Simultaneous hair testing for opiates, cocaine, and metabolites by GC-MS: a survey of applicants for driving licenses with a history of drug use

A sensitive GC-MS method for the simultaneous determination of opiates, cocaine, and metabolites in hair at a cut-off level of 0.1 ng/mg was adopted to assess past exposure to these drugs in applicants for driving licenses with a history of drug use. The sampling protocol consisted of collection of one hair (sample A, 5-cm length) and one urine sample. When hair and urine (EMIT Syva, cut-off levels: 0.3 mg/l for opiates, 0.15 mg/l for cocaine, GC-MS confirmation of positives) were both positive or negative the protocol was concluded. In the other cases, the assessment of 'current exposure' to drugs was carried out, in order to avoid seriated random urinalysis, by collecting a second hair sample (sample B) 6 weeks later and analysing the proximal 1-cm segment. Out of the 214 'A' hair samples analyzed, 14 (6.5%) tested positive for morphine and/or 6-acetylmorphine (6AM), and 26 (12%) for cocaine and/or benzoylecgonine (BE), whereas none of the samples tested positive for both drugs. Levels between 0.1 and 1 ng/mg of the single analytes were found in eight out of the 14 morphine-6AM positives (57%) and in 18 out of the 26 cocaine-BE positives (69%). The time course of positive cases showed a progressive decrease of morphine-6AM positives and a corresponding increase of cocaine-BE positives within the study period September 1995-February 1999. No cases with positive urine and negative hair were observed. Among the 40 positive cases, seven (four and three for opiates and cocaine, respectively) were found to be 'currently exposed to drug', four by urinalysis (three and one) and three by analysis of the hair sample B (1 and 2).     

Correlation of the incidence of cocaine and cocaethylene in hair and postmortem biologic samples

Hair samples are useful as a matrix for drug testing because drugs can be detected in hair for longer periods than in blood or urine. The authors report a prospective comparison of the detection of cocaine and cocaethylene in routine postmortem biologic specimens to the detection of cocaine and cocaethylene in hair. The authors collected hair samples from various areas of the head in 53 autopsy cases, prepared them, and analyzed them by gas chromatography/mass spectrometry (GC/MS) for cocaine and cocaethylene. The authors compared the results of hair analysis with the results of toxicologic analysis performed on routine postmortem samples by enzyme multiplied immunoassay technique and GC/MS. Cocaine was found in either biologic fluids or in hair in 16 of 53 samples tested. Nine samples were positive for cocaine in both biologic fluids and hair. Five samples contained cocaine only in biologic fluids, and two contained cocaine only in hair. Cocaethylene was present in two cases. Drug screening of hair provides additional information in some autopsy cases, but the authors have not made hair analysis a routine practice. It may prove useful to save hair samples in all cases for later analysis if warranted by additional history or autopsy findings.     

Hair testing for drugs of abuse: evaluation of external cocaine contamination and risk of false positives.

In some laboratories hair testing may be the main method for the evaluation of individual's drug history, however, compelling evidence supports the possibility that the presence of a small amount of drug in hair can derive from external contamination. The aim of the present study is to verify if a single external contamination with a small amount of cocaine will last sufficiently long to make a contaminated subject indistinguishable from active users, and if normal washing practices together with the decontamination procedures are sufficient to completely remove the external contamination. The results obtained using the decontamination methods suggested in literature demonstrate that significant concentrations of cocaine (>1 ng/mg) and moderate quantities of benzoylecgonine (generally <0.5 ng/mg) are still detectable up to 10 weeks after contamination. These results question the reliability of hair testing. In fact, even using the most sophisticated decontamination procedures it is not possible to distinguish a drug-contaminated subject from an active user. Thus, while a negative result excludes both chronic use and "contact" with drugs, a positive result cannot and must not be interpreted as a sure sign of drug addiction, but should be further confirmed by urine analysis.     

