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Background: The availability of central nervous system stimulants has risen in recent years, along with increased dispensing of stimulants for treatment of, for example, parent-reported attention-deficit/hyperactivity disorder in children and new diagnoses during adulthood. Typologies of drug use, as has been done with opioids, fail to include a sufficient range of behavioral factors to contextualize person-centric circumstances surrounding drug use. Understanding these patterns across drug classes would bring public health and regulatory practices toward precision public health., Objective: The objective of this study was to quantitatively delineate the unique behavioral profiles of adults who currently nonmedically use stimulants and opioids using a latent class analysis and to contrast the differences in findings by class. We further evaluated whether the subgroups identified were associated with an increased Drug Abuse Screening Test-10 (DAST-10) score, which is an indicator of average problematic drug use., Methods: This study used a national cross-sectional web-based survey, using 3 survey launches from 2019 to 2020 (before the COVID-19 pandemic). Data from adults who reported nonmedical use of prescription stimulants (n=2083) or prescription opioids (n=6127) in the last 12 months were analyzed. A weighted latent class analysis was used to identify the patterns of use. Drug types, motivations, and behaviors were factors in the model, which characterized unique classes of behavior., Results: Five stimulant nonmedical use classes were identified: amphetamine self-medication, network-sourced stimulant for alertness, nonamphetamine performance use, recreational use, and nondiscriminatory behaviors. The drug used nonmedically, acquisition through a friend or family member, and use to get high were strong differentiators among the stimulant classes. The latter 4 classes had significantly higher DAST-10 scores than amphetamine self-medication (P<.001). In addition, 4 opioid nonmedical use classes were identified: moderate pain with low mental health burden, high pain with higher mental health burden, risky behaviors with diverse motivations, and nondiscriminatory behaviors. There was a progressive and significant increase in DAST-10 scores across classes (P<.001). The potency of the opioid, pain history, the routes of administration, and psychoactive effect behaviors were strong differentiators among the opioid classes., Conclusions: A more precise understanding of how behaviors tend to co-occur would improve efficacy and efficiency in developing interventions and supporting the overall health of those who use drugs, and it would improve communication with, and connection to, those at risk for severe drug outcomes., (©Karilynn M Rockhill, Richard Olson, Richard C Dart, Janetta L Iwanicki, Joshua C Black. Originally published in the Journal of Medical Internet Research (https://www.jmir.org), 20.09.2023.)

Objective: Tapentadol is an atypical opioid analgesic thought to have dual mechanisms of action: µ-receptor agonism and inhibition of norepinephrine reuptake. Unlike other atypical opioids, tapentadol is a schedule II-controlled substance. We compared the prevalence of abuse (use to get high) of tapentadol to other atypical opioids used to treat pain (buprenor-phine and tramadol)., Design: An observational, serial cross-sectional study., Setting: Individuals enrolling in treatment programs for opioid use disorder in 2019. Each completed a self-administered, paper questionnaire assessing prescription drug abuse and illegal drug use within 1 week of enrollment., Main Outcome Measures: Indication of past month abuse of tapentadol or comparator drugs on a self-administered ques-tionnaire., Results: There were 6,987 respondents. Unadjusted and utilization-adjusted logistic regression models were used to compare odds of endorsement of tapentadol to tramadol and buprenorphine products indicated for the management of pain. Unadjusted abuse prevalence was 0.20 percent for total tapentadol (0.03 percent for NUCYNTA® and 0.06 percent for NUCYNTA ER). Relative to total tapentadol, the odds of abuse of buprenorphine for pain was 2.9 times greater (95 percent CI: 1.6 to 5.3, p < 0.001), and for tramadol, 43.1 times greater (95 percent CI: 25.3 to 73.3, p < 0.001). Adjusting for prescriptions dispensed, differences in odds of abuse were not statistically significant (odds ratio (OR) = 1.6, 95 per-cent CI: 0.9 to 3.0, p = 0.108 for buprenorphine for pain and OR = 0.7, 95 percent CI: 0.4 to 1.2, p = 0.209 for tramadol)., Conclusions: Tapentadol use to get high is less frequent than other atypical opioids. Findings suggest tapentadol is rarely the primary drug abused by an individual.

