Prolonged detection of urine norfentanyl in individuals enrolled in a medication for opioid use disorder in pregnancy and postpartum program: a case series

BACKGROUND

Although urine drug testing can have vast legal and social ramifications, its interpretation during pregnancy and after birth remains not well understood. Fentanyl metabolism is altered by an individual's genetics, history of opioid use, and liver function. However, little is known about the clearance of fentanyl or its primary metabolite, norfentanyl, in the peripartum period.

OBJECTIVE

We sought to identify and describe cases of delayed urine norfentanyl clearance in the pregnancy and postpartum period within our institution.

STUDY DESIGN

This study described 3 cases of delayed urine norfentanyl clearance in pregnant and postpartum individuals in a colocated obstetrics, postpartum, and addiction medicine program. This program included prescriptions for medication for opioid use disorder and weekly urine drug testing with fentanyl immunoassay with reflex confirmation testing with liquid chromatography-tandem mass spectrometry for positive results with a limit of detection of 2.5 ng/mL.

RESULTS

Low levels of norfentanyl (<16.3 ng/mL) were detected in urine 294 days, 126 days, and 231 days after the last fentanyl use. Patient self-reported abstinence was supported by consistently negative urine fentanyl levels throughout the collection period, compliant weekly urine drug tests that were otherwise only positive for buprenorphine, and negative fentanyl and norfentanyl in umbilical cord toxicology.

CONCLUSION

Despite compliance in a medication for opioid use disorder program, the presence of norfentanyl in urine has significant consequences on the maternal-child dyad in the postpartum period. Caution should be used when using low levels of norfentanyl to determine an individual's abstinence, as it can lead to further discrimination against women in medication for opioid use disorder programs.

An Ultrasensitive Norfentanyl Sensor Based on a Carbon Nanotube-Based Field-Effect Transistor for the Detection of Fentanyl Exposure

The opioid crisis is a worldwide public health crisis that has affected millions of people. In recent years, synthetic opioids, primarily illicit fentanyl, have become the primary driver of overdose deaths. There is a great need for a highly sensitive, portable, and inexpensive analytical tool that can quickly indicate the presence and relative threat of fentanyl. In this work, we develop a semiconductor enriched (sc-) single-walled carbon nanotube (SWCNT)-based field-effect transistor (FET) biosensor functionalized with norfentanyl antibodies for the sensitive detection of norfentanyl, the primary inactive metabolite of fentanyl, in urine samples. Different sensor configurations were explored in order to obtain the most optimized sensing results. Moreover, by employing the "reduced" antibody, we achieved orientated immobilization of the norfentanyl antibody and thus brought the antigen-antibody interaction closer to the sensor surface, further improving the sensitivity. The reported norfentanyl biosensors have a limit of detection in the fg/mL region in both calibration samples and synthetic urine samples, showing ultrasensitivity and high reliability.

Determination of fentanyl and norfentanyl in cerumen in the setting of postmortem investigation

Cerumen is an emerging alternative biological matrix in the field of forensic toxicology. An ultra-high-pressure liquid chromatography-mass spectrometry/mass spectrometry [UHPLC-MS/MS] method for the determination of fentanyl and norfentanyl in cerumen was developed and applied in a mixed drug toxicity fatal case. The method was found to be selective and sensitive (LOQ: 0.05 ng/mg for fentanyl and 0.02 ng/mg for norfentanyl), while validation included recovery, carryover, short-term stability, matrix effect, accuracy, and precision (RSD%). Accuracy ranged from 83.1% to 103.5%, while intra- and inter-day precision ranged from 8.6% to 13.1% and from 8.3% to 15.8%, respectively. Matrix effect experiments showed that matrix did not significantly affect signal intensity (82.3%-96.8%). Short-term stability concerning sample extracts was found satisfactory. Fentanyl and norfentanyl were detected in cerumen at a concentration of 1.17 and 0.36 ng/mg respectively. The findings in cerumen corroborate the cause of death and suggest that cerumen is a potential specimen for detecting drugs of abuse in forensic cases.

