Effect of Cocaine Use on Methadone Pharmacokinetics in Humans

"Coke in the Dope": The Underrecognized Complications of a Cocaine-Adulterated Fentanyl Supply

ABSTRACT

The opioid crisis, particularly the "fourth wave" involving fentanyl and stimulants, has been responsible for an alarming increase in overdose deaths in the United States. Although fentanyl contamination in cocaine has gained significant attention, the converse-cocaine-adulterated fentanyl-has been largely overlooked despite its health implications. The rise in concurrent cocaine and fentanyl overdose deaths could be attributed to various factors, from intentional polysubstance use to unintentional adulterations. Cocaine-related health issues may amplify the problem. Four potential pathways for the increased risk of overdose with cocaine-adulterated opioids include enhanced drug reinforcement, potential overdose risk with switching drug samples, altered metabolism of medications used for opioid use disorder, and increased myocardial demand juxtaposed with opioid-induced respiratory depression. With these risks, the importance of drug testing becomes paramount in the unregulated drug market. As polysubstance use overdoses surge, there is an urgent need to understand how drug supplies are changing in order to effectively identify appropriate harm reduction strategies. Specifically, further research is needed evaluating complications of low-level cocaine exposure with chronic/persistent opioid use. The hazards associated with cocaine-adulterated fentanyl emphasize the significance of understanding not only fentanyl's presence in cocaine but also cocaine's role in the fentanyl supply.

Levomethadone Therapeutic Drug Monitoring to Aid Opioid Withdrawal Therapy: A Short Communication

BACKGROUND

Therapeutic drug monitoring (TDM) is recommended for opioid maintenance therapy with levomethadone. However, TDM has not yet been applied to monitor opioid withdrawal therapy clinically, although tools to improve it are required.

METHODS

In this observational cohort study, repeated TDM with levomethadone was performed according to a prospective opioid withdrawal study protocol. Objective and subjective opioid withdrawal symptoms were measured using validated rating scales and correlated to levomethadone plasma concentrations. Plasma levels were measured using high-pressure liquid chromatography with column switching and spectroscopic detection of methadone and its major metabolite.

RESULTS

This study included 31 opioid-dependent patients who participated in standardized opioid withdrawal therapy. The serum levels of levomethadone were found to be highly variable and below the recommended therapeutic reference range of 250 ng/mL for maintenance therapy. These serum levels were positively correlated with dosage (r = 0.632; P < 0.001) and inversely correlated with subjective (r = -0.29; P = 0.011) and objective (r = -0.28; P = 0.014) withdrawal symptoms.

CONCLUSIONS

The evidence provided sheds light on how to improve levomethadone withdrawal therapy in patients with opioid dependence. It seems likely that higher initial doses at the beginning and lower dose reductions would have been advantageous. TDM can enhance the safety of opioid withdrawal therapies, minimize withdrawal symptoms, and reduce dropout rates.

Pharmacogenetics of Lethal Opioid Overdose: Review of Current Evidence and Preliminary Results from a Pilot Study

There has been a worldwide substantial increase in accidental opioid-overdose deaths. The aim of this review, along with preliminary results from our pilot study, is to highlight the use of pharmacogenetics as a tool to predict causes of accidental opioid-overdose death. For this review, a systematic literature search of PubMed^® between the time period of January 2000 to March 2023 was carried out. We included study cohorts, case-controls, or case reports that investigated the frequency of genetic variants in opioid-related post-mortem samples and the association between these variants and opioid plasma concentrations. A total of 18 studies were included in our systematic review. The systematic review provides evidence of the use of CYP2D6, and to a lower extent, CYP2B6 and CYP3A4/5 genotyping in identifying unexpectedly high or low opioid and metabolite blood concentrations from post-mortem samples. Our own pilot study provides support for an enrichment of the CYP2B6*4-allele in our methadone-overdose sample (n = 41) compared to the anticipated frequency in the general population. The results from our systematic review and the pilot study highlight the potential of pharmacogenetics in determining vulnerability to overdose of opioids.

