High-Performance Liquid Chromatographic Study of Codeine, Norcodeine, and Morphine as Indicators of Codeine Ingestion

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1 Journal of Analytical Toxicology, Vot, 8, March/ApriL 1984 High-Performance Liquid Chromatographic Study of Codeine, Norcodeine, and Morphine as Indicators of Codeine Ingestion Bill L. Posey and Sydney N. Kimble Pathological and Clinical Services P.O. Box 11866, 2111 East Dakota, Fresno, California Abstract A simple quantitative method for determining codeine, norcodeine, and morphine In urine by high-performance liquid chromatography (HPLC) is described. Urine samples are hydrolyzed and extracted through differential ph extraction. The subsequent use of HPLC allowed separation and quantitation on a reverse phase system with ultraviolet detection. A comparison study of the concentrations of single and therapeutic doses of codeine in urine over a period of time showed that morphine, the major metabollte, increases In proportion to codeine, eventually surpasses the codeine level, and remains higher for the duration of time that the drugs are detectable. Introduction Urine opiates are regularly monitored in emergency room situations, in methadone treatment programs, in probation settings, in the armed forces, and in drug related cases from coroners' offices. A positive result for opiates can have serious medical and legal implications in any of these cases. In order to determine the nature of the opiate used and unequivocally prove its presence, several analytical approaches must be used to verify positive results. In previous reports, various chromatographic systems and immunoassays have been used for the analysis of opiates. Thinlayer chromatography (TLC) and gas-liquid chromatography (GLC) screening and confirming methods have been described (1-3). The widespread use of radioimmunoassay (RIA) stems from a report on the routine screening of urine for morphine by RIA (4). Opiate RIA plays only a screening role since the antibody is not specific for one drug but cross-reacts with the primary opiate and its metabolites. A morphine antibody will bind both morphine and codeine and their glucuronides. Since morphine, the active metabolite of codeine and heroin, is excreted in urine, there is a need for an accurate, sensitive confirmatory method to separate the opiates involved. Methods such as electron-capture G LC (EC/G LC) have been used to confirm morphine in urine samples from patients receiving methadone, and comparison has been made between positive results by TLC, RIA, and EC/GLC (5). A second method, with high-performance liquid chromatography (HPLC), used ion-pair/hplc which separated morphine and two metabolites (normorphine and morphine-3-glucuronide), and tentatively identified morphine-6-glucuronide in urine from morphine-treated cancer patients (6). This report describes urine opiate confirmation by HPLC after R1A screening. The conditions of analysis are similar to those described previously (7), with modifications in sample and chromatographic manipulation. The technique is capable of simultaneously determining the presence and providing a quantitative analysis of codeine, norcodeine, and morphine in urine. Although blood samples are definitive in terms of opiate use and are the specimen of choice, law enforcement officials in some areas prefer to submit urine samples. Urine samples indicate that an opiate is present, but interpretation of the results has been confusing. With only urine as evidence, it becomes necessary to distinguish between a positive codeine result when codeine is ingested and a positive morphine result, which is usually regarded as heroin or morphine abuse. If both are present, it is difficult to state whether single or multiple opiate use has occurred because morphine is a codeine metabolite. In an attempt to distinguish codeine usage, it was necessary to initiate a study to reveal any trends conclusive of codeine ingestion. A comparative study follows that gives concentrations of codeine and its metabolites, norcodeine and morphine, in urine after codeine ingestion. The samples were analyzed by HPLC during the time period that the urine screening results were positive by RIA. Experimental Instrumentation Throughout these studies a Perkin Elmer Series 2 HPLC equipped with a Perkin Elmer LC65T variable-wavelength detector was used. The recorder, which routinely monitored the separation profile at a chart speed of 0.5 cm/min, was a Hewlett- Packard 5880A series GC Terminal, level four. The reversephase chromatographic column used was a Sprint Phase Sep'n Spherisorb-CN (5p.m), 15 cm 4.6 mm i.d., packed by Analytical Sciences. It was mounted in the oven and the column temperature maintained at 40~ The column was eluted with a 68 Reproduction (photocopying) of editorial content of this journal is prohibited without publisher's permission