Background: Fentanyl-related deaths continue to increase in the United States; however, most national studies focus on fatal overdose. More research, including data on nonfatal overdose, is needed. Objective: We examined trends in characteristics of fatal and nonfatal fentanyl-related poisonings ("exposures") in the US. Methods: National Poison Control data were examined to estimate trends in characteristics of reported exposures between 2015 and 2021 (N = 15,391; 38.7% female). We also delineated correlates of experiencing a major adverse effect or death. Results: The proportion of exposures increased among all age groups between ages 13 and 39 (ps < .05) with the largest increase among those age 13-19 (a 127.8% increase). With respect to reasons for use, the proportion of cases involving fentanyl "abuse" increased by 63.8% ( p  < .001). The proportion involving fentanyl inhalation increased 427.6% from 5.7% to 29.9% and injection increased from 6.7% to 9.6%, a 42.3% increase (ps < .01). The proportion also increased for co-use of methamphetamine (by 669.0%), cocaine (by 374.0%), and heroin (by 159.5%). The proportion of major adverse effects increased from 15.5% to 39.6% ( p  < .001). In the multivariable model, "abuse", suspected suicide attempts, and use via inhalation were risk factors for experiencing a major effect or death, and misuse, ingestion, dermal use, and co-use of methamphetamine were associated with lower risk. Conclusion: Poison Control data suggest that characteristics of individuals exposed to fentanyl continue to shift, with use via inhalation increasing and medical outcomes of nonfatal poisonings becoming more severe. These results complement mortality data and inform prevention and harm reduction efforts.

Purpose: To investigate the prevalence of non-medical use (NMU) of codeine in Germany, Italy, Spain and the UK and whether availability of OTC codeine has any association with NMU of the drug., Methods: Data collected in the online Survey of Non-Medical Use of Prescription Drugs, in surveys launched in the second half of 2018 from (Germany (n = 14,969), Italy, (n = 9974), Spain (n = 9912) and the UK (n = 9819) were analysed. For each survey, the estimated prevalence and 95% confidence interval (CI) of respondents reporting NMU of prescription and/or OTC codeine within the last 12 months were calculated and compared., Results: The prevalence of last 12-month NMU in Spain was 12.6% (95% CI 11.7-13.6) for prescription codeine, 6.3% (5.6-7.0) for OTC codeine and 16.1% (15.1-17.3) for any codeine (prescription and/or OTC). The prevalence of last 12-month NMU in the UK was 5.4% (4.9-5.8) for prescription codeine, 4.5% (4.1-5.0) for OTC codeine and 8.3% (7.8-8.9) for any codeine (prescription and/or OTC). The prevalence of last 12-month NMU for prescription codeine was 2.1% (1.9-2.4) in Germany and 1.9% (1.7-2.2) in Italy., Conclusion: The prevalence of last 12-month NMU of any codeine product is approximately eight times greater in Spain and four times greater in the UK compared to Germany and Italy where the drug is only available by prescription. While other factors may contribute, these findings suggest that availability of codeine OTC is associated with greater NMU., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Background: In 2014, the Drug Enforcement Administration rescheduled hydrocodone combination products to Schedule II to reduce nonmedical use and diversion., Methods: The impact of rescheduling was assessed using quarterly data from 2011 through 2019 from the Researched Abuse, Diversion and Addiction-Related Surveillance (RADARS ® ) System Poison Center Program and IQVIA TM Longitudinal Prescription Data. Trends and immediate changes in prescriptions dispensed and misuse exposures before and after rescheduling involving hydrocodone, oxycodone, and other Schedule II opioid analgesics were calculated using segmented regression., Results: Hydrocodone prescriptions were stable pre-rescheduling, decreased by 2.7% (95% CI: -3.6%, -1.8%, p  < 0.0001) per quarter post-rescheduling. Misuse exposures involving hydrocodone were decreasing by 3.2% (95% CI: -3.9%, -2.4%, p  < 0.0001) per quarter pre-rescheduling and decreased by 4.9% (95% CI: -5.5%, -4.2%, p  < 0.0001) post-rescheduling. Immediate decreases in hydrocodone prescriptions and misuse exposure rates in 2014Q4 compared to 2014Q3 were significant and different from oxycodone or other Schedule II opioids. Schedule II opioid analgesics prescriptions in aggregate were stable prior to rescheduling, decreased by 10.8% (95%CI: -14.0%, -7.6%, p  < 0.0001) immediately after the rescheduling, and decreased by 2.3% per quarter (95% CI: -3.1%, -1.5%, p  < 0.0001) subsequently. Misuse exposures involving these opioids were decreasing by 3.3% (95% CI: -4.1%, -2.5%, p  < 0.0001) prior to rescheduling then by 2.8%, (95% CI: -3.4%, -2.2%, p  < 0.0001) after rescheduling. The immediate change in misuse was not significant., Conclusions: Rescheduling corresponded with changes in hydrocodone prescribing and misuse not offset by increases in other Schedule II opioid analgesics. Misuse exposures for hydrocodone and comparators were decreasing prior to rescheduling with little change post-intervention.

