Excretion profile of opiates in dependent patients in relation to route of administration and type of drug measured in urine with immunoassay

Abstract

It is accepted that opiates are detectable in urine within three days from the last dose at a cut-off value of 300 ng/mL. In our clinical practice, some patients tested positive for morphine even after a week of detoxification. The present study evaluates the time course of opiate excretion in urine of dependent subjects (F11.25 according to ICD-10) in relation to route of administration and a kind of street heroin. The group comprised 71 men treated for opiate dependency: 33 of them used heroin exclusively by inhalation; 26 i.v.; 12 used i.v. homemade poppy straw decoctions. Opiate levels were measured once a day by fluorescence polarization immunoassay (TDx Abbott). Detection time ranged from 3 to 10 days for cut-off value 300 ng/mL and from less than one up to seven days for cut-off value 2000 ng/mL. The increases in urine drug concentration that result from changes in urinary output may be mistakenly interpreted as a new drug use. Normalization of drug excretion to urine creatinine concentration reduces the variability of drug measurement attributable to urine dilution. The time function of creatinine normalized opiate concentration has a log-linear character, and decreases at a rate of 2.5 per day on average. New "normalized" cut-off values were proposed: 225 ng/mg creatinine, 1500 ng/mg creatinine, and 3750 ng/mg creatinine that corresponds to 300 ng/mL urine, 2000 ng/mL urine, and 5000 ng/mL urine.