Monitoring cocaine use and abstinence among cocaine users for contingency management interventions

During contingency management interventions, reinforcement of cocaine abstinence is arranged by delivering an incentive when a urine sample tests cocaine-negative. The use of qualitative versus quantitative urinalysis testing may have important implications for effects on cocaine abstinence. Qualitative testing (i.e., testing that solely identifies whether a particular substance is present or absent) may not detect short-term cocaine abstinence because a single instance of cocaine use can result in cocaine-positive urine over many days. Quantitative testing (i.e., testing that identifies how much of a substance is present) may be more sensitive to short-term cocaine abstinence; however, the selection of a criterion for distinguishing new use versus carryover from previous use is an important consideration. The present study examined benzoylecgonine concentrations, the primary metabolite of cocaine, in urine samples collected three times per week for 30 weeks from 28 cocaine users who were exposed to a cocaine abstinence contingency. Of the positive urine samples (benzoylecgonine concentration >300 ng/ml), 29%, 21%, 14%, and 5% of the samples decreased in benzoylecgonine concentration by more than 20%, 40%, 60%, and 80% per day, respectively. As the size of the decrease increased, the likelihood of that sample occurring during a period leading to a cocaine-negative urine sample (benzoylecgonine concentration ≤300 ng/ml) also increased. The number of days required to produce a cocaine-negative sample following a positive sample ranged from 1 to 10 days and was significantly correlated with the starting benzoylecgonine level (r = 0.43, p < 0.001). The present analyses may aid in the development of procedures that allow for the precise reinforcement of recent cocaine abstinence during contingency management interventions.

Precise simultaneous quantification of methadone and cocaine in rat serum and brain tissue samples following their successive i.p. administration

A sensitive high-performance liquid chromatography (HPLC) assay with dual UV detection has been developed and validated for the simultaneous quantification of methadone and cocaine in rat serum and brain tissue samples. Liquid-liquid extraction using hexanes was applied for samples extraction with Levo-Tetrahydropalmatine (L-THP) as the internal standard. Chromatographic separation of the analytes was achieved on a reversed-phase Waters Symmetry^® C₁₈ column (150mm×4.6mm, 5μm). A gradient elution was employed with a mobile phase consisting of 5mM potassium phosphate containing 0.1% triethylamine (pH=6.5) (A) and acetonitrile (B) with a flow rate of 1mL/min. UV detection was employed at 215nm and 235nm for the determination of methadone and cocaine, respectively. The calibration curves were linear over the range of 0.05-10μg/mL for both methadone and cocaine. The assay was validated according to FDA guidelines for bioanalytical method validation and results were satisfactory and met FDA criteria. Inter-day accuracy values of serum and brain samples ranged from 96.97 to 105.59% while intra-day accuracy values ranged from 91.49 to 111.92%. Stability assays showed that both methadone and cocaine were stable during sample storage, preparation, and analytical procedures. The method was successfully used to analyze biological samples obtained from a drug- drug interaction pharmacokinetics (PK) study conducted in rats to investigate the effect of methadone on cocaine PK. Our method not only can be used for bioanalysis of samples obtained from rats but also can potentially be applied to human biological serum samples to monitor compliance to methadone maintenance therapy (MMT) and to detect possible cocaine-methadone co-abuse.

Correlates of cocaine use during methadone treatment: implications for screening and clinical management (ANRS Methaville study)

Background

Cocaine use is frequent in patients receiving methadone maintenance treatment (MMT) and can jeopardize their treatment response. Identifying clinical predictors of cocaine use during methadone treatment can potentially improve clinical management. We used longitudinal data from the ANRS Methaville trial both to describe self-reported occasional and regular cocaine use during MMT and to identify clinical predictors.

Methods

We selected 183 patients who had data on cocaine (or crack) use at months 0 (M0), M6, and/or M12, accounting for 483 visits. The outcome was “cocaine use” in three categories: “no,” “occasional,” and “regular” use. To identify factors associated with the outcome over time, we performed a mixed multinomial logistic regression.

Results

Time on methadone was significantly associated with a decrease in occasional but not in regular cocaine use from 14.7 % at M0 to 7.1 % at M12, and from 10.7 % at baseline to 6.5 % at M12, respectively. After multiple adjustments, opiate injection, individuals screening positive for attention deficit hyperactivity disorder (ADHD) symptoms, and those presenting depressive symptoms were more likely to regularly use cocaine.