Background: Opioid use disorder and its consequences are a persistent public health concern for Australians. Web activity has been used to understand the perception of drug safety and diversion of drugs in contexts outside of Australia. The anonymity of the internet offers several advantages for surveilling and inquiring about specific covert behaviors, such as diversion or discussion of sensitive subjects where traditional surveillance approaches might be limited., Objective: This study aims to characterize the content of web posts and compare reports of illicit sales of tapentadol and oxycodone from sources originating in Australia. First, post content is evaluated to determine whether internet discussion encourages or discourages proper therapeutic use of the drugs. Second, we hypothesize that tapentadol would have lower street price and fewer illicit sales than oxycodone., Methods: Web posts originating in Australia between 2017 and 2019 were collected using the Researched Abuse, Diversion, and Addiction-Related Surveillance System Web Monitoring Program. Using a manual coding process, unstructured post content from social media, blogs, and forums was categorized into topics of discussion related to the harms and behaviors that could lead to harm. Illicit sales data in a structured format were collected through a crowdsourcing website between 2016 and 2019 using the Researched Abuse, Diversion, and Addiction-Related Surveillance System StreetRx Program. In total, 2 multivariable regression models assessed the differences in illicit price and number of sales., Results: A total of 4.7% (28/600) of tapentadol posts discussed an adverse event, whereas 10.27% (95% CI 9.32-11.21) of oxycodone posts discussed this topic. A total of 10% (60/600) of tapentadol posts discussed unsafe use or side effects, whereas 20.17% (95% CI 18.92-21.41) of oxycodone posts discussed unsafe use or side effects. There were 31 illicit sales reports for tapentadol (geometric mean price per milligram: Aus $0.12 [US $0.09]) and 756 illicit sales reports for oxycodone (Aus $1.28 [US $0.91]). Models detected no differences in the street price or number of sales between the drugs when covariates were included, although the potency of the pill significantly predicted the street price (P<.001) and availability predicted the number of sales (P=.03)., Conclusions: Australians searching the web for opinions could judge tapentadol as safer than oxycodone because of the web post content. The illicit sales market for tapentadol was smaller than that of oxycodone, and drug potency and licit availability are likely important factors influencing the illicit market., (©Joshua Black, Zachary R Margolin, Gabrielle Bau, Richard Olson, Janetta L Iwanicki, Richard C Dart. Originally published in JMIR Public Health and Surveillance (https://publichealth.jmir.org), 20.12.2021.)

Aims: Prescription drug misuse in the USA increased during the 1990s to 2010. The epidemic stimulated the need new analytical strategies and techniques to understand the medications involved, user characteristics and other factors needed to address the epidemic., Methods: A strategy of mosaic surveillance has evolved. Using real world evidence, the goal is to paint a more complete profile of a drug's real world misuse using triangulation-integrating results from multiple sources, where each approach has unrelated sources of bias., Results: Research findings have been remarkably consistent across multiple data sources. The most commonly misused opioid medications: hydrocodone = oxycodone > methadone = buprenorphine = tramadol = fentanyl (prescription form) > morphine > hydromorphone = oxymorphone > tapentadol. This rank order is similar to the number of prescriptions dispensed for each product in the USA. In the USA, prescription opioid misuse started to decrease about 2011. Typically, multiple drugs are misused together, particularly in lethal cases. Immediate release formulations are more commonly misused than extended release formulations. The introduction of tamper resistant formulations to resist crushing were followed by a decrease in misuse of those products., Conclusions: The rapid expansion of opioid prescribing was accompanied by increasing misuse and mortality. Interventions such as prescription drug monitoring programmes, increased law enforcement and abuse deterrent formulations have been followed by decreases in misuse of most opioid analgesics., (© 2021 British Pharmacological Society.)

