Journal of Analytical Toxicology 2015;39:624 –628
doi:10.1093/jat/bkv067
Special Issue
Detection of Drugs in Nails: Three Year Experience
Irene Shu, Joseph Jones, Mary Jones, Douglas Lewis and Adam Negrusz*
United States Drug Testing Laboratories, Inc., 1700 South Mount Prospect Road, Des Plaines, IL 60017, USA
*Author to whom correspondence should be addressed. Email: [email protected]
Nails (fingernails and toenails) are made of keratin. As the nail grows,
substances incorporate into the keratin fibers where they can be
detected 3 – 6 months after use. Samples are collected by clipping
of 2 –3 mm of nail from all fingers (100 mg). We present drug testing
results from 10,349 nail samples collected from high-risk cases during a 3-year period of time. Samples were analyzed by validated analytical methods. The initial testing was performed mostly using
enzyme-linked immunosorbent assay, but by liquid chromatography–tandem mass spectrometry (LC –MS-MS) as well. Presumptive
positive samples were subjected to confirmatory testing with sample
preparation procedures including washing, pulverizing, digestion and
extraction optimized for each drug class. The total of 7,799 samples
was analyzed for amphetamines. The concentrations ranged from 40
to 572,865 pg/mg (median, 100 –3,687) for all amphetamine analytes.
Amphetamine and methamphetamine were present in 14% of the
samples, 22 samples were positive for 3,4-methylenedioxymethamphetamine (0.3%), 7 for methylenedioxyamphetamine (0.09%) and 4
for 3,4-methylenedioxy-N-ethylamphetamine (0.05%). Cocaine and
related analytes were found in 5% samples (7,787 total), and the
concentration range was 20 – 265,063 pg/mg (median 84 – 1,768).
Opioids overall ranged from 40 to 118,229 pg/mg (median 123 –
830). The most prevalent opioid was oxycodone (15.1%) and
hydrocodone (11.4%) compared with 1.0–3.6% for the others, including morphine, codeine, hydromorphone, methadone, 2-ethylidene1,5-dimethyl-3,3-diphenylpyrrolidine and oxymorphone. Carboxy-D-9tetrahydrocannabinol positivity rate was 18.1% (0.04 – 262 pg/mg,
median 6.41). Out of 3,039 samples, 756 were positive (24.9%) for
ethyl glucuronide (20 – 3,754 pg/mg, median 88). Other drugs found
in nails included barbiturates, benzodiazepines, ketamine, meperidine,
tramadol, zolpidem, propoxyphene, naltrexone and buprenorphine.
Nail analyses have become a reliable way of determining the longterm use and abuse of drugs. Extraction techniques are simple and produce accurate and precise results. Sensitive analytical instrumentation,
mainly LC–MS-MS, allows for detection of femtogram (10215 g) quantities of substances in nails. Samples were from a high-risk population,
therefore the extraordinary positivity rate was observed.
Introduction
During the last several decades, nails (fingernails and toenails)
have become a useful specimen type for detection of drug use
and abuse, as well as the exposure to other substances such as
heavy metals (1 – 3). Nails are made of keratin. The average
growth rate for fingernails is 3 mm per month (range between
1.9 and 4.4 mm/month) (3). Toenails grow 30 – 50% slower
than fingernails and are much more susceptible to drug contamination from sweat (1, 3). As the nail grows, chemicals (illicit substances, drugs, alcohol biomarkers, etc.) incorporate into the
keratin fibers where they can stay for extended periods of time
(3 – 5 months in fingernails, and 8 – 14 months in toenails) (3).
The mechanisms of drug deposition in nails have not been
extensively studied. In two recently published reports, the
mechanisms of incorporation of zolpidem (ZOL) after a single
oral dose were investigated (4, 5). The results revealed potentially three mechanisms of drug incorporation to nails: (i) contamination from sweat detectable 24 h after drug intake, (ii)
incorporation from nail bed (vertical growth) detected after
2 weeks and (iii) incorporation from germinal matrix (horizontal
growth), where concentration is peaking on average 3 months
after drug administration. The authors showed ZOL incorporation from sweat being irremovable by daily hygiene (5). The concentration of ZOL was higher in toenails than in fingernails (4).