2 mobile phase of methanol:phosphate buffer, 0.05M (40:60 v/v), at a ph of 6.8 and a flow rate of 1.5 ml/min. The pressure was 2400 psi. The column effluent was monitored at 210 nm at attenuations ranging from 1 2' to 28 depending on the concentration of the analyte in the urine sample being analyzed. Reagents All solvents and chemicals were analytical grade. The solvents were obtained from Burdick and Jackson Laboratories, and chemicals were purchased from Mallinckrodt. Water for aqueous solutions was deionized and purified using Norganic trace organic removal cartridges by Millipore. fl-glucuronidase (Sigma No. G-0251) was diluted with water for a concentration of 20,000 Fishman units/ml. Sodium acetate buffer, I. IM, was prepared by dissolving g of sodium acetate in water, adding 22 ml glacial acetic acid, and further diluting to a total volume of 1 L with water for a ph of 5.2. Dibasic potassium phosphate (40%) buffer was made with 400 g of K2HPO4 in 1 L water. The extracting solvent was a combination of chloroform: isopropanohheptane (50:17:33 v/v). The mobile phase consisted of 40~ methanol and 60~ phosphate buffer. Buffer was prepared by mixing equal portions of 0.05M KH2PO, (6.8 g/l) and 0.05M K2HPO, (8.7 g/l) to give a final ph of 6.8. The eluate was filtered through a 0.22-/~m (pore size) Millipore filter for mixing, degassing, and removing particulate matter. Standards The opiates (codeine, norcodeine, and morphine) were purchased from Applied Sciences. Stock solutions were separately prepared for each drug in methanol to give a concentration of 50 mg/dl in terms of free base. A working standard of codeine, norcodeine, and morphine was made by 50-fold dilution of the stock standards: 0.1 ml of each stock standard was combined and diluted to 5 ml with drug-free human urine to result in a 10-mg/L concentration of each opiate in a single standard. Urine calibration standards were made by further diluting the working standard to give final drug concentrations of 0.2, 0.5, and 2.0 mg/l. The internal standard (IS) Nalorphine HCI, purchased from USP Reference Standards, was diluted with methanol to provide a working solution with a nalorphine concentration of 50 mg/l. The urine control was morphine-3-glucuronide reinforced urine at a concentration of 2 mg/l. The 10 mg/l urine working standard, urine morphine-3-glucuronide control, and the diluted/3-glucuronidase were stored at - 20~ in 2-mL aliquots in conical glass tubes with Teflon-lined screwcaps. Stability was approximately 3 months. Screening Procedure Abuscreen Radioimmunoassay for Morphine ('251) was used for screening purposes. The kit was obtained from Roche Diagnostics, Hoffman LaRoche, and used according to the manufacturer's protocol with half-volumes of the reagents and full volume of the specimen. Codeine and morphine react similarly with the morphine-specific antibody and, as such, the screening procedure was evaluated as opiates positive by RIA. The lowest concentration set for detection of opiates by RIA was rag/l, the same as the kit positive control value. Any urine screen less than the positive control value was considered to be negative for opiates. Positive screens were further evaluated by HPLC analysis in which quantitations for codeine, norcodeine, and morphine were performed. Confirmation and Quantitation Procedure Urine specimens were extracted directly to determine the free opiates. They were also incubated with fl-glucuronidase in order to hydrolyze opiate glucuronides and determine total opiates. Two milliliters of urine were added to 0.4 ml (I.1M) acetate buffer, ph 5.2, and 0.5 ml fl-glucuronidase (10,000 Fishman units) in a 15-mL screwcap glass tube. The acidic urine was vortex-mixed and the tube incubated overnight in a 56~ waterbath. Both urine standards and the urine morphine-3-glucuronide control were processed along with the samples. After cooling, the urine was basified or, if the urine was