UMass Chan Medical School Faculty Publications


Sentanyl: a comparison of blood fentanyl concentrations and naloxone dosing after non-fatal overdose

UMMS Affiliation

Department of Emergency Medicine, Division of Medical Toxicology

Publication Date


Document Type



Emergency Medicine | Medical Toxicology | Substance Abuse and Addiction | Toxicology


INTRODUCTION: Non-pharmaceutical fentanyl and its analogs have driven striking increases in opioid-associated overdose deaths. These highly potent opioids can be found at low concentrations in biological specimens. Little is known regarding the concentrations of these substances among survivors of non-fatal overdoses. In a locale where fentanyl is responsible for the majority of non-fatal opioid overdoses, we compared the concentration of fentanyl in blood to naloxone dosing in the presence and absence of a concurrent sedative-hypnotic exposure.

METHODS: In this pilot study, we enrolled adult patients presenting to the emergency department (ED) who: (1) arrived after an overdose requiring naloxone for the reversal of respiratory depression; and (2) who required venipuncture or intravenous access as part of their clinical care. Blood specimens (n = 20) underwent comprehensive toxicology testing, including the quantitation of fentanyl, fentanyl analogs, and naloxone, as well as the detection of common sedative-hypnotics and a wide range of other illicit and pharmaceutical substances. We then compared fentanyl concentrations to naloxone dosing in participants with and without a concomitant sedative-hypnotic exposure.

RESULTS: Nineteen of twenty participants (95%) were exposed to fentanyl prior to their overdose; the remaining participant tested positive for heroin metabolites. No participants reported pharmaceutical fentanyl use. Fentanyl analogs - acetylfentanyl or carfentanil - were present in three specimens. In 11 cases, fentanyl and its metabolites were the only opioids identified. Among the fentanyl-exposed, blood concentrations ranged from < 0.1-19 ng/mL with a mean of 6.2 ng/mL and a median of 3.6 ng/mL. There was no relationship between fentanyl concentration and naloxone dose administered for reversal. We detected sedative-hypnotics (including benzodiazepines, muscle relaxants, and antidepressants) in nine participants. Among the sedative-hypnotic exposed, fentanyl concentrations were lower, but naloxone dosing was similar to those without a concomitant exposure.

CONCLUSIONS: In this study, we found that: 1) fentanyl was present in the blood of nearly all participants; 2) fentanyl concentrations were lower among study participants with concomitant sedative-hypnotic exposure; and 3) the dose of naloxone administered for overdose reversal was not associated with the measured fentanyl concentration in blood specimens. Our results underscore the role that tolerance and concomitant drug exposure play in the precipitation and resuscitation of management of opioid overdose.


Fentanyl, naloxone, novel psychoactive, opioid, overdose

DOI of Published Version



Krotulski AJ, Chapman BP, Marks SJ, Ontiveros ST, Devin-Holcombe K, Fogarty MF, Trieu H, Logan BK, Merchant RC, Babu KM. Sentanyl: a comparison of blood fentanyl concentrations and naloxone dosing after non-fatal overdose. Clin Toxicol (Phila). 2021 Jul 19:1-8. doi: 10.1080/15563650.2021.1948558. Epub ahead of print. PMID: 34278904. Link to article on publisher's site

Related Resources

Link to Article in PubMed

Journal/Book/Conference Title

Clinical toxicology (Philadelphia, Pa.)

PubMed ID