An extensive review of application of nail testing in drug treatment programs, identification of in utero exposure to drugs,
therapeutic drug monitoring, forensic toxicology including
postmortem applications and drug facilitated sexual assault was
recently published by Cappelle et al. (1).
Both hair and nails are keratinized specimens. There are a few
differences between nails and hair impacting the usefulness in
drug testing. First, both fingernails and toenails grow continuously and do not have the growth cycle characteristic for hair (1, 3).
In addition, nails do not contain melanin and for that reason are
free of hair-color bias. Physicochemical properties of drugs play
an important role in deposition in nails. Specifically, substances
not containing a nitrogen atom may accumulate in nails at higher
concentrations than in hair (1). For example, the concentrations
of ethyl glucuronide (EtG) and 11-nor-D9-THC-9-carboxylic acid
(THCA) in nails are 3 times and 4.9 times, respectively, higher
than in the corresponding hair samples (6, 7).
In this article, we present the survey of drug testing results in
10,349 nail samples collected from high-risk populations for
prevalence and concentrations during a 3-year period of time
between 2012 and 2014. In addition, we show the differences
in concentrations of drugs in fingernails and toenails. All samples
were analyzed by validated analytical procedures. The initial testing was performed using either enzyme-linked immunosorbent
assay (ELISA), or by liquid chromatography–tandem mass spectrometry (LC–MS-MS). Presumptive positive samples were then
subjected to confirmatory testing with sample preparation procedures including washing, pulverizing, digestion and extraction optimized for each drug class.
Experimental
Specimens and analytes
Approximately 3 mm clippings (100 mg) from all nails were
submitted to the laboratory for analysis for drugs specified by
the requestors on the chain of custody forms. The samples
came from drug courts, child advocacy centers, drug treatment
facilities, drunk driving programs, reference laboratories, physicians/health professionals’ programs, lawyers, etc.
All samples were screened for the requested drug classes, and
the presumptive positive results were subjected to confirmatory
# The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: [email protected]
testing for the following targeted analytes: amphetamine (AMP),
methamphetamine (MET), 3,4-methylenedioxymethamphetamine (MDMA), methylenedioxyamphetamine (MDA), 3,4-methylenedioxy-N-ethylamphetamine (MDEA), cocaine (COC),
benzoylecgonine (BE), norcocaine (NCOC), cocaethylene (CE),
6-monoacetylmorphine (6-MAM), codeine (COD), morphine
(MOR), hydromorphone (HYM), hydrocodone (HCOD), oxycodone (OXC), oxymorphone (OXM), methadone (MTD),
2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), fentanyl (FE), norfentanyl (NFE), sufentanil (SUF), norsufentanil
(NSUF), propoxyphene (PPX), norpropoxyphene (NPPX), buprenorphine (BUP), norbuprenorphine (NBUP), meperidine (MEP),
normeperidine (NMEP), tramadol (TRAM), naltrexone (NALT),
naloxone (NAL), 6-beta-naltrexol (6-BNAL), nalbuphine (NALB),
butorphanol (BTF), THCA, phencyclidine (PCP), butalbital
(BUT), amobarbital (AMO), pentobarbital (PEN), secobarbital
(SEC), phenobarbital (PHB), midazolam (MDZ), oxazepam (OX),
alprazolam (ALP), temazepam (TEM), diazepam (DIAZ), nordiazepam (NDIAZ), propofol glucuronide (PPFG), ketamine (KET), norketamine (NKET), ZOL and EtG.