to be extracted directly, the fl-glucuronidase step was omitted and the urine basified. To the tube was added 2.0 ml of 4007o K2HPO,, ph 9.2, and 0.05 ml 3.5M NaOH along with 0.05 ml of nalorphine, 50 rag/l, which was used as IS. After adding 10 ml extraction solvent, the tube was capped, mechanically shaken 10 min, and centrifuged for 5 rain at 2000 rpm. The upper organic layer was transferred to a clean tube and back-extracted with 5 ml of 0.2M HC1. The tube was mixed and centrifuged again; the solvent phase was discarded and the acid-aqueous phase retained and washed with 2.0 ml heptane. The acidaqueous phase was then basified with 2 ml 40% K2HPO, and 0.5 ml concentrated NH,OH and further extracted with 8 ml chloroform. The mixture was mixed vigorously, centrifuged, and the aqueous layer discarded by vacuum aspiration. The chloroform extract was transferred to a clean round-bottom tube and the solvent was evaporated to dryness under a stream of air while the tube was in a 56~ water bath. The residue was reconstituted in ml of mobile phase and 10/~L were injected into the liquid chromatograph. Calculations Codeine, norcodeine, and morphine standards of known concentration were analyzed along with the IS for each set of urine A ~ B c S 4 6 t Time (,~'{ n ) (' 4 6 Figure 1. Typical HPLC chromatograms of drug-free human urine processed through entire assay procedure: (A) urine specimen containing 2.5 ~g nalorphine IS; (B) urine specimen (2 ml) calibration standard with a concentration of 0.5 mg/l for codeine, morphine, norcodeine, and IS; (C) urine specimen from volunteer receiving codeine, sample collected 32 hr after single 30-mg oral dose of codeine, codeine=0.17 mg/l and morphine=0.39 mg/l. 69

3 Journal of Analytical Toxicology, VoL 8, March/April 1984 specimens. The criterion for identification was that all four compounds must be at their correct retention time after separation on the chromatographic column. The drugs in the urine samples were identified by direct comparison of the retention times of peaks representing codeine, norcodeine, morphine, and nalorphine with those of the compounds in the standard. After the qualitative identity was established, quantitation was made by comparing the peak height ratios derived from the measurement of the peak height of the compound divided by the peak height of IS for the standard vs. the urine sample. Models for Study Group I included 5 volunteers who ingested one tablet of codeine-containing analgesic (30 mg codeine) every 4 hr for five doses. Ten hours after the last dose, sampling began. Urine was collected as a timed sample every 4 hr for approximately 82 hr (or at least until a negative RIA opiate screen was produced). Each urine was screened and extracted. The levels of codeine and its major metabolites, norcodeine and morphine, were determined by HPLC analysis. Group 2 included 5 volunteers who received a single oral dose of codeine-containing analgesic (30 mg codeine). After 12 hr, urine samples were collected in the same manner and analyzed by the same methodology. to fall within the stated levels before repeat analysis. Samples from a single urine specimen containing morphine-3- glucuronide were analyzed I l times over a period of 6 months for between-run precision measurements. The urine control had a weighed-in value of morphine-3-glucuronide at a level of 2 mg/l. However, since only 60~ of that concentration was morphine, a theoretical value of 1.2 mg/l morphine was the concentration set for the control after hydrolysis. With ~-glucuronidase treatment, 96~ of the morphine conjugate was converted to morphine. On 11 replicates, the mean value determined was 1.15 mg/l with a standard deviation of _ mg/l and coefficient of variation of 9.2~ The morphine level was calculated from calibration curves prepared from extracted standards and, therefore, do not represent absolute recovery values. All of the drugs were reproducibly measured at a concentration of 50 #g/l in urine. With use of the IS to correct for extraction variables and injection volumes, the sensitivity of the procedure was estimated to be 25 ~g/l, the lower limit of detection set for this study. Drugs of abuse such as cocaine, diazepam, methadone, amphetamine, phencyclidine, and meperidine did not interfere with the compounds of interest when samples containing these drugs were analyzed by this procedure. Drug-free urines gave negative results