The effects of collection methods on oral fluid codeine concentrations

The use of a variety of alternative biological specimens such as oral fluid for the detection and quantitation of drugs has recently been the focus of considerable scientific research and evaluation. A disadvantage of drug testing using alternative specimens is the lack of scientific literature describing the collection and analyses of these specimens and the limited literature about the pharmakonetics and disposition of drugs in the specimen. Common methods of oral fluid collection are spitting, draining, suction, and collection on various types of absorbent swabs. The effect(s) of collection techniques on the resultant oral fluid drug concentration has not been thoroughly evaluated. Reported is a controlled clinical study (using codeine) that was designed to determine the effects of five collection techniques and devices on oral fluid codeine concentrations. The collection techniques were control (spitting), acidic stimulation, nonacidic stimulation, and use of either the Salivette(TM) or the Finger Collector (containing Accu-Sorb(TM)) oral fluid collection devices. Preliminary data were collected from two subjects using the Orasure® device. The in vitro drug recovery was also evaluated for the Salivette and the Finger Collector devices. With the exception of a single time point, codeine concentrations in specimens collected by the control method (spitting) were consistently higher than concentrations in specimens collected by the other methods. The control collection concentrations averaged 3.6 times higher than concentrations in specimens collected by acidic stimulation and 1.3 to 2.0 higher than concentrations in specimens collected by nonacidic stimulation or collection using either the Salivette or the Finger Collector devices. When calculated using oral fluid codeine concentrations from the clinical study, the elimination rate constant, t( 1/2 ), AUC and the peak oral fluid concentrations demonstrated device difference. The slope of the elimination curve for codeine using the acidic collection method exceeded that of the other four methods. As a result, the t( 1/2 ) for the acidic method was significantly less than that of the control method (1.8 vs. 3.0 h, respectively). Oral contamination contributed to the control method having higher AUC than that calculated using the other methods. There was considerable variation in peak codeine concentrations between devices and between individuals within each collection method. When samples were collected simultaneously with the Salivette and the Finger Collector, the mean codeine concentrations were similar. We were able to recover ≥ 500 μL of oral fluid from 81.8% of the clinical samples collected with the Salivette. However, we were able to recover this volume from only 25.5% of the samples collected with the Finger Collector. In addition, the in vitro drug recoveries were lower using the Finger Collector. When oral fluid was collected nearly simultaneously by the control method and by use of the Salivette, mean control codeine concentrations were 2.3 times higher, but the duration of detection was similar for both methods.