Sample preparation
Nail samples were washed with acetone once for the ELISA initial
testing and the majority of the confirmatory methods. Some exceptions included THCA, BUP and NBUP, where methylene chloride wash was employed. If EtG or PPFG analysis was requested,
the specimens were washed with hexane followed by 10-min
sonication in methylene chloride, and finally washed with methanol. All initial washes were discarded.
Immediately after the wash, nail samples were dried at room
temperature and pulverized using mini ball beater with 3 mm
diameter stainless-steel balls. Calibrations were performed by fortifying pulverized drug-free nail aliquots with standard working
solutions of all analytes of interest. In addition, three levels of
controls were prepared in naı̈ve pulverized nails fortified
with corresponding working control solutions of all analytes.
Depending on the analyte, various nail digestion or incubation
methods optimized for each drug class were employed. Acid
digestion (0.1 N hydrochloric acid at 538C overnight) was used
for amphetamines, COC and metabolites, selected opioids also
including NALT, NAL, 6-BNAL, NALB, BTF, and PCP, MTD,
EDDP, PPX, NPPX, TRAM, NMEP, NFE, NSUF, KET and NKET.
The two-step process was used for 6-MAM to be co-analyzed
with the opioids including COD, MOR, HYM, HCOD, OXC and
OXM. First, the powdered nail sample was sonicated with methanol for 3 h. After centrifugation, the methanol supernatant was
decanted to a separate tube and the remaining nail powder was
digested in 0.1 N hydrochloric acid at 538C overnight. Basic
digestion with 1 N sodium hydroxide at 808C for 1 h was applied
for THCA. Sonication for 2 h in deionized water without heat
with subsequent overnight incubation at room temperature
was utilized for EtG and PPFG analysis. After digestion or incubation, the nail extracts were subjected to the corresponding solidphase extraction (SPE) methods. The methanol incubation was
used for the rest of the drugs: barbiturates (538C overnight), benzodiazepines (2-h sonication with heat followed by incubation at
room temperature overnight) and ZOL (sonication for 4 h with
heat). The methanol extracts were then evaporated and reconstituted with the corresponding LC mobile phases for analysis.
Preliminary testing and confirmation
After initial preparation, the samples underwent preliminary testing by ELISA, except for BUP, EtG, KET, NKET, NALT, NAL, 6-BNAL,
NALB, BTF and PPFG for which the instrumental screening by LC–
MS-MS was employed. LC–MS-MS was also used for confirmatory
analysis for the majority of drug classes except for PCP, barbiturates, TRAM and NMEP. For the latter, gas chromatography–mass
spectrometry (GC–MS) was employed. The presence of THCA in
nails was confirmed by GC–GC–MS-MS. The examples of the entire analytical approach to analysis of nail samples in our laboratory
were discussed by Jones et al. (6, 7).
Results and discussion
In this study, we report the results of analysis of 10,349 nail samples acquired between 1 January 2012 and 31 December 2014.
All specimens were collected from elevated risk groups such as
drug treatment programs, physicians/health professionals’ programs, drug courts, and child advocacy centers with the expected high rate of positivity. The results are presented in Table I.
The comparison of fingernail and toenail results is presented in
Table I.
