Development of an enantioselective high-performance liquid chromatography-tandem mass spectrometry method for the quantitative determination of methorphan and its O-demethylated metabolite in human blood and its application to post-mortem samples.

In the present work an isocratic enantioselective high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the separation and quantitative determination of dextro - and levo -methorphan and their pharmacologically relevant metabolites, dextrorphan and levorphanol, respectively, in human blood samples. The separation of enantiomers of methorphan and metabolites was performed on the polysaccharide-based chiral column Lux AMP in combination with acetonitrile and 5 mM aqueous ammonium bicarbonate pH 11 in the ratio 50:50 (%, v/v) as mobile phase with the flow rate 1 mL/min. The mass spectrometer was operated in scheduled multiple reaction monitoring (MRM) mode, with four transitions for each dextromethorpan, levomethorphan, dextrorphan and dextromethorphan-d3 and two transitions for each levorphanol, levorphanol-d3 and dextrorphan-d3. Application of this method to human post-mortem blood samples confirmed cases of severe overdosing with dextromethorphan, levomethorphan, and less commonly with both.

Levorphanol as a Second Line Opioid in Cancer Patients Presenting to an Outpatient Supportive Care Center: An Open-label Study.

CONTEXT: Levorphanol is a potent opioid agonist and NMDA receptor blocker with minimal drug interactions, and there are few reports of its use in cancer patients. OBJECTIVES: We aimed to determine the frequency of successful opioid rotation (OR) to levorphanol and the median opioid rotation ratio (ORR) from Morphine Equivalent Daily Dose (MEDD). METHODS: This is a prospective, single-group, interventional study. Cancer outpatients requiring an OR and receiving a MEDD of 60-300 mg were rotated to levorphanol using a ratio of 10:1 and assessed daily for 10-day. Successful OR was defined as a 2-point improvement in the Edmonton Symptom Assessment System (ESAS) pain score on day 10 or achieving the personalized pain goal between days 3-10 in patients with uncontrolled pain or resolution of opioid side effects (OSE) in those undergoing OR for OSE alone. The ORR to levorphanol was calculated using net-MEDD (MEDD before OR minus the MEDD of the breakthrough opioid used along with levorphanol after OR). RESULTS: Forty patients underwent OR to levorphanol, and uncontrolled pain 35/40 (87.5%) was the most common indication. The median net-MEDD and levorphanol doses were 95 and 10 mg, respectively, and 33/40 (82.5%) had a successful OR with a median (IQR) ORR of 8.56 (7.5-10). Successful OR was associated with significant improvement in ESAS and OSE scale scores. There was a strong association between MEDD and levorphanol dose. CONCLUSION: This study provided preliminary data that cancer patients could be successfully rotated to levorphanol using an ORR of 8.5. Levorphanol was associated with improved pain and symptom control and was well- tolerated.

A Comparison of Institutional Opioid Equianalgesia Tools: A National Study.

Context: Equianalgesic tools are commonly utilized to guide dose of analgesic therapy, but there is no national consensus on equianalgesic calculations in the United States. Objectives: To propose a summary of current opioid equianalgesic data that include variations and trends among national institutions. Methods: Opioid equianalgesic tools were obtained between May and September 2021. For meperidine, tramadol, codeine, hydrocodone, morphine, oxycodone, oxymorphone, hydromorphone, levorphanol, fentanyl, and tapentadol, details of adjustment for incomplete tolerance, opioid equianalgesic ratios, and formulation types were collected and analyzed. Baseline opioid pharmaco kinetic data were obtained through manufacturer labels on FDA databases, including half-life (T1/2), volume of distribution (Vd), clearance (Cl), area under the curve (AUC), max concentration (Cmax), and time to max concentration (Tmax). Results: Thirty-two institutions' equianalgesic tools were included with each study opioid appearing on an average of 23 institutions' tools. Few tools contained guidance on levorphanol or tapentadol; or included minimum and maximum recommended doses. All tools included guidance on fentanyl, hydromorphone, oxycodone, morphine, and hydrocodone. A minority of tools included guidance on cross-tolerance considerations (n = 12, 37.5%). Oral-tramadol-to-oral-morphine and oral-hydromorphone-to-intravenous (IV)-hydromorphone had the largest variances across equianalgesic tools (6.7 ± 2.8 and 4.06 ± 1.2 mg, respectively). Conclusion: Opioid equianalgesia tools from across the United States demonstrated significant variation in their inclusion of guidance on adjustment for incomplete cross-tolerance, oral-to-IV, and oral-to-oral opioid equianalgesic ratios, and which opioids and formulations were listed. Tramadol and hydromorphone had the most variation in their equianalgesic guidance among the opioids.