after extraction and analyses. No peaks with retention Results and Discussion Analytical Variables. Figure 1 depicts chromatograms of the separation of codeine, norcodeine, morphine, and the IS. Blank urine, Figure I A, shows only IS and that the extraction procedure removed interfering endogenous peaks. Figures 1B and IC show the resolution of the IS, the parent compound, and the metabolites in a urine-based calibration standard and in a sample from a volunteer taking a codeine-containing analgesic. Calibration curves obtained by analyzing urine samples reinforced with codeine, norcodeine, and morphine in the concentration range of 0.2, 0.5, and 2.0 mg/l were subjected to linear regression analysis. Table I shows that the statistics generated from least squares analysis of the data collected from 6 calibration curves indicated linearity and reproducibility of the assay in the chosen concentration range. Figure 2 shows plots obtained from the mean peak ratios vs. concentration for the 6 calibration curves of each drug. Each set of calibration curves was prepared for a different run on a different day. Urine specimens determined to be higher than the highest standard were diluted._o -f Q ~2 codeine Ix), norcodeine 1 and morphine (&) O0 i 2 i i i ~ i I I I 110 i i i i i i J i 210 i mg/l Figure 2. Drug/IS peak height ratio vs. urine drug concentrations after HPLC analysis of reinforced urine standards of codeine, norcodeine, and morphine (average of 6 determinations). Table I. Statistical Data Collected from Six Calibration Curves: Linear Regression Analysis Codeine Norcodetne Morphine Correlation y- Correlation y- Correlation y- Run Coefficient Intercept Slope Coefficient Intercept Slope Coefficient Intercept Slope , , ,

4 times the same as codeine, norcodeine, and morphine have been identified. Opiates and metabolites such as morphine-3-glucuronide, normorphine, diacetylmorphine, 6-momoacetylmorphine, hydromorphone, and hydrocodone were also checked and found not to interfere (7). During examination of urine samples obtained after codeine ingestion, quantitation was performed in two ways. First, a direct determination of free (unbound) codeine and morphine was made. Second, portions of the urine samples underwent /3-glucuronidase hydrolysis in which the conjugated opiates were released and determination of total (free plus bound) codeine and morphine was made. The results of the procedure for direct extraction were compared to those after enzyme hydrolysis. The free fraction of codeine and morphine as determined in a volunteer is shown in the distribution graph, Figure 3. The combined amount of codeine plus conjugate is superimposed and shown as the total amount at 4 to 8 hr intervals. The same is shown for morphine and its conjugate. Both codeine and morphine excreted in conjugated form (bound as glucuronides) could be detected over a longer period of time following hydrolysis. Screening by RIA, with sensitivity set at 0.3 mg/l and including free and conjugated opiates, gave a negative result after 58 hr. With hydrolysis, the total codeine and morphine levels were also measured for 58 hr. After 10 hr, free codeine and morphine would not be confirmed by less sensitive methods and, after 24 hr, free morphine would not be confirmed by HPLC. Because codeine is excreted in urine unchanged and conjugated, or as its unconjugated and conjugated metabolites, it is necessary to perform a hydrolysis step to track the levels of opiates as they are eliminated from the system after the drug is received orally. Comparative Study of Codeine in Human Urine Two studies demonstrate the pattern of elimination of codeine and its metabolites: one after a therapeutic regimen of 5 doses and one after casual use of I dose. Analysis of urine samples collected from volunteers every 4 hr after receiving codeine showed that codeine, norcodeine, and morphine are detected and that, prior to negative results by RIA screening, morphine levels are higher than codeine levels. Results indicate that for the first 10 to 20 hr the ratio of codeine to morphine is > 1 and between 20 to 40 hr an inversion occurs and the ratio of codeine to morphine is < I. Two studies were undertaken to see if values are significantly different between two groups or if the pattern of elimination deviates. Variability did occur in levels and time periods, but a consistent overall pattern was found. It has been