Summary of Nail Results in Three Years (2012– 2014)
Analyte
LOQ
(pg/mg)
Number of
samples LOQ/
total samples
tested
% of
samples
LOQ
14.4
13.7
Minimum –
maximum range
(pg/mg)
AMP
MET
40
40
1,126/7,799
1,071/7,799
MDMA
MDA
MDEA
COC
40
40
40
40
22/7,799
7/7,799
4/7,799
415/7,787
BE
NCOC
CE
6-MAM
COD
MOR
HYM
HCOD
OXC
OXM
MTD
20
20
20
40
40
40
40
40
40
40
40
406/7,787
199/7,787
93/7,787
115/7,779
144/7,779
283/7,779
170/7,779
885/7,779
485/3,202
83/3,202
44/3,567
5.2
2.6
1.2
1.5
1.9
3.6
2.2
11.4
15.1
2.6
1.2
35/3,567
1/3,567
15/40
12/40
1/1,344
53/1,344
1.0
0.03
37.5
30.0
0.07
3.9
49 –2,880
45
37 –5,491
9 –216
1,481
425 –158,072
EDDP
NPPX
BUP
NBUP
NMEP
TRAM
40
40
8
8
1,000
400
0.3
0.09
0.05
5.3
40 –44,851
42 –572,865
43 –40,165
52 –706
50 –422
48 –265,063
23 –141,239
20 –3,875
20 –934
45 –118,229
41 –32,358
40 –105,932
41 –62,857
40 –116,341
41 –36,987
42 –47,724
94 –17,859
NALT
6-BNAL
THCA
PCP
BUT
40
40
0.02
40
200
2/18
9/18
1,412/7,797
3/7,774
22/4,079
11.1
50.0
18.1
0.04
0.5
63 –71
115 –2,261
0.04 –262
72 –13,488
486 –19,101
PHB
ALP
TEM
DIAZ
NDIAZ
KET
NKET
ZOL
EtG
200
40
40
40
40
40
40
4
8
2/4,079
64/4,083
3/4,083
37/4,083
35/4,083
2/122
1/122
1/4
756/3,039
0.05
1.6
0.07
0.9
0.9
1.6
0.8
25.0
24.9
3,659 –4,653
45 –1,553
47 –3,769
41 –5,338
46 –1,604
3,772 –12,632
201
344
20 –3,754
Median/
mean
(pg/mg)
831/2,005
3,687/
13,197
298/2,773
129/250
100/168
1,768/
13,600
971/4,520
105/305
84/145
830/8,774
163/739
445/3,975
123/986
633/1,351
614/2,082
155/1,469
2,237/
3,245
527/696
na
182/782
43/65
na
3,553/
8,606
na
484/749
6.41/13.73
630/4,730
1,811/
3,214
na
152/251
99/1,305
233/560
139/260
na
na
na
88/177
Detection of Drugs in Fingernails and Toenails 625
Table II. The sample numbers as well as the concentration ranges
in Table II may differ from what is presented in Table I. The
reason is that our laboratory started systematically recording
the type of nail (finger- vs. toenail) in May of 2014. Table II
includes only results where the type of specimen was clearly
indicated.
The total of 7,799 samples was analyzed for amphetamines
(AMP, MET, MDMA, MDA and MDEA). AMP and MET were present in 14.4 and 13.7%, respectively, of the nail samples, and
the concentration ranges were 40 – 44,851 pg/mg (median
831) and 42 – 572,865 pg/mg (median 3,687), respectively. As
in our study, higher concentrations of MET than AMP in nails
were observed by Suzuki et al. (8) with the highest MET concentration of 642 ng/mg. The authors employed incubation of specimens in 0.6 M hydrochloric acid followed by liquid – liquid
extraction (chloroform – isopropanol, 3:1, v/v). The samples we
collected did not show obvious concentration difference between fingernails and toenails for AMP and MET (Table II).
However, previous studies showed higher concentrations of
the compounds in toenails than in fingernails from limited number of tested subjects (1). There were only 22 samples found positive for MDMA (0.3%), 7 for MDA (0.09%) and 4 for MDEA
(0.05%), and the concentration ranges were 43 – 40,165 pg/mg
(median 298), 52 – 706 pg/mg (median 129) and 50 – 422 pg/
mg (median 100), respectively. There was limited information
in our study to compare MDA, MDMA and MDEA concentrations
between fingernails and toenails. Cirimele et al. (9) reported
MDA and MDMA concentrations in fingernails of 9.7 and
60.2 ng/mg, respectively, which for MDA is significantly higher
than that in our study. MDMA results corroborate with our findings. The authors also noticed that the concentrations of AMP,
MDA and MDMA in fingernails were slightly higher than in
head hair (9). In the study by Kim et al. (10), MDA concentration
in one positive sample was ,143 pg/mg. The study also found
KET in fingernail clippings at the concentration of 0.314 ng/mg
(below the limit of quantitation). In our study, KET was found in
two nail samples at concentrations of 3,772 and 12,632 pg/mg.