Tapentadol, Buprenorphine, and Levorphanol for the Treatment of Neuropathic Pain: a Systematic Review.

PURPOSE OF REVIEW: The objective of this systematic review is to present the available evidence for the utilization of the atypical opioids tapentadol, buprenorphine, and levorphanol for the treatment of neuropathic pain. RECENT FINDINGS: In total, 1619 articles were retrieved of which 10 studies were included. Of 5 included studies pertaining to tapentadol, 4 studies show tapentadol monotherapy to be effective for the treatment of diabetic peripheral neuropathy or chronic, radiating low back pain. Of the 3 studies included for buprenorphine, only one was a randomized controlled trial found not to have a statistically significant reduction in pain with TD buprenorphine likely due to very high withdrawal rates during the trial. Only 2 case reports were included from the available literature for levorphanol providing low-quality anecdotal evidence. The role of tapentadol, buprenorphine, and levorphanol for neuropathic pain conditions requires robust research including randomized controlled trials to evaluate their efficacy and safety.

Levorphanol versus methadone use: safety considerations.

Methadone has unique characteristics that make it an attractive agent for the treatment of chronic pain and opioid drug dependence. However, methadone prescription requires more clinical experience and close monitoring of patients to avoid its undesirable side effects. Recently, levorphanol has emerged as "a forgotten opioid" with a similar profile as methadone. Levorphanol has no impact on QTc prolongation and considerably less drug-drug interactions as compared to methadone. Lack of commercial availability, providers' unfamiliarity, and limited clinical data on its effectiveness remain practical issues. The objective of this article is to review and compare the safety considerations for methadone and levorphanol use.

Evolution of Analgesic Tolerance and Opioid-Induced Hyperalgesia Over 6 Months: Double-Blind Randomized Trial Incorporating Experimental Pain Models.

Contributors to the ongoing epidemic of prescription opioid abuse, addiction, and death include opioid tolerance, withdrawal symptoms, and possibly opioid-induced hyperalgesia (OIH). Thirty stable chronic nonmalignant pain patients entered a 6-month long, randomized, double-blind, dose-response, 2-center trial of the potent opioid levorphanol, conducted over a decade ago during an era of permissive opioid prescribing. Eleven were taking no opioids at study entry and eleven were taking between 35 and 122 morphine equivalents. Five weeks titration preceded twenty weeks stable dosing. Tolerance and OIH were inferred individually based on chronic pain ratings, brief pain inventory scores, and results of the brief thermal sensitization model at 5 opioid dosing sessions. Seventeen patients completed. The average final daily opioid dose was 132; range 14 to 300; average addition 105 morphine equivalents. After observed dosing, the brief thermal sensitization area of hyperalgesia changed minimally but the painfulness of skin heating was reduced. Weekly 0 to 100 visual analog scale pain ratings (average 64 at study entry, 48 at end titration, 45 at end stable dosing) decreased a median 19%, but 8 completed with higher visual analog scale ratings. Three completers had evidence of both tolerance and hyperalgesia. A fully-powered trial similar to this feasibility study is ethically questionable. A large-scale pragmatic trial is more realistic. TRIAL REGISTRATION: NCT00275249 Evolution of Analgesic Tolerance With Opioids PERSPECTIVE: A double-blind, 6-month, high-dose opioid feasibility trial, completed years ago, provides critically important data for clinically defining analgesic tolerance and OIH. Overall benefit was small, and 18% of patients had evidence of both tolerance and OIH. Future work requires a different approach than a classic randomized controlled trial design.

Pharmacological Characterization of Levorphanol, a G-Protein Biased Opioid Analgesic.