Hair analysis of opiates in mothers and newborns for evaluating opiate exposure during pregnancy

The increasing interest in toxicological hair analysis as a marker of human exposure to xenobiotics such as illicit substances or therapeutic drugs, has been made feasible by the extension of mass spectrometry, a highly sensitive method of detection. A newborn exposed to drugs in utero can suffer from a varying degree of withdrawal syndrome, a few days after birth. If of opiate origin, the withdrawal syndrome can be treated with morphine, among other therapeutics, but it is not easy to diagnose because of atypical symptoms presented by neonates and especially when maternal drug addiction has not been revealed. To assess and measure toxicological factors linked with the appearance and the severity of this syndrome, maternal and neonatal matrices such as urine, meconium and hair were collected during a protocol approved by the ethical committee. Opiates in particular were measured with GC-MS and potential combined dependences (cannabis, cocaine, amphetamine, LSD and benzodiazepines) and/or substitutive therapeutics (methadone or buprenorphine) were also assessed in 17 mother/neonate couples. Gestational opiate exposure profiles were drawn up and linked with the observed withdrawal syndromes. A withdrawal syndrome seems to appear more frequently after foetal exposure to an association of opiates/substitutive molecules (8 out of 10 withdrawal syndromes observed in this study), although the impact of cocaine and benzodiazepines must also be taken into account. The results obtained in neonatal hair make it possible to affirm foetal drug exposure and are in accordance, for the majority, with the appearance of a neonatal withdrawal syndrome (NWS). Neonatal hair analysis could contribute to assess in utero exposure to opiates, particularly when results in urine and meconium are negative or when these matrices are not available.     

Hair analysis for drugs of abuse. Hair color and race differentials or systematic differences in drug preferences?

There is currently a debate in the literature on chemical drug analysis concerning the contribution of biophysical attributes associated with specimens and specimen donors to assay outcome. In recent years this debate has focused on hair analysis, but has in the past also been raised in urinalysis interpretation. In this article we examine several aspects of that controversy. First, we present data regarding the effects of hair color on the distribution of positive hair testing results for three drug classes. We compare these results to negative hair samples from comparable donors. This data is derived from head hair from preemployment donors that was classified according to seven visual color categories. We determined the distribution of colors for hair samples devoid of any of three assayed drugs (amphetamines, cocaine, and cannabinoids). Subsequently, this distribution was compared with the distributions for hairs that had tested positive for amphetamines, cocaine or cannabinoids. We examined a total of 2000 randomly selected samples; 500 negative hair samples and 500 positive samples for each of three drugs: cannabinoids, cocaine, and amphetamine. We also evaluated ethnic/racial factors in relation to positive urinalyses for various ethnic/racial groups. We examined approximately 4000 urine specimens from two different groups, each constituting around 2000 specimens. In addition to ethnicity/race and urinalysis outcome, we also examined the relationship between the hair color distributions of urine donors and the corresponding urinalysis results for the three drug classes. We also compared them to drug-negative samples. Our summary impression is that the observed outcome patterns were largely consistent with differences in drug preferences among the various societal groups. There was little evidence of a pattern attributable to hair color bias alone or selective binding of drugs to hair of a particular color. Likewise, there was no discernible pattern associated with race or ethnicity that would lend support to a "race effect" in drug analysis.     

General unknown screening in hair by liquid chromatography-hybrid quadrupole time-of-flight mass spectrometry (LC-QTOF-MS)

The retrospective investigation of the exposure to toxic substances by general unknown screening of hair is still a difficult task because of the large number of possible poisons, the low sample amount and the difficult sample matrix. In this study the use of liquid chromatography-hybrid quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) was tested as a promising technique for this purpose. In the optimized procedure, 20mg hair were decontaminated with water and acetone and two times extracted by 18h incubation with 0.5ml of a mixture of methanol/acetonitrile/H(2)O/ammonium formate at 37°C. A mixture of deuterated standards from different drug groups was added for quantification and method control. The united extracts were evaporated to a residue of 0.5ml and 5μl were injected without clean-up for LC-QTOF-MS measurement (instrument Agilent 6530) with positive electrospray ionization and in data dependent acquisition mode. For peak identification the accurate mass data base and spectral library of the authors was used which contains accurate mass CID spectra of more than 2500 and theoretically calculated accurate mass data of more than 7500 toxicologically relevant substances. Validation at the example of 24 illegal drugs, their metabolites and benzodiazepines resulted in limits of detection of 0.003-0.015ng/mg, and limits of quantification of 0.006-0.021ng/mg with good accuracy and intra- and interday reproducibility. The matrix effect by ion suppression/enhancement was 72-107% for basic drugs and 42-75% for benzodiazepines. Yields of the hair extraction above 90% were determined for 59 drugs or metabolites. The method was applied to hair samples from 30 drug fatalities and from 60 death cases with known therapeutic drug intake at life time. Altogether 212 substances were identified with a frequency per drug of 1-40 (mean 4.2) and per case of 2-33 (mean 10.2), between them 35 illegal drug related substances and 154 therapeutic drugs. Comparison with the data known from case histories and from the analysis of blood, urine and gastric content showed only a low agreement, with many unexpected drugs detected and many reported drugs not detected in hair. Basic drugs and metabolites such as opioides, cocaine, amphetamines, several groups of antidepressants, neuroleptics, beta-blockers or the metamizole metabolite noramidopyrine were found with high frequency whereas acidic and several neutral drugs such as cannabinoids, salicylic acid, furosemide, barbiturates, phenprocoumone or cardiac glycosides could not be detected with sufficient sensitivity, mainly because of the low ion yield of positive ESI for these compounds. The advantage of a comprehensive acquisition of all substances is paid by a lower sensitivity in comparison to targeted screening LC-MS/MS procedures. In conclusion, the procedure of sample preparation and LC-QTOF-MS analysis proved to be a robust and sensitive routine method in which the qualitative screening for a wide variety of toxic substances in hair is combined with the quantitative determination of selected illegal drugs.     