NKET was found in one sample only and the concentration was
201 pg/mg.
COC, BE, NCOC and CE were found in 5.3, 5.2, 2.6, and 1.2% of
nail samples, respectively, out of 7,787 total specimens where
these analytes were requested. COC concentrations ranged from
48 to 265,063 pg/mg (median 1,768), BE from 23 to141,239 pg/
mg (median 971), NCOC between 20 and 3,875 pg/mg (median
105) and the range for CE was 20–934 pg/mg (median 84). The
data show that COC was present in both fingernails and toenails in
higher concentrations than BE (Table I). As presented in Table II,
higher concentrations of COC and BE were observed in fingernails
than in toenails. Engelhart et al. (11) found higher concentrations
of BE than COC in postmortem toenails from subjects of unspecified drug use history. The highest concentrations of COC and BE
were 140.17 ng/g and 315.44 ng/mg, respectively. The highest
concentration of NCOC was 6.78 ng/mg, and CE 2.6 ng/mg (11).
Garside et al. (12) reported COC and BE to be predominant
analytes in all postmortem positive nail specimens from suspected
cocaine users. The application of SPE and solvent extraction
followed by GC–MS quantification revealed the ratio of COC to
BE to be 2 – 10:1. The analysis of nails in postmortem cases by
Engelhart and Jenkins (13) showed maximum COC concentrations
to be much higher than BE (414.1 and 170.3 ng/mg, respectively).
In addition, concentrations of all COC analytes were higher in fingernails than in toenails. The NCOC concentration range was
0.11–32.7 ng/mg, much higher than in Garside’s study (12) and
in this report (20–3,875 pg/mg). CE levels were similar to reported by Garside et al. (12) and here.
Concentrations of selected opioids (MOR, COD, 6-MAM, HCOD
and HYM) in nail samples are presented in Table I. The levels overall ranged from 40 to 118,229 pg/mg (median 123 – 830). The
most prevalent of the above five opioids was HCOD. It was detected in 11.4% of 7,779 tested nail samples, compared with 1.5–3.6%
Table II.
Comparison of Fingernail and Toenail Results (2014)
Analyte
Number of samples LOQ/total samples tested
(% of samples LOQ)
Minimum –maximum range (pg/mg)
Median/mean (pg/mg)