BACKGROUND: Levorphanol is a potent analgesic that has been used for decades. Most commonly used for acute and cancer pain, it also is effective against neuropathic pain. The recent appreciation of the importance of functional bias and the uncovering of multiple µ opioid receptor splice variants may help explain the variability of patient responses to different opioid drugs. METHODS: Here, we evaluate levorphanol in a variety of traditional in vitro receptor binding and functional assays. In vivo analgesia studies using the radiant heat tail flick assay explored the receptor selectivity of the responses through the use of knockout (KO) mice, selective antagonists, and viral rescue approaches. RESULTS: Receptor binding studies revealed high levorphanol affinity for all the µ, δ, and κ opioid receptors. In S-GTPγS binding assays, it was a full agonist at most µ receptor subtypes, with the exception of MOR-1O, but displayed little activity in ß-arrestin2 recruitment assays, indicating a preference for G-protein transduction mechanisms. A KO mouse and selective antagonists confirmed that levorphanol analgesia was mediated through classical µ receptors, but there was a contribution from 6 transmembrane targets, as illustrated by a lower response in an exon 11 KO mouse and its rescue with a virally transfected 6 transmembrane receptor splice variant. Compared to morphine, levorphanol had less respiratory depression at equianalgesic doses. CONCLUSIONS: While levorphanol shares many of the same properties as the classic opioid morphine, it displays subtle differences that may prove helpful in its clinical use. Its G-protein signaling bias is consistent with its diminished respiratory depression, while its incomplete cross tolerance with morphine suggests it may prove valuable clinically with opioid rotation.

Identifying Levorphanol Ingestion Using Urine Biomarkers in Health Care Patients.

BACKGROUND: Levorphanol is a long-acting opioid analgesic that is an optical isomer of dextrorphan, a metabolite of the over-the-counter cough suppressant dextromethorphan. Providers prescribing levorphanol for pain management may need to assess compliance through urine drug testing, as this agent is subject to abuse. Therefore, it is important to differentiate between dextromethorphan and levorphanol ingestion. OBJECTIVES: This article is the first to report urine concentrations of levorphanol/dextrorphan and 3-hydroxymorphinan in human urine and assesses the need for an enantiomeric analysis to distinguish between dextromethorphan and levorphanol ingestion. STUDY DESIGN: Retrospective data review. METHODS: Medication compliance test results were reviewed for 521 urine samples submitted to Aegis Sciences Corporation between July 2014 and July 2016. Samples were included in this analysis if dextromethorphan or levorphanol testing was requested by the ordering provider. Urine samples were hydrolyzed with beta-glucuronidase and analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). An enantiomeric analysis to distinguish levorphanol from dextrorphan and (-)-3-hydroxymorphinan (norlevorphanol) from (+)-3-hydroxymorphinan was not performed. RESULTS: Nineteen urine samples with levorphanol listed as prescribed had median levorphanol/dextrorphan and 3-hydroxymorphinan concentrations of 1,881 ng/mL and 141 ng/mL, respectively. One-quarter of the urine samples with dextromethorphan listed as prescribed did not have any detectable dextromethorphan or 3-methoxymorphinan. LIMITATIONS: An enantiomeric analysis was not utilized with the LC-MS/MS testing method; therefore, levorphanol could not be differentiated from dextrorphan, and (-)-3-hydroxymorphinan could not be differentiated from (+)-3-hydroxymorphinan. The hepatic and renal function for these patients was unknown; however, both could impact the metabolism, distribution, and excretion of levorphanol biomarkers in urine. The dextromethorphan and/or levorphanol dose and timing of last ingestion was also not assessed. CONCLUSIONS: It may be impossible to distinguish between levorphanol and dextromethorphan ingestion based on urine biomarkers, unless dextromethorphan or 3-methoxymorphinan is present or an enantiomeric analysis is performed. Therefore, the potential exists for patients prescribed levorphanol to ingest dextromethorphan and appear compliant with levorphanol therapy. This should prompt clinicians to consider the parameters of their laboratory's testing method when interpreting levorphanol drug test results. KEY WORDS: Levorphanol, dextrorphan, dextromethorphan, 3-hydroxymorphinan, urine testing, urine concentration, drug testing, medication compliance testing.

Levorphanol for Treatment of Intractable Neuropathic Pain in Cancer Patients.

Neuropathic pain in cancer patients is often difficult to treat, requiring a combination of several different pharmacological therapies. We describe two patients with complex neuropathic pain syndromes in the form of phantom limb pain and Brown-Sequard syndrome who did not respond to conventional treatments but responded dramatically to the addition of levorphanol. Levorphanol is a synthetic strong opioid that is a potent N-methyl-d-aspartate receptor antagonist, mu, kappa, and delta opioid receptor agonist, and reuptake inhibitor of serotonin and norepinephrine. It bypasses hepatic first-pass metabolism and thereby not subjected to numerous drug interactions. Levorphanol's unique profile makes it a potentially attractive opioid in cancer pain management.