Background and Aims: Mitragyna speciosa ('kratom') contains mu opioid partial agonists. It is widely available, and occasionally used as a home remedy for opioid use disorder. The Drug Enforcement Agency considers kratom a drug of concern; however, prevalence of use and role in drug misuse are unknown. This study aimed to characterize kratom use in the United States., Design: Cross-sectional Survey of Non-Medical Use of Prescription Drugs (NMURx) Program, 2018 third quarter and 2019 first quarter., Setting: A validated non-probability online survey in the United States., Participants: A total of 59 714 respondents aged 18 years or older, weighted to represent the adult US population (n = 252 063 800)., Measurements: In addition to prevalence of past-year kratom and other drug use, behavior proportions were estimated. The Drug Abuse Screening Test (DAST-10) estimated consequences of drug abuse., Findings: The estimated prevalence of past-year kratom use in the adult US population was 0.8% [95% confidence interval (CI) = 0.7-0.9], representing 2 031 803 adults. Life-time prevalence was 1.3% (95% CI = 1.2-1.4), representing 3 353 624 adults. Kratom users were younger (mean 35 years, P < 0.001), with higher proportions of males (61.0 versus 48.6%, P < 0.001), students (14.1 versus 7.5%, P < 0.001) and health-care professionals (9.7 versus 4.5%, P < 0.001) and fewer bachelor's/advanced degree graduates (33.4 versus 42.6%, P < 0.001) compared with non-users. Results were inconclusive on whether there was a difference in kratom use by race, household income or employment status. Among those with past-year kratom use, 36.7% (95% CI = 32.1-41.3) non-medically used prescription opioids, 21.7% (95% CI = 18.0-25.5) used illicit opioids, 54.4% (95% CI = 49.5-59.3) used another illicit drug and 67.1% (95% CI = 62.5-71.8) used cannabis. The DAST-10 profile was more often substantial/severe in kratom users (21 versus 1%, P < 0.001) compared with non-users., Conclusions: Estimated United States past-year prevalence of kratom use is 0.8%, and kratom users tend to have more serious substance abuse profiles than non-users or users of cannabis, alcohol or cigarettes. To our knowledge, this is the first description of kratom use at the national level., (© 2020 Society for the Study of Addiction.)

Objective: To evaluate abuse, misuse, and diversion of Xtampza ER, an extended-release (ER) abuse-deterrent formulation (ADF) of oxycodone., Methods: Abuse, misuse, and diversion of Xtampza ER were assessed using Researched Abuse, Diversion and Addiction-Related Surveillance (RADARS) System data sources. Xtampza ER was compared with immediate-release (IR) oxycodone, other ADF ER products combined, and non-ADF ER products combined., Results: Xtampza ER prescriptions increased 50-fold during the study period. In contrast, cases from poison centers, substance abuse treatment centers, and diversion were infrequent and did not increase. Adjusted for prescriptions dispensed, poison center exposures were greater for IR oxycodone (rate ratio [RR] = 2.3, P = 0.008), other ADF ER opioids (RR = 5.2, P < 0.001), and non-ADF ER opioids (RR = 2.5, P = 0.004) than for Xtampza ER. In Treatment Center Programs Combined, past-month abuse prevalence for other ADF ER opioids (odds ratio [OR] = 7.4, P < 0.001) and non-ADF ER opioids (OR = 2.0, P = 0.002) was greater than Xtampza ER; IR oxycodone was not significantly different (OR = 1.2, P = 0.349). In the Drug Diversion Program, rates for IR oxycodone (RR = 3.7, P = 0.003), other ADF ER opioids (RR = 4.2, P = 0.002), and non-ADF ER opioids (RR = 3.4, P = 0.007) were greater than Xtampza ER. Adjustment using morphine equivalents provided similar results, except that IR oxycodone in Treatment Center Programs Combined became higher than Xtampza ER. Nonoral abuse cases involving Xtampza ER were infrequent; Web monitoring data support findings that Xtampza ER is difficult to abuse nonorally., Conclusion: Xtampza ER abuse, misuse, and diversion and tampering are low relative to other prescription opioid analgesics. Abuse and diversion did not increase over the study period., (© The Author(s) 2020. Published by Oxford University Press on behalf of the American Academy of Pain Medicine.)