Hair analysis for driving licence in cocaine and heroin users. An epidemiological study

Diagnosis of drug exposure is strongly supported by analysis of hair samples. In the province of Brescia, Italy, for regranting driving license to drug addicts or occasional abusers, a control programme was adopted including analysis of illicit drugs in two hair segments (0-3 and 3-6 cm) and in urine. From January 1998 to April 1999, upon request of the Local Medical Commission, 697 hair samples were tested in our laboratory. One hundred and eighty subjects resulted positive in hair for one or two of the controlled drug classes (73.3% for cocaine, 10% for opiates, 16.7% for both). Positive subjects were classified by residence, age, sex and license category. Seventy-two subjects were called back after 6-12 months and submitted to a second hair and urine analysis: in 34 cases the result of the first analysis was confirmed (19 negatives, 15 positives for one or both drug classes). Another 37 cases tested positive at the first control and negative at the second, suggesting the hypothesis that a strict control may have a significant deterrent function. The high percentage of negative results at the second control may be explained by the prevalence of cocaine users in the examined population. Our results allow us to conclude that the strict application of control rules lead to a decrease of social risk behaviours.     

Results of hair analyses for drugs of abuse and comparison with self-reports and urine tests

Urine as well as head and pubic hair samples from drug abusers were analysed for opiates, cocaine and its metabolites, amphetamines, methadone and cannabinoids. Urine immunoassay results and the results of hair tests by means of gas chromatography-mass spectrometry were compared to the self-reported data of the patients in an interview protocol. With regard to the study group, opiate abuse was claimed from the majority in self-reports (89%), followed by cannabinoids (55%), cocaine (38%), and methadone (32%). Except for opiates the comparison between self-reported drug use and urinalysis at admission showed a low correlation. In contrast to urinalysis, hair tests revealed consumption in more cases. There was also a good agreement between self-reports of patients taking part in an official methadone maintenance program and urine test results concerning methadone. However, hair test results demonstrated that methadone abuse in general was under-reported by people who did not participate in a substitution program. Comparing self-reports and the results of hair analyses drug use was dramatically under-reported, especially cocaine. Cocaine hair tests appeared to be highly sensitive and specific in identifying past cocaine use even in settings of negative urine tests. In contrast to cocaine, hair lacks sensitivity as a detection agent for cannabinoids and a proof of cannabis use by means of hair analysis should include the sensitive detection of the metabolite THC carboxylic acid in the lower picogram range.     

Comparative investigations on the uptake of basic substances into the human keratinocyte cell line HaCaT--a model for the uptake of xenobiotics into the keratinocytes of the hair follicle

The human cell line HaCaT was used to study drug uptake by keratinocytes as an in-vitro model to elucidate drug incorporation into anagen hair follicle. The basic drugs under investigation were taken up very rapidly resulting in a concentration plateau in the keratinocytes which was dependent on the drug concentration in the cell culture medium. The results obtained for HaCaT clearly demonstrated the existence of a partition-equilibrium between the extracellular and intracellular drug concentrations. Only small amounts of the offered drugs were taken up and remarkable differences were observed showing a decreasing uptake for imipramine > haloperidol > cocaine/benzoylecgonine. Total protein content in the culture medium was 3.5 +/- 0.3 mg/mL and the protein binding of the drugs to the foetal serum proteins was found to be negligible in the experiments. Overall, the in vitro findings were consistent with previous observations for in vivo drug incorporation into hair. In particular, an explanation was found for the correlation between the AUC-value and hair concentration observed in animal studies as well as for the generally low drug concentrations in non-pigmented hair.     

