can be used both for one-time assessment and monitoring in time and is officially available in Appendix 2 of the National Guidelines for Medication-Assisted Treatment of Opioid Dependence.


COWS interpretation

After the number of points from the above items are summed, the final score is classified under one of the 5 stages of opiate withdrawal severity, presented in the table below:

COWS result Withdrawal severity
< 5 None/ No relevant symptoms
5 - 12 Mild
13 - 24 Moderate
25 - 36 Moderately severe
> 36 Severe

This means that 5 is the cut off between no withdrawal symptoms experienced, therefore, no addiction likely, and withdrawal symptoms present.

At the other end of the results scale, 36 points is the cut off between moderately severe and severe withdrawal.


About the original study

The study originated as a mean to monitor patient evolution in the withdrawal treatment with buprenorphine induction. Currently it is used in various clinical settings, from opioid detox to chronic pain management.

To show spontaneous opioid withdrawal symptoms, the patient must be physically dependent and have undergone a relative abstinence of opioids.

Validation has reinstated its use as a valid measure for acute opiate withdrawal.

One of COWS main benefits is that it combines clinical, objective and subjective data, extracted from measurements and observation, thus increasing the evaluation accuracy. But as with any tool of this kind, clinical judgment takes the final decision.

Donald R. Wesson, MD, is a board-certified psychiatrist, has served as chief psychiatrist at the Haight-Ashbury Free Medical Clinic in San Francisco and is now in the California Society of Addiction Medicine.


Other opioid assessments

Here are some other examples of tools used in practice:

■ The Diagnosis, Intractability, Risk, Efficacy (DIRE) evaluates long term opioid therapy abuse risks;

■ The Opioid Risk Tool (ORT) predicts opioid addiction risk based on personal and family history of alcohol or drug use;

■ The Substance Abuse Potential (SISAP) enquires about personal substance abuse history to establish potential risks.


Original reference

Wesson DR, Ling W. The Clinical Opiate Withdrawal Scale (COWS). J Psychoactive Drugs. 2003; 35(2):253-9.

Validation study

Tompkins DA, Bigelow GE, Harrison JA, Johnson RE, Fudala PJ, Strain EC. Concurrent validation of the Clinical Opiate Withdrawal Scale (COWS) and single-item indices against the Clinical Institute Narcotic Assessment (CINA) opioid withdrawal instrument. Drug Alcohol Depend. 2009; 105(1-2):154-9.

Specialty: Toxicology

Objective: Assessment

Type: Scale

No. Of Items: 11

Year Of Study: 2003

Abbreviation: COWS

Article By: Denise Nedea

Published On: March 16, 2017

Last Checked: March 16, 2017

Next Review: March 10, 2023