Conclusions

Although time on MMT had a positive impact on occasional cocaine use, it had no impact on regular cocaine use. Moreover, regular cocaine users were more likely to report opiate injection and to present ADHD and depressive symptoms. Early screening of these disorders and prompt tailored pharmacological and behavioral interventions can potentially reduce cocaine use and improve response to MMT.

Trial registration

The trial is registered with the French Agency of Pharmaceutical Products (AFSSAPS) under the number 2008-A0277-48, the European Union Drug Regulating Authorities Clinical Trials, number Eudract 2008-001338-28, the ClinicalTrials.gov Identifier: NCT00657397, and the International Standard Randomised Controlled Trial Number Register ISRCTN31125511.

Relationship between plasma concentrations of the l-enantiomer of methadone and response to methadone maintenance treatment

This study evaluated the relationship between the plasma concentration of l-methadone and response to methadone in real-world patients, in order to identify a minimum plasma concentration above which methadone treatment is effective. Ninety-four patients with opioid dependence under maintenance methadone treatment were consecutively recruited. Response was defined as negative urine analyses in the three weeks prior to the blood sampling. The percentage of participants with a plasma l-methadone concentration between 100 and 250 ng/ml was 54.2% among those with a methadone dosage ≥60 mg/day. Plasma l-methadone concentrations were significantly higher in patients with negative urine analyses compared with those with positive urine analyses (median 93 vs. 77 ng/ml, Mann-Whitney test, P<0.05). Above plasma l-methadone concentrations of 200 ng/ml no heroin use was reported and urine analyses were negative. Moreover, above concentrations of 250 ng/ml craving was absent. Examination of demographic correlates of treatment outcome indicated that older age, a stable job and being married were protective against the use of heroin. Mean plasma l-methadone concentration was significantly lower in patients who used cannabis compared with those who did not use cannabis, after adjusting for methadone dosage. In conclusion our results identify specific cut-offs for plasma l-methadone concentrations about which therapeutic response is observed and provide new evidence that therapeutic response is associated with patient׳s demographic characteristics. This underscores the need to monitor plasma methadone concentrations as part of Drug Addiction Services routine practice, in order to provide an objective framework for changing the methadone dosage.

The impact of recent cocaine use on plasma levels of methadone and buprenorphine in patients with and without HIV-infection

Cocaine decreases methadone and buprenorphine plasma concentrations. HIV infection and/or antiretroviral medication use may impact these relationships. We sought to determine the association between recent cocaine use and methadone and buprenorphine concentrations in HIV-infected and uninfected subjects in clinical care. R- and S-methadone or buprenorphine and norbuprenorphine concentrations were assessed at 0.5, 1, 2, and 24 hours after dosing in subjects with confirmed cocaine use and abstinence. We compared methadone and buprenorphine concentrations for cocaine use vs. abstinence, by HIV status in 16 subjects receiving methadone (6 HIV-infected) and 17 receiving buprenorphine (8 HIV-infected). With recent cocaine use, peak R-methadone (244 vs. 297 ng/mL, p = 0.03) and peak S-methadone (285 vs. 339 ng/mL); p = 0.03 concentrations were lower in HIV-uninfected subjects only. Peak buprenorphine and norbuprenorphine concentrations were unchanged regardless of cocaine use or HIV status. Cocaine may decrease methadone concentrations in HIV-uninfected subjects. HIV infection or its treatment may attenuate cocaine's effect on methadone.

Methadone: a review of drug-drug and pathophysiological interactions

Numerous established and potential drug interactions with methadone are clinically important in people treated with methadone either for addiction or for chronic pain. Methadone users often have comorbidities and are prescribed drugs that may interact with methadone. Methadone is extensively metabolized by cytochrome P450 (CYP) 3A4 and to a lesser extent by CYP 1A2, 2D6, 2D8, 2C9/2C8, 2C19, and 2B6. Eighty-six percent of methadone is protein bound, predominately to α1-acid glycoprotein (AGP). Polymorphisms in or interactions with CYPs that metabolize methadone, changes in protein binding, and other pathophysiological conditions affect the pharmacokinetic properties of methadone. It is critical for health care providers who treat patients on methadone to have adequate information on the interactions of methadone with other drugs of abuse and other medications. We set out to describe drug-drug interactions as well as physiological and pathophysiological factors that may impact the pharmacokinetics of methadone. Using MEDLINE, we conducted a systematic search for papers and related abstracts published between 1966 and June 2010. Keywords that included methadone, drug-drug interactions, CYP P450 and AGP identified a total of 7709 papers. Other databases, including the Cochrane Database of Systematic Reviews and Scopus, were also searched; an additional 929 papers were found. Final selection of 286 publications was based on the relevance of each paper to the topic. Over 50 such interactions were found. Interactions of methadone with other drugs can lead to increased or decreased methadone drug levels in patients and result in potential overdose or withdrawal, respectively. The former can contribute to methadone's fatality. Prescribers of methadone and pharmacists should enquire about any new medications (including natural products and over-the-counter medications) periodically, and especially when an otherwise stable patient suddenly experiences drug craving, withdrawal or intoxication.