Influence of bleaching on stability of benzodiazepines in hair

In order to study the influence of hair bleaching on benzodiazepines concentrations, hair was treated with a bleaching product (Poly Blonde, Schwarzkopf & Henkel) for 20 min. The treated hair specimen was obtained from a person who died after an overdose of several illicit drugs associated with benzodiazepines. Bleached and non bleached hair were washed (acetone and water), pulverised and then incubated for 2 h in a thioglycolic solution. In the extracts obtained by solid-phase extraction on C18 columns, the different drugs with the corresponding deuterated standards were derivatized and determined by GC-MS in a SIM mode. These results show that the concentrations of all the drug detected decreased in bleached hair in comparison with non treated hair. Whereas the diminution was less important for cocaine and benzoylecgonine (decrease of 24.6 and 36.4%, respectively), concentrations for codeine, 6-monoacetylmorphine and morphine decreased more significantly (decrease of 57.5, 88.6 and 67.4%, respectively) as well as those of diazepam, nordazepam and 7-aminoflunitrazepam (decrease of 39.7, 67.7 and 61.8%, respectively). The results in this study agree with those of other authors that bleaching affects the stability of cocaine and opiates incorporated in hair. These findings also point out that bleaching influences the stability of entrapped benzodiazepines in hair. Finally, these results reconfirm that it is very important to consider the cosmetic history of a hair sample in the interpretation of hair analysis results.     

Disappearance of cocaine from human hair after abstinence

In this work the study of the disappearance of cocaine in hair is reported. The subject of the study is a woman who stopped the consumption of cocaine after a period of drug abuse of over 1 year. Hair samples were collected over a period of 10 months. During this time the absence of cocaine intake was monitored by the toxicological analysis of urine, performed every 2 days. After decontamination with methanol, the hair sample, cut in two segments (0-1.5 and 1.5-3 cm from the hair root) was added with cocaine-D(3) (internal standard), hydrolyzed and extracted with chloroform/isopropanol (9:1). The extract was evaporated to dryness, reconstituted in 25 microl of ethyl acetate and analyzed by GC-MS in SIM mode. The obtained results show that the incorporation of cocaine in hair decreased during the first 3 months after the last consumption and after this period of time no cocaine was found in the hair sections closest to the root.     

Detection of drugs in human hair using Abbott ADx, with confirmation by gas chromatography/mass spectrometry (GC/MS).

The authors suggest use of the fluorescence polarization immunoassay (FPIA) technique in evaluation of chronic drug abuse using human hair. Hair was decontaminated in 5 mL of ethanol for 15 min at 37 degrees C and then incubated in 3 mL of 1M sodium hydroxide (NaOH) for 1 h at 100 degrees C. Afterwards, the aliquots were neutralized and analyzed using Abbott ADx for a negative or positive response for the following drugs: benzodiazepines, barbiturates, antidepressants, opiates, cocaine, amphetamine, and cannabis. All the positive samples were confirmed by gas chromatography/mass spectrometry (GC/MS). Only one false positive was detected (caused by interference of a phenothiazine with the antidepressants kit), clearly demonstrating the capability of ADx for toxicological screening of human hair.     

Experience with urine drug testing by the Correctional Service of Canada

The Correctional Service of Canada implemented a urine drug-screening program over 10 years ago. The objective of this report is to describe the program and drug test results in this program for 1999. Offenders in Canadian federal correctional institutions and those living in the community on conditional release were subject to urine drug testing. Urine specimens were collected at correctional facilities and shipped by courier to MAXXAM Analytics Inc. laboratory. All urine specimens were analyzed for amphetamines, cannabinoids, cocaine metabolite (benzoylecgonine), opiates, phencyclidine, benzodiazepines, methyl phenidate, meperidine, pentazocine and fluoxetine by immunoassay screening (homogeneous EIA and ELISA assays) followed by GC-MS confirmation. Ethyl alcohol was analyzed when specifically requested. Alternative screening and confirmation methods with lower cut-off values were used, whenever urine specimens were dilute (creatinine <20mg/dl and specific gravity 相似文献   

Effect of murine retroviral infection on hair and serum levels of cocaine and morphine.