reported that although both codeine and morphine are detected after taking codeine, TLC chromatograms of a sample 3 days after use show only morphine and are identical to those produced following heroin or morphine use (8). Another report indicates an inversion of codeine to morphine ratios, from ingestion of a single dose of codeine, after only 24 hr (9). With the finding that morphine levels in urine are higher than codeine, it is difficult to ascertain whether codeine by itself or morphine derived from heroin with a codeine contaminant has been taken (10). Since a positive result for morphine alone usually represents heroin abuse, it is imperative that positive screening results are properly interpreted. The first study was made to uncover any trends concerning ingestion. Representative graphs from analyses of the urine samples (hydrolyzed) are presented in Figure 4 (A, B, C, D, and E). Urine codeine, norcodeine, and morphine concentrations are plotted vs. time for each of 5 volunteers. Table II shows the results obtained from quantitative analysis of each urine sample until it was found negative by RIA screening. Norcodeine was quantitated in three cases (B, D, and E) with a sensitivity of 50 #g/l until the inversion of codeine to morphine ratio, after which it was not detected. In two cases, A and C, norcodeine was detected for 4 hr after the inversion. The results indicate that norcodeine is present in urine after codeine ingestion and is not detectable at the approximate time of the inversion of codeine to morphine ratio of < 1. Up until 20" 18~ mg/i Codeine Hydrolyzed Conjugate Free Codeine Unchanged Morphine Hydrolyzed Conjugate ::::::::::::::::::::: ~t~ Free Morphine UnconJugatod ~s from last oral dose Figure 3. Distribution levels of codeine and morphine, conjugated and unconjugated, in urine before and after/3-glucuronidase treatment, as determined by HPLC. 71

5 that time, the presence of norcodeine indicates that codeine has been taken as the primary drug, providing that multiple opiate use has not occurred. When total opiates approach I mg/l, unless norcodeine is present, it is very difficult to assign a parent drug. A hypothetical case can be made: An unknown time after use, urine is collected from a suspect said to be a heroin addict. Upon assay, the values are similar to those of Volunteer B at 34 hr, and no assessment can be made about the use of a parent drug; however, if the values are like those of Volunteer A at 34 hr, with norcodeine present, the findings would indicate the probability that only codeine had been taken. After 40 hr, '~1- Figure 4. Patterns of elimination in urine for Volunteers A-E after ingestion of a therapeutic regimen of codeine. Con- I,,. centration (mg/l) is plotted vs. time (hr after last dose) for,ok ~ codeine (x ), morphine (... ), and norcodeine ( I \ Each graph is one semi-logarithmic scale (4 cycles). I \ o~ 1 ~2 ii ~ ~a 2o ~2 ~4 26 ~e ~ e io i~ I. ~6 4S ~ 60 Volunteer A most of the values would give the impression of heroin or morphine use (Table II). As seen from the graphs in Figure 4, the pattern of elimination was essentially the same for all 5 volunteers: the codeine level was the highest at the beginning, the morphine was the highest at the end and, in the middle, an inversion of codeine and morphine took place while norcodeine became undetectable. At one extreme, Volunteer D excreted the opiates quickly and produced a negative screen after approximately 30 hr. Volunteer E, at the other extreme, excreted the opiates slowly and never produced a negative screen in over 60 hr. In order to delineate trends between therapeutic dosage or casual use, the second study was undertaken. Table 111 gives pertinent data concerning time and concentration levels. Overall, the results show the same pattern of elimination. Without the continuing ingestion of codeine and the build up of metabolites with a single dose, the inversion of codeine to morphine ratio to < I did not occur until an average of 30 hr (24 to 40 hr) after codeine use. A negative screen was produced after 40 hr. Similarly, the norcodeine appears and then becomes undetectable about the time of the inversion. Again a hypothetical question is asked: If a driver is stopped 30 to 40 hr after taking a codeine analgesic for a throbbing headache, is the case distinguishable from that of a heroin or morphine user? Results of these analyses are comparable to others which led to the conclusion "that extreme caution should be exercised when drawing conclusions from results of estimations on isolated urine specimens collected over a short period of time" (11). ~o _J E Volunteer B ~6 ~a 20 ~ O ~ ~a 40 ~ ~8 Volunteer D E "... /\~./~ "'--'~,~, \,----./... o o1_ %. b oi iz 14,6 le ~ 3s 40.~ e 50 ~2 5~ ~ 5e 6o Volunteer C ol 12 I~ '6 IS ZO 2~ 2~ 26 2e ~ ~ 40 4~ ~ 46 4~ ~ ~ 6O Volunteer E 72