Fingernails
Fingernails
Toenails
Fingernails
Toenails
AMP
MET
MDMA
COC
BE
NCOC
CE
6-MAM
COD
MOR
HYM
HCOD
OXC
OXM
MTD
EDDP
BUP
NBUP
THCA
ALP
DIAZ
NDIAZ
EtG
212/1,542
190/1,542
4/1,542
84/1,540
82/1,540
38/1,540
21/1,540
30/1,540
31/1,540
57/1,540
41/1,540
134/1,540
107/606
25/606
7/703
7/703
5/14
4/14
255/1,539
22/835
8/835
9/835
157/650
42– 29,105
80– 249,706
70– 3,834
159 – 265,063
41– 45,939
20– 2,357
22– 463
51– 118,229
41– 6,882
47– 66,666
41– 62,857
59– 13,473
43– 18,482
42– 24,902
1,534 – 4,640
139 – 1,277
52– 5,491
9 – 54
0.12– 146
57– 1,117
43– 461
55– 638
20– 3,121
40– 44,851
47– 344,619
99
306 – 6,067
166 – 6,887
68– 144
221 – 252
122 – 22,935
45– 805
40– 11,857
53– 1,188
113 – 8,611
50– 3,827
42– 280
11,896
1,721
37– 175
35– 62
0.15– 106
61– 148
43– 247
389 – 438
23– 254
980/1,879
3,784/16,148
2,564/2,258
2,101/18,510
1,285/4,803
120/289
61/90
2,959/18,645
192/816
780/7,209
127/1,813
913/1,663
737/2,148
124/1,278
3,401/3,141
370/582
299/1,271
23/28
6.4/13.2
207/315
190/216
93/179
82/186
843/2,906
3,021/15,717
na/na
1,281/2,143
594/1,293
71/94
na/na
1,051/4,681
130/201
285/1,466
115/283
753/1,363
385/879
108/119
na/na
na/na
na/na
na/na
8.4/15
na/na
na/na
na/na
59/75
626 Shu et al.
Toenails
(13.7%)
(12.3%)
(0.3%)
(5.5%)
(5.3%)
(2.5%)
(1.4%)
(1.9%)
(2.0%)
(3.7%)
(2.7%)
(8.7%)
(17.7%)
(4.1%)
(1.0%)
(1.0%)
(35.7%)
(28.6%)
(16.6%)
(2.6%)
(1.0%)
(1.1%)
(24.2%)
99/550
73/550
1/550
16/550
16/550
3/550
2/550
6/550
11/550
15/550
12/550
44/550
29/214
5/214
1/251
1/251
2/6
2/6
110/551
2/304
2/304
2/304
16/66
(18.0%)
(13.3%)
(0.2%)
(2.9%)
(2.9%)
(0.5%)
(0.4%)
(1.1%)
(2.0%)
(2.7%)
(2.2%)
(8.0%)
(13.6%)
(2.3%)
(0.4%)
(0.4%)
(33.3%)
(33.3%)
(20.0%)
(0.7%)
(0.7%)
(0.7%)
(24.2%)
for the other four. 6-MAM, heroin metabolite, was present in 115
samples out of 7,779 and the concentration range was 45 –
118,229 pg/mg. Concentrations of all opioids were much higher
in fingernails than in toenails (Table II). Engelhart et al. (11)
found MOR, 6-MAM and HCOD in postmortem toenails from subjects of unspecified drug use history at average concentrations
0.37, 0.89 and 0.62 ng/mg, respectively, and they were significantly lower than in our report (Table II). In another study, the
same author (13) reported the presence of MOR, 6-MAM, COD,
HYM, OXC and HCOD in postmortem nail clippings from subjects
with documented drug abuse history and/or drug-related homicide. Concentrations of MOR and 6-MAM were this time significantly higher than in our report (0.05–407.9 and 0.04–504 ng/
mg, respectively). COD concentrations in postmortem nails corresponded well to concentrations observed by us. Other opioids
including MTD, EDDP, OXC and OXM were found in 1.2, 1.0,
15.1, and 2.6%, respectively, of approximately 3,400 samples analyzed. MTD and its metabolite EDDP were found in 44 and 35 samples, respectively, out of 3,567 submitted for analysis for these
analytes. The concentrations ranged from 94 to 17,859 pg/mg
for MTD, and from 49 to 2,880 pg/mg for EDDP. Lemos et al.
(14) found MTD in fingernail clippings collected from patients
in a methadone-maintenance program. The mean MTD concentration was 26.9 ng/mg and was significantly higher than the mean
concentration in this report (3,245 pg/mg).
Very limited information is available on the presence of other
opioids (and opioid antagonists) such as BUP, NBUP, NALT, NAL,
6-BNAL, NALB or BTF in nails. BUP and NBUP were found in 15
and 12 nail samples, respectively, out of 40 submitted for analysis.
The concentration range for BUP was 37 – 5,491 pg/mg (mean
782 pg/mg) and 9 – 216 pg/mg (mean 65 pg/mg) for NBUP.