Comparison of Oral Fluid and Urine for Detection of Fentanyl Use Using Liquid Chromatography with Tandem Mass Spectrometry

BACKGROUND

We compared oral fluid (OF) and urine (UR) for detection of fentanyl (FEN) use in addiction medicine-psychiatry (AMP) clinics.

METHODS

We measured FEN and norfentanyl (NRFEN) in UR with a limit of detection (LOD) of 2.0 µg/L and FEN in OF with an LOD of 0.5 µg/L by LC-MS/MS in 311 paired samples and compared the 2 matrices when higher OF and UR LODs were used.

RESULTS

Urine (UR) detected more FEN use than OF using a LOD of 2.0 µg/L and 0.5 µg/L, respectively. FEN and/or NRFEN were detected in 44 and 59 UR specimens, respectively, and FEN in 46 OF specimens (43 OF+UR+, 3 OF+UR-, 16 OF-UR+, and 249 OF-UR-). In UR there were no instances with FEN positive and NORFEN negative. UR creatinine was <20 mg/dL in the 3 OF+UR- specimen pairs. The median OF/UR analyte concentration ratios in positive sample pairs were 0.23 for OF FEN/UR FEN and 0.02 for OF FEN/UR NRFEN.

CONCLUSIONS

We demonstrate that UR detects more FEN use than OF in an AMP setting when UR FEN and UR NORFEN LODs of 2.0 µg/L are used. OF is less sensitive than UR in detecting FEN use, but is still valuable for cases with low UR creatinine and/or suspected adulteration or substitution of UR. The UR vs OF comparison statistics are greatly impacted by even minimal adjustments of the LOD.

Determination of Fentanyl, Alpha-Methylfentanyl, Beta-Hydroxyfentanyl, and the Metabolite Norfentanyl in Rat Urine by LC-MS/MS

Fentanyl and its analogs are potent synthetic opioids with a high potential for abuse and dependence. They have become major contributors to opioid deaths. This study aimed to determine whether the metabolites of fentanyl, alpha-methylfentanyl and beta-hydroxyfentanyl, excreted in the urine, can demonstrate historical drug exposure. Fentanyl is primarily metabolized via CYP3A4 into norfentanyl, although there is little research on its metabolism into alpha-methylfentanyl and beta-hydroxyfentanyl. We conducted in vitro experiments with human liver microsomes (HLM) and rat liver microsomes (RLM) to elucidate the major metabolic pathways of alpha-methylfentanyl and beta-hydroxyfentanyl using UHPLC coupled with mass spectrometry. The results showed that both alpha-methylfentanyl and beta-hydroxyfentanyl were predominantly metabolized into norfentanyl in HLM and RLM. Urine samples were collected at different intervals from 0 h to 72 h after intravenous administration of alpha-methylfentanyl and beta-hydroxyfentanyl (20 μg/kg) to Sprague-Dawley rats. We prepared the samples by liquid-liquid extraction, and the internal standard (IS) was cariprazine. A sensitive, rapid LC-MS/MS method was developed and validated to determine four analytes in the urine. The lower limit of qualification (LLOQ) in urine was 2 pg/ml for fentanyl, 5 pg/ml for alpha-methylfentanyl, 10 pg/ml for beta-hydroxyfentanyl, and 40 pg/ml for norfentanyl. The analytical range was 0.002-2 ng/ml for fentanyl, 0.005-5 ng/ml for alpha-methylfentanyl, 0.01-10 ng/ml for beta-hydroxyfentany and 0.04-40 ng/ml for norfentanyl. All analytes demonstrated good linearity (R2 > 0.99). The extraction recoveries were in the 67.8%-92.1% range, and the IS-normalized matrix effects were between 55.5%-74.0% (CV < 15%). Our data indicated that norfentanyl has a higher concentration in rat urine and was detectable for at least three days after exposure to these compounds. This developed method may be useful in various fields, including forensic analysis, workplace drug testing, and monitoring drug abuse.