6 Conclusions The results of the urine analysis of codeine, norcodeine, and morphine indicate that: l. After taking therapeutic oral doses of codeine, morphine can be detected. Definite assignment of ingestion of the parent drug, codeine, becomes very questionable in urine samples when urine total opiates approach a level of 1 rag/l, regardless of the amount of drug taken. 2. Morphine, the major metabolite, increases in proportion to codeine and surpasses the parent drug in concentration 20 to 40 hr after the last ingestion of codeine. 3. Norcodeine is detected in the urine when codeine is ingested and disappears when the ratio of codeine to morphine is inverted, i.e., the levels of morphine are higher than the codeine levels. It may be possible to use the presence of norcodeine as an indicator of definite confirmation for codeine ingestion. 4. Hydrolysis of the urine sample is imperative in the analysis of opiates. Losses of up to 90% codeine and 93~ morphine per sample are indicated when urine is analyzed without a hydrolysis step. 5. Codeine with morphine as a metabolite continues to be excreted in urine for several days. Codeine and morphine were present in detectable quantities in urine at the minimum detectable limit of the screening method. Table II. Codeine and Metabolite Concentrations (mg/l) in Human Urine in Study #1 after Codeine Ingestion of a Therapeutic Regimen of Five Doses from Last Dose Volunteer Opiate NS = No sample NORCODEINE ,028,048 0 A MORPHINE 2, RIA CODEINE (-) NORCODEINE NS B MORPHINE NS RIA CODEINE NS, (-) NORCODEINE , C MORPHINE NS NS , RIA CODEINE ,129 (-) NORCODEINE D MORPHINE RIA CODEINE (-) NORCODEINE MORPHINE , CODEINE 35, ,337 Table III. Codeine and Metabolite Concentrations (mg/l) in Human Urine in Study #2 after Codeine Ingestion of One Dose from Last Dose Volunteer Opiate NORCODEINE, RIA (-) MORPHINE , CODEINE , NORCODEINE , RIA (-) MORPHINE 2, CODEINE , NORCODEINE RIA (-) MORPHINE 2, CODEINE NORCODEINE t,87.619, D MORPHINE , RIA CODEINE , (-) NORCODEINE E MORPHINE RIA CODEINE (-) 73

7 Acknowledgment We thank the volunteers for their contribution to this report. To D.B. Robertson, Cindy kiedstrand and Ken Yoshimune we are indebted for technical assistance. We are grateful to T.C. Nelson, our director, for his support of this project. References 1. J.E. Wallace, J.D. Biggs, and K. Blum. Gas-liquid and thin-layer chromatographic determination of morphine in biologic specimens. Clin. Chim. Acta 36:85 (1972). 2. N.C. Jain, T.C. Sneath, R.D. Budd, et al. Gas chromatographic/thin-layer chromatographic analysis of acetylated codeine and morphine in urine. Clin. Chem. 21: (1975). 3. D. Mathis and R. Budd. GLC/-FLC analysis of codeine and morphine in urine via derivatization techniques. Clin. ToxicoL 16: (1980). 4. D. Catlin, R. Cleeland, and E. Grunberg. A sensitive, rapid radioim- munoassay for morphine and immunologically related substances in urine and serum. Clin. Chem (1973). 5. G. Nicolau, G. Van Lear, B. Kaul, et al. Determination of morphine by electron capture gas-liquid chromatography. Clin. Chem. 23: (1977). 6. J.O Svensson, A Rane, J. Sawe, et al. Determination of morphine, morphine-3-glucuronide and (tentatively) morphine-6-glucuronide in plasma and urine using ion-pair high performance liquid chromatography. J. Chromatogr. 230: (1982). 7. B.L. Posey and S.N. Kimble. Simultaneous determination of codeine and morphine in urine and blood by HPLC. J. Anal. Toxicol. 7: (1983). 8. M.D. Solomon. A study of codeine metabolism. Clin. Toxicol. 7: (1974). 9. S. Goenechea and H. Brzezinka. Morphinnachweis im ham nach einnahme von codein. Fresenius' Z. Anal. Chem. 313: (1982). 10. R.C. Baselt. Disposition of Toxic Drugs and Chemicals in Man. 2nd Ed. Biomedical Publications, Davis, California, 1982, p D.E. Fry, P.D. Wills, and R.G. Twycross. The quantitative determination of morphine in urine by gas-liquid chromatography and variations in excretion. Clin. Chim. Acta 51: (1974). Manuscript received December 6,