Levorphanol use: past, present and future.

Levorphanol is a potent opioid analgesic that was first approved for use in the United States in 1953. Levorphanol is approved for use in moderate to severe pain where an opioid analgesic is appropriate. Levorphanol has a wide range of activities including mu opioid agonism, delta agonism, kappa1 and kappa3 receptor agonism, N-methyl-d-aspartate receptor antagonism and reuptake inhibition of both norepinephrine and serotonin. This multimodal profile might prove effective for pain syndromes that are refractory to other opioid analgesics, such as central and neuropathic pain and opioid-induced hyperalgesia. Levorphanol is well suited as a first-line opioid and can also be used during opioid rotation. It has no known effect on the cardiac QT interval or drug-drug interactions involving hepatic cytochrome P450s enzymes. In these regards, levorphanol may offer a superior safety profile over methadone and other long-acting opioids. Despite its prospective value of multiple mechanisms of action and the potential for treating various types of pain, levorphanol use has been largely supplanted by other recently approved opioids. Its waning use over the years has caused it to be referred to as the "Forgotten Opioid" and resulted in what some consider its underutilization. In fact, levorphanol is relatively unfamiliar to most prescribers. The purpose of this review is to inform practitioners about the attributes of this opioid and reintroduce it to clinicians as an option for treating moderate to severe pain when alternative treatment options are inadequate, not indicated or contraindicated.

Is levorphanol a better option than methadone?

BACKGROUND: Methadone has been a stalwart pharmacologic option for the management of opioid drug dependence for many years. It substitutes for opioid agonists and possesses certain pharmacokinetic properties that confer characteristics preferable to those of other opioids for this application. Methadone is likewise used as an option for the treatment of pain, particularly chronic pain. It has a spectrum of pharmacodynamic activity, including contributions from non-opioid components, that translates to its specific clinical attributes as an analgesic. Unfortunately, basic science studies and accumulated clinical experience with methadone have revealed some undesirable, and even worrisome, features, including issues of safety. The benefit/risk ratio of methadone might be acceptable if there was no better alternative, but neither its pharmacokinetic nor pharmacodynamic properties are unique to methadone. OBJECTIVE: We review the basic and clinical pharmacology of methadone and suggest that levorphanol should receive attention as a possible alternative. CONCLUSION: Unlike methadone, levorphanol is a more potent NMDA antagonist, possesses a higher affinity for DOR and KOR, has a shorter plasma half-life yet longer duration of action, has no CYP450 interactions or QTc prolongation risk, can be a viable option in the elderly, palliative care, and SCI patients, requires little to no need for co-administration of adjuvant analgesics, and has potentially a lower risk of drug-related Emergency Department visits compared to other opioids.

Synthesis and opioid activity of novel 6-ketolevorphanol derivatives.

Novel 6-ketolevorphanol analogs with diverse substitution patterns at ring C were synthesized and their binding affinities at the µ,δ and κ opioid receptors were investigated. The in vitro activity of the new analogs was then evaluated in the functional assay based on the electrically-stimulated contractions of the mouse ileum. It was shown that analogs with Δ7,8 bond had no significant potency at any of the opioid receptor types. In contrast, analogs with the saturated ring C were either potent κ agonist or antagonist depending on the absence or presence of the hydroxyl group in position 14.

Buprenorphine and opioid antagonism, tolerance, and naltrexone-precipitated withdrawal.

The dual antagonist effects of the mixed-action µ-opioid partial agonist/κ-opioid antagonist buprenorphine have not been previously compared in behavioral studies, and it is unknown whether they are comparably modified by chronic exposure. To address this question, the dose-related effects of levorphanol, trans-(-)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl] benzeneacetamide (U50,488), heroin, and naltrexone on food-maintained behavior in rhesus monkeys were studied after acute and chronic treatment with buprenorphine (0.3 mg/kg/day). In acute studies, the effects of levorphanol and U50,488 were determined at differing times after buprenorphine (0.003-10.0 mg/kg i.m.). Results show that buprenorphine produced similar, dose-dependent rightward shifts of the levorphanol and U50,488 dose