Background: Understanding prescription medication misuse is challenging due to lack of consistent measures of misuse behaviors and prevalence between countries. Tramadol is an atypical opioid with a dual mechanism, and has low drug liking compared to conventional opioids. We evaluate tramadol misuse compared to conventional opioids utilizing a harmonized validated national survey across four countries: Germany, Italy, Spain, and the United Kingdom (UK)., Methods: Data from the Survey of Non-Medical Use of Prescription Drugs (NMURx) Program online cross-sectional general population national surveys are analyzed from 2018 from four countries, with 45,000 total responses. Misuse and abuse of tramadol, codeine, morphine, and oxycodone are compared, and national prevalence estimates calculated via calibration weighting. Rates are calculated per population and per drug availability. Supplemental data are included from patients entering treatment centres and poison centre exposures., Results: In 2018, distribution, misuse, and abuse of four prescription opioids show similar patterns across four countries. In all countries, codeine is misused by the largest number of adults (estimated 861,181 in Italy to 4,676,680 in Spain in past 12 months). When adjusted for availability, tramadol is misused uncommonly with lowest or second lowest rates in all countries. Most abuse occurs by the oral route for all opioids, including tramadol with only 7.27 (Germany) to 54.92 (UK) cases per 100,000 units sold., Conclusions: In four countries, tramadol misuse and abuse are infrequent both in absolute number of cases and in comparison to conventional opioids. Even with availability of intravenous tramadol formulations, misuse by injection is rare., (Copyright © 2020 The Author(s). Published by Elsevier B.V. All rights reserved.)

Objectives: To determine the association between poison center opioid exposure calls and National Vital Statistics System (NVSS) deaths., Methods: We categorized Centers for Disease Control and Prevention NVSS mortality and the Researched Abuse, Diversion and Addiction-Related Surveillance System poison center program cases from 2006 to 2016 by International Classification of Diseases, Tenth Revision, codes (heroin [T40.1]; natural or semisynthetic opioids [T40.2]; methadone [T40.3]; synthetic opioids, other than methadone [T40.4]). We scaled rates by 100 000 population and calculated Pearson correlation coefficients. Sensitivity analysis excluded polysubstance cases involving either heroin or synthetic opioids as well as natural and semisynthetic opioids., Results: The NVSS mortality and poison center program exposure rates showed similar trends from 2006 to 2012, and diverged after 2012 for all opioids combined, natural and semisynthetic opioids, and synthetic opioids (r = -0.37, -0.12, and 0.30, respectively). Sensitivity analysis with removal of heroin or synthetic opioid polysubstance deaths markedly improved correlations for all opioids combined and natural and semisynthetic opioids (r = 0.87 and 0.36, respectively)., Conclusions: The NVSS mortality and poison center exposure rates showed similar trends from 2006 to 2012 then diverged, with sensitivity analysis suggesting polysubstance cases also involving heroin or illicit fentanyl as the cause. Public Health Implications. The NVSS and poison center program may provide complementary data when trends diverge. Public health interventions must include both licit and illicit opioids for maximal impact.

Objective: We performed a systematic review to answer the question, "Does the introduction of an opioid analgesic with abuse deterrent properties result in reduced overall abuse of the drug in the community?", Design: We included opioid analgesics with abuse deterrent properties (hydrocodone, morphine, oxycodone) with results restricted to the metasearch term "delayed onset," English language, use in humans, and publication years 2009-2016. All articles that contained data evaluating misuse, abuse, overdose, addiction, and death were included. The results were categorized using the Bradford-Hill criteria., Results: We included 44 reports: hydrocodone (n = 7), morphine (n = 5), or oxycodone (n = 32) with Food and Drug Administration-approved Categories 1, 2, or 3 abuse deterrent labeling. The data currently available support the Hill criteria of strength (effect size), consistency (reproducibility), temporality, plausibility, and coherence. There was insufficient or no information available for the criteria of biological gradient, experiment, and analogy. We also assessed confounding factors and bias, which indicated that both were present and substantial in magnitude., Conclusions: Our analysis found that only oxycodone extended release (ER) had information available to evaluate abuse deterrence in the community. In Australia, Canada, and the United States, reformulation of oxycodone ER was followed by marked reduction in measures of abuse. The precise extent of reduced abuse cannot be calculated because of heterogeneous data sets, but the reported reductions ranged from 10 to 90 percent depending on the measure and the duration of follow-up.