Pharmacokinetics of fentanyl citrate and norfentanyl in Holstein calves and effect of analytical performances on fentanyl parameter estimation

This study describes the pharmacokinetics of intravenously administered (i.v.) fentanyl citrate, and its primary metabolite norfentanyl in Holstein calves. Eight calves (58.6 ± 2.2 kg), aged 3-4 weeks, were administered fentanyl citrate at a single dose of 5.0 μg/kg i.v. Blood samples were collected from 0 to 24 hr. Plasma (nor)fentanyl concentrations were determined using liquid chromatography with mass spectrometry and a lower limit of quantification (LLOQ) of 0.03 ng/ml. To explore the effect of analytical performance on fentanyl parameter estimation, the noncompartmental pharmacokinetic analysis was then repeated with a hypothetical LLOQ value of 0.05 ng/ml. Terminal elimination half-life was estimated at 12.7 and 3.6 hr for fentanyl and norfentanyl, respectively. For fentanyl, systemic clearance was estimated at 2.0 L hr^-1  kg^-1 , volume of distribution at steady-state was 24.8 L/kg and extraction ratio was 0.42. At a hypothetical LLOQ of 0.05 ng/ml fentanyl half-life, volume of distribution at steady-state and clearance were, respectively, of 3.0 hr, 8.8 L/kg and 3.4 L kg^-1  hr^-1 . Fentanyl citrate administered i.v. at 5.0 μg/kg can reach levels associated with analgesia in other species. Pharmacokinetic parameters should be interpreted with respect to LLOQ, as lower limits can influence estimated parameters, such as elimination half-life or systemic clearance and have significant impact on dosage regimen selection in clinical practice.

Could chest wall rigidity be a factor in rapid death from illicit fentanyl abuse?

BACKGROUND

There has been a significant spike in fentanyl-related deaths from illicit fentanyl supplied via the heroin trade. Past fentanyl access was primarily oral or dermal via prescription fentanyl patch diversion. One factor potentially driving this increase in fatalities is the change in route of administration. Rapid intravenous (IV) fentanyl can produce chest wall rigidity. We evaluated post-mortem fentanyl and norfentanyl concentrations in a recent surge of lethal fentanyl intoxications.

METHODS

Fentanyl related deaths from the Franklin County coroner's office from January to September 2015 were identified. Presumptive positive fentanyl results were confirmed by quantitative analysis using liquid chromatography tandem mass spectrometry (LC/MS/MS) and were able to quantify fentanyl, norfentanyl, alfentanyl, and sufentanyl.

RESULTS

48 fentanyl deaths were identified. Mean fentanyl concentrations were 12.5 ng/ml, (range 0.5 ng/ml to >40 ng/ml). Mean norfentanyl concentrations were 1.9 ng/ml (range none detected to 8.3 ng/ml). No appreciable concentrations of norfentanyl could be detected in 20 of 48 cases (42%) and were less than 1 ng/ml in 25 cases (52%). Elevated fentanyl concentrations did not correlate with rises in norfentanyl levels. In several cases fentanyl concentrations were strikingly high (22 ng/ml and 20 ng/ml) with no norfentanyl detected.

DISCUSSION

The lack of any measurable norfentanyl in half of our cases suggests a very rapid death, consistent with acute chest rigidity. An alternate explanation could be a dose-related rapid onset of respiratory arrest. Deaths occurred with low levels of fentanyl in the therapeutic range (1-2 ng/ml) in apparent non-naïve opiate abusers. Acute chest wall rigidity is a well-recognized complication in the medical community but unknown within the drug abuse community. The average abuser of illicit opioids may be unaware of the increasing fentanyl content of their illicit opioid purchase.

CONCLUSION

In summary we believe sudden onset chest wall rigidity may be a significant and previously unreported factor leading to an increased mortality, from illicit IV fentanyl use. Fentanyl and norfentanyl ratios and concentrations suggest a more rapid onset of death given the finding of fentanyl without norfentanyl in many of the fatalities. Chest wall rigidity may help explain the cause of death in these instances, in contrast to the typical opioid-related overdose deaths. Intravenous heroin users should be educated regarding this potentially fatal complication given the increasingly common substitution and combination with heroin of fentanyl.