The impact of cocaine use on outcomes in HIV-infected patients receiving buprenorphine/naloxone

BACKGROUND

Cocaine use is common in opioid-dependent HIV-infected patients, but its impact on treatment outcomes in these patients receiving buprenorphine/naloxone is not known.

METHODS

We conducted a prospective study in 299 patients receiving buprenorphine/naloxone who provided baseline cocaine data and a subset of 266 patients who remained in treatment for greater than or equal to one quarter. Assessments were conducted at baseline and quarterly for 1 year. We evaluated the association between baseline and in-treatment cocaine use on buprenorphine/naloxone retention, illicit opioid use, antiretroviral adherence, CD4 counts, HIV RNA, and risk behaviors.

RESULTS

Sixty-six percent (197 of 299) of patients reported baseline cocaine use and 65% (173 of 266) of patients with follow-up data reported in-treatment cocaine use. Baseline and in-treatment cocaine use did not impact buprenorphine/naloxone retention, antiretroviral adherence, CD4 lymphocytes, or HIV risk behaviors. However, baseline cocaine use was associated with a 14.8 (95% confidence interval [CI], 9.0-24.2) times greater likelihood of subsequent cocaine use (95% CI, 9.0-24.2), a 1.4 (95% CI, 1.02-2.00) times greater likelihood of subsequent opioid use, and higher log10 HIV RNA (P < 0.016) over time. In-treatment cocaine use was associated with a 1.4 (95% CI, 1.01-2.00) times greater likelihood of concurrent opioid use.

CONCLUSIONS

Given cocaine use negatively impacts opioid and HIV treatment outcomes, interventions to address cocaine use in HIV-infected patients receiving buprenorphine/naloxone treatment are warranted.

Drug interactions associated with methadone, buprenorphine, cocaine, and HIV medications: implications for pregnant women

Pregnancy in substance-abusing women with HIV/AIDS presents a complex clinical challenge. Opioid-dependent women need treatment with opioid therapy during pregnancy to protect the health of mother and developing fetus. However, opioid therapies, methadone and buprenorphine, may have drug interactions with some HIV medications that can have adverse effects leading to suboptimal clinical outcomes. Further, many opioid-dependent individuals have problems with other forms of substance abuse, for example, cocaine abuse, that could also contribute to poor clinical outcomes in a pregnant woman. Physiological changes, including increased plasma volume and increased hepatic and renal blood flow, occur in the pregnant woman as the pregnancy progresses and may alter medication needs with the potential to exacerbate drug interactions, although there is sparse literature on this issue. Knowledge of possible drug interactions between opioids, other abused substances such as cocaine, HIV therapeutics, and other frequently required medications such as antibiotics and anticonvulsants is important to assuring the best possible outcomes in the pregnant woman with opioid dependence and HIV/AIDS.

Drug interactions of clinical importance among the opioids, methadone and buprenorphine, and other frequently prescribed medications: a review

Drug interactions are a leading cause of morbidity and mortality. Methadone and buprenorphine are frequently prescribed for the treatment of opioid addiction. Patients needing treatment with these medications often have co-occurring medical and mental illnesses that require medication treatment. The abuse of illicit substances is also common in opioid-addicted individuals. These clinical realities place patients being treated with methadone and buprenorphine at risk for potentially toxic drug interactions. A substantial literature has accumulated on drug interactions between either methadone or buprenorphine with other medications when ingested concomitantly by humans. This review summarizes current literature in this area.