Very recently, Tzatzarakis et al. (15) reported the presence of
BUP, NBUP and NAL in fingernails and urine collected from heroin users undergoing suboxone substitution therapy. The mean
nail concentrations were as follows: BUP 163 pg/mg, NBUP
129 pg/mg and NAL 47.4 pg/mg. We did not receive nail samples
with concomitant request for testing for both BUP/NBUP and
NAL. Also, NAL was not detected in any nail sample. On the
other hand, NALT was found in only two nail samples (63 and
71 pg/mg), and 6-BNAL, NALT metabolite, was present in 9 out
of 18 samples received, in concentrations ranging from 115 to
2,261 pg/mg. To date, there were no prior studies reporting
NALT (used in alcohol dependence treatment) and its metabolite
tested in nails.
The detection of THCA is very important to differentiate between marijuana ingestion (intentional and/or passive inhalation)
and external contamination (1). In our study, concentrations of
THCA in nails ranged from 0.04 to 262 pg/mg (median 6.41),
and the overall positivity rate was 18.1%. The mean concentration
in fingernails was 13.2 pg/mg, and in toenails 15 pg/mg. The concentration ranges were also very similar suggesting that both specimens are equally useful in revealing cannabis use. Jones et al. (6)
developed a highly sensitive GC – GC – MS-MS method with the
limit of detection and quantification of 10 and 20 fg/mg, respectively, for quantification of THCA in 60 matched hair and nail specimens. The mean THCA concentration in nails was 1,813 fg/mg,
lower than the mean concentration in this study (13.7 pg/mg).
Out of 3,039 samples submitted for analysis for EtG, 756 were
positive (24.9%), and a concentration range was 20–3,754 pg/mg
(median 88, mean 177). In another study by Jones et al. (7), the
reported EtG mean concentration was 29.1 pg/mg, and it was
three times higher than in the corresponding hair samples of
college students (age 18–26 years). The mean concentration was
significantly lower than in this report where subjects expressed
risky alcohol drinking behavior. Morini et al. (16) found a
correlation between EtG concentration in fingernails and
self-reported alcohol consumption. The highest EtG concentration
was 92.6 pg/mg for a person consuming .60 g of alcohol per day.
Berger et al. (17) also found that EtG in fingernails at 30 pg/mg has
100% sensitivity to identify high-risk drinking behavior (30 standard drinks per week), and 100% specificity to rule out abstinence
compared with hair EtG at 30 pg/mg. The highest EtG concentration in fingernails was 397.08 pg/mg. Both studies concluded that
the detection of EtG in nails is a better alcohol use biomarker than
in hair.
Examples of other drugs found in nails include barbiturates,
benzodiazepines, NMEP, PCP, TRAM and NPPX. The positivity
rate for benzodiazepines in nails was below 1% except for ALP
(1.6%) (Tables I and II).
In summary, as this report indicates, nails are a very useful matrix for detection of drugs and illicit substances, and for analytes
such as THCA or EtG, may be a superior alternative specimen
type to hair samples. Nail sample preparation is relatively simple
and the advancement in analytical equipment technology allows
for accurate measurements of extremely low quantities of parent
compounds as well as the metabolites. Most drugs are present at
greater concentration than their metabolites. NALT is an exceptional case where its metabolite 6-BNAL, not a parent drug, is the
predominant form present in nails. It is worth pointing out that
the concentrations of substances found antemortem in our study
are largely comparable with concentrations reported in postmortem cases, whether or not the causes or manners of death were
drug-related. More research is necessary to better understand
and interpret the analytical findings.
Conclusion
Analysis of nails is a reliable way of determining the long-term use
and abuse of drugs. Extraction techniques are simple and produce accurate and precise results. Sensitive analytical instrumentation allows for detection of femtogram quantities of substances
in nails. Prescription drugs, drugs of abuse and illicit substances
can be detected and quantified in both fingernails and toenails in
a wide range of concentrations. Except for AMP, the mean concentrations of drugs in fingernails are higher than in toenails.
With very few exceptions, parent compounds typically reach
higher concentrations in nails than their metabolites. More research studies are necessary to better understand the significance and the meaning of nail results.
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