LP-BM5 retrovirally infected female C57BL/6J mice were administered cocaine, morphine or both by daily intraperitoneal injection for 9 weeks. Drug concentrations were measured by radioimmunoassay in serum and in hair extracts. Hair samples obtained from all drug-treated mice were positive for the drug injected, while none of the saline-treated mice had detectable drug levels in hair or serum. The average morphine concentration obtained from non-infected mice was 11 ng/mg hair whereas the amount found in the LP-BM5-infected mice was significantly higher (20 ng/mg hair). Mice injected with both morphine and cocaine were given 50% of the regular dose of each drug and drug levels in the hair of these animals were approximately half that of mice injected with the full dose of the single drug. Non-infected mice treated with both drugs had a mean value of 7 ng morphine/mg hair and 374 ng cocaine/mg hair while retrovirus-infected mice had significantly higher concentrations, 10 ng morphine/mg hair and 1160 ng cocaine/mg hair (P less than 0.001). Serum concentrations of cocaine and morphine were significantly higher (P less than 0.01) in the retrovirus-infected animals from 40 min to 1.5 h. The increased concentrations of cocaine and morphine in serum during retrovirus infection are accompanied by a significant increase in the amount of drug incorporated into the hair matrix. This change indicates that retroviral infection may influence the disposition of these drugs in the systemic circulation.     

Concurrent detection of heroin, fentanyl, and xylazine in seven drug-related deaths reported from the Philadelphia Medical Examiner's Office

Recreational drugs, such as cocaine and heroin, are often adulterated with other pharmacological agents to either enhance or diminish the drug effects. Between April 21, 2006 and August 8, 2006, the Philadelphia Medical Examiner's Office detected xylazine (a veterinary sedative) and fentanyl (a synthetic opioid) in specimens taken from seven cases. Initial immunoassay screening was performed on urine and blood for fentanyl, opiate, cocaine, phencyclidine (PCP), and benzodiazepines. All tests reported positive were confirmed by gas chromatography-mass spectrometry. All seven xylazine positive cases tested positive for fentanyl and six cases tested positive for 6-acetylmorphine (a metabolite and definitive marker for heroin). The seventh case was positive for morphine and had a history of heroin abuse. Xylazine was present in urine in all seven cases and blood levels were detected in three cases. The blood concentrations ranged from trace to 130 ng/mL. Fentanyl was present in the blood and urine in each case and blood concentrations ranged from 4.7 to 47 ng/mL. Adulteration of illicit drugs has become an epidemic health concern for drug users. Healthcare professionals need to be aware of this issue, so the patients can be treated in an effective, timely manner.     

氯胺酮滥用的毛发分析研究

目的建立毛发中氯胺酮及其代谢物的分析方法并探索氯胺酮进入毛发的机理。方法通过建立豚鼠连续给药(不同剂量)实验模型获取阳性头发和采集氯胺酮滥用者头发,经处理后用GC/MSscan和SIM法分析,以鉴别、确认毛发中氯胺酮及其代谢物。结果豚鼠毛发中氯胺酮的质量分数与给药剂量存在明显的正相关性。毛发中氯胺酮质量分数依白色、棕色、黑色毛发顺序随毛发中黑色素的质量分数增加而增加。豚鼠毛发中氯胺酮与代谢物NK质量分数之比为2.33～12.94,仅在高剂量组的豚鼠毛发中才检测到DHNK,其质量分数与NK接近。15名氯胺酮滥用者黑色头发中均检出原体和代谢物NK,但DHNK少见。豚鼠毛发中代谢物相对质量分数明显高于人。结论本实验结果很好地反映了药物进入毛发代谢过程与药物和黑色素亲和力以及药物的亲脂性密切相关这一规律,但人和动物在药物代谢及进入毛发的难易程度上存在差异。本方法可以用于法庭毒物分析领域头发中氯胺酮的检测。     

单次摄药毛发分析的研究进展

“迷药犯罪”是指对被害人下药后实施性侵犯、抢劫、诈骗等犯罪行为。单次摄入的镇静催眠类或迷幻类药物在体内迅速代谢,故难以用血液、尿液检测等常规方法来提供摄药证据,而毛发分析的长检测窗特点在解决这类案件时具有重要的价值。单次摄药的毛发分析要求检测方法有很高的灵敏度,需要用二级质谱检测器进行分析,且从头发采样、去污、水解、提取、分析的各环节均应注意防止污染,避免出现假阳性结果。采集的头发必须进行分段分析,除检测对应案发时间的头发段外,还应把其它头发段的检测结果作为对照,据此对分析结果作出严谨、科学的解释。目前已建立了31种镇静催眠药、6种苯丙胺类衍生物、GHB、硫喷妥及其代谢物戊巴比妥以及乙醇代谢物EtG等的检测方法,可以应用于实际案件的毛发分析。     