Background: Therapeutic use and abuse of prescription opioids in the United States increased substantially between 1990 and 2010. The Centers for Disease Control estimated deaths related to pharmaceutical opioids reached nearly 19,000 in 2014. Of prescription opioids sold, 10% are extended release (ER) and 90% immediate release (IR). However, most regulations and interventions have focused on decreasing ER abuse. Our objective was to compare rates of abuse and diversion of ER and IR opioid analgesics over time using multiple surveillance programs., Methods: Rates of abuse and diversion of ER and IR opioid formulations were compared using data from four surveillance programs in the Researched Abuse, Diversion and Addiction Related Surveillance (RADARS®) System. Data were evaluated from 2009 through 2015, and Poisson regression used to compare IR and ER opioid cases over time., Results: From 2009 to 2015, IR opioids were prescribed at a rate 12 to 16 times higher than ER. In the Poison Center Program, population-adjusted rates of Intentional Abuse for IR were 4.6 fold higher than ER opioids (p<0.001). In the Drug Diversion Program, population-adjusted rates of diversion were 6.1 fold higher for IR than ER opioids (p<0.001). In the Opioid Treatment Program, population-adjusted rates of endorsements for abuse were 1.6 fold higher for IR opioids than ER (p = 0.002). In the Survey of Key Informants' Patients Program, population-adjusted rates of endorsements for abuse were 1.5 fold higher for IR opioids than ER (p<0.001)., Conclusions: Between 2009 and 2015, IR opioids were prescribed at a much higher rate than ER opioids. Results from four surveillance programs show population-adjusted rates of prescription opioid abuse were markedly higher for IR than ER medications. For the greatest public health benefit, future interventions to decrease prescription opioid abuse should focus on both IR and ER formulations., Competing Interests: The authors have declared that no additional competing interests exist.

Context: Lacosamide treats partial seizures by enhancing slow inactivation of voltage-gated sodium channels. The described cardiac toxicity of lacosamide in the literature to date includes atrioventricular blockade (PR prolongation), atrial flutter, atrial fibrillation, sinus pauses, ventricular tachycardia and a single cardiac arrest. We report a second case of cardiac arrest following an intentional lacosamide overdose., Case Details: A 16 year-old female with a seizure disorder was found unresponsive in pulseless ventricular tachycardia after intentionally ingesting 4.5 g (76 mg/kg) lacosamide, 120 mg (2 mg/kg) cyclobenzaprine and an unknown amount of levetiracetam. Exact time of ingestion was unknown. Her initial electrocardiogram (ECG) demonstrated sinus tachycardia at 139 beats per minute, QRS duration 112 ms, and terminal R-wave in lead aVR > 3 mm. Despite treatment with 150 mEq of sodium bicarbonate, she had persistent EKG findings eight hours after presentation. Her serum lacosamide concentration nine hours after presentation was elevated at 22.8 μg/mL, while serum cyclobenzaprine concentration was 16 ng/mL (therapeutic: 10-30 ng/mL), and serum levetiracetam concentration was 22.7 μg/mL (therapeutic: 12-46 μg/mL). On hospital day three, ECG demonstrated resolution of the terminal R-wave with QRS of 78 ms. The patient recovered without physical or neurologic sequelae., Discussion: The patient's lacosamide, cyclobenzaprine and levetiracetam overdose was associated with QRS prolongation and terminal right axis deviation--suggesting sodium channel blockade as a likely etiology for her cardiac arrest. Cyclobenzaprine has potential for sodium channel blockade and ventricular dysrhythmias although cardiac toxicity due to cyclobenzaprine alone is rare. The combination of cyclobenzaprine with lacosamide may have resulted in cardiovascular collapse. In conclusion, overdose of lacosamide combined with therapeutic concentrations of sodium channel blocking xenobiotics may cause cardiac conduction delays and cardiac arrest.

In acute lung injuries, secretory phospholipase A(2) (sPLA(2)) inhibits surfactants by hydrolyzing phospholipids. Because hyaluronan (HA) reduces hydrolysis of phospholipids by sPLA(2), and because sPLA(2) inhibits surfactant in vitro, the authors hypothesized HA would reduce sPLA(2) inhibition. Surfactants were used alone or mixed with HA and/or sPLA(2) then tested for surface activity in 2 separate assays, or for sPLA(2) activity. Equilibrium surface pressures were identical for surfactant with or without HA. sPLA(2) inhibited surface activity but this inhibitory effect was reduced with HA by 14% in the spreading trough and by 63% in a modified bubble surfactometer. Hyaluronan caused a modest reduction (39%) of sPLA(2) breakdown of labeled phospholipid. Therefore hyaluronan reduces inhibition of surfactants by sPLA(2) in vitro, and reduces the activity of the enzyme.