Interpreting Urine Drug Tests: Prevalence of Morphine Metabolism to Hydromorphone in Chronic Pain Patients Treated with Morphine

doi:10.1111/j.1526-4637.2007.00354.x

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Wiley InterScience

Pain Medicine

Volume 9 Issue 7, Pages 918 - 923

Published Online: 28 Aug 2007

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Interpreting Urine Drug Tests: Prevalence of Morphine Metabolism to Hydromorphone in Chronic Pain Patients Treated with Morphine

Ajay D. Wasan, MD, MSc,*^† Edward Michna, MD, JD,* David Janfaza, MD,* Shelly Greenfield, MD, MPH, ^‡ Christian J. Teter, PharmD, ^§ and Robert N. Jamison, PhD*^†

*Department of Anesthesiology, Perioperative and Pain Medicine and ^† Department of Psychiatry, Brigham and Women's Hospital, Harvard Medical School; ^‡ Department of Psychiatry, McLean Hospital, Harvard Medical School; ^§ School of Pharmacy, Northeastern University, Boston, Massachusetts, USA

Correspondence to Ajay D. Wasan, MD, MSc, Pain Management Center, 850 Boylston St, Suite 320, Chestnut Hill, MA 02467, USA. Tel: 617-732-9579; Fax: 617-732-9050; E-mail: awasan@partners.org.

KEYWORDS

Urine Drug Testing • Interpretation • Morphine • Hydromorphone • Metabolism

ABSTRACT

Objective. Pain medicine practitioners frequently use urine drug testing (UDT) to monitor adherence to opioid therapy. It can be difficult to interpret a result as normal or abnormal in relation to which opioid compounds are expected to be found in the urine. We investigated whether hydromorphone may be a metabolite of morphine normally appearing in UDT of patients prescribed morphine.

Design. This is a retrospective case-control study of urine toxicology results in pain patients taking only morphine. Inclusion criteria included urine results positive for morphine only (controls) or morphine and hydromorphone (cases). Demographic and medical history variables, and any history of aberrant drug behavior were recorded and related to the presence or absence of hydromorphone in the urine.

Results. Hydromorphone was present in 21 of 32 cases (66%), none of whom had a history of aberrant drug behavior. Positive cases occurred more frequently in women, in those taking higher daily doses of morphine, and in those with higher urine morphine concentrations (P < 0.05). Only morphine urine concentration was a significant predictor of the hydromorphone metabolite in a logistic regression model (P < 0.05).

Conclusions. Hydromorphone is likely a minor metabolite of morphine, normally appearing in the UDT of patients taking morphine. This finding assists in determining whether a UDT result is normal or abnormal, and subsequently whether a patient is compliant with opioid therapy. This observation should be confirmed by a prospective study in a controlled environment. Variables such as gender, morphine dose, morphine urine concentration, and genetic determinants of morphine metabolism should be investigated further.

DIGITAL OBJECT IDENTIFIER (DOI)

10.1111/j.1526-4637.2007.00354.x About DOI