Detection of drugs of abuse in simultaneously collected oral fluid, urine and blood from Norwegian drug drivers

Blood and urine samples are collected when the Norwegian police apprehend a person suspected of driving under the influence of drugs other than alcohol. Impairment is judged from the findings in blood. In our routine samples, urine is analysed if morphine is detected in blood to differentiate between ingestion of heroin, morphine or codeine and also in cases where the amount of blood is too low to perform both screening and quantification analysis. In several cases, the collection of urine might be time consuming and challenging. The aim of this study was to investigate if drugs detected in blood were found in oral fluid and if interpretation of opiate findings in oral fluid is as conclusive as in urine. Blood, urine and oral fluid samples were collected from 100 drivers suspected of drugged driving. Oral fluid and blood were screened using LC-MS/MS methods and urine by immunological methods. Positive findings in blood and urine were confirmed with chromatographic methods. The analytical method for oral fluid included 25 of the most commonly abused drugs in Norway and some metabolites. The analysis showed a good correlation between the findings in urine and oral fluid for amphetamines, cocaine/benzoylecgonine, methadone, opiates, zopiclone and benzodiazepines including the 7-amino-benzodiazepines. Cocaine and the heroin marker 6-monoacetylmorphine (6-MAM) were more frequently detected in oral fluid than in urine. Drug concentrations above the cut-off values were found in both samples of oral fluid and urine in 15 of 22 cases positive for morphine, in 18 of 20 cases positive for codeine and in 19 of 26 cases positive for 6-MAM. The use of cannabis was confirmed by detecting THC in oral fluid and THC-COOH in urine. In 34 of 46 cases the use of cannabis was confirmed both in oral fluid and urine. The use of cannabis was confirmed by a positive finding in only urine in 11 cases and in only oral fluid in one case. All the drug groups detected in blood were also found in oral fluid. Since all relevant drugs detected in blood were possible to find in oral fluid and the interpretation of the opiate findings in oral fluid was more conclusive than in urine, oral fluid might replace urine in driving under the influence cases. The fast and easy sampling is time saving and less intrusive for the drivers.     

Postmortem toxicology of drugs of abuse

Conducting toxicology on post-mortem specimens provides a number of very significant challenges to the scientist. The range of additional specimens include tissues such as decomposing blood and other tissues, hair, muscle, fat, lung, and even larvae feeding on the host require special techniques to isolate a foreign substance and allow detection without interference from the matrix. A number of drugs of abuse are unstable in the post-mortem environment that requires careful consideration when trying to interpret their significance. Heroin, morphine glucuronides, cocaine and the benzodiazepines are particularly prone to degradation. Moreover, redistributive process can significantly alter the concentration of drugs, particularly those with a higher tissue concentration than the surrounding blood. The designer amphetamines, methadone and other potent opioids will increase their concentration in blood post-mortem. These processes together with the development of tolerance means that no concentration of a drug of abuse can be interpreted in isolation without a thorough examination of the relevant circumstances and after the conduct of a post-mortem to eliminate or corroborate relevant factors that could impact on the drug concentration and the possible effect of a substance on the body. This article reviews particular toxicological issues associated with the more common drugs of abuse such as the amphetamines, cannabinoids, cocaine, opioids and the benzodiazepines.     

The incorporation of dyes into hair as a model for drug binding

The binding of charged substances from external aqueous media to hair has been investigated through the use of fluorescence microscopy. Eleven hair samples, reflecting various ethnic groups and cosmetic treatments, were tested. Rhodamine 6G, a cationic dye representative of drugs such as cocaine and opiates, showed incorporation throughout the hair of all samples except one. In contrast, fluorescein, an anionic dye representative of drugs such as THC carboxylic acid, was not readily incorporated. The incorporation of rhodamine 6G was faster for chemically 'straightened' and bleached African-American female hair than for untreated hair. Incorporation of rhodamine 6G followed a pH dependence, but an ionic strength dependence could not be established. These studies support three postulates: (1) electrostatic interactions explain the preferential binding of cationic drugs of abuse to hair; (2) the hair matrix, or the non-helical portion of hair, is accessible to external solutions and thus subject to contamination; and (3) cosmetic treatments may alter the helical portion of hair thereby increasing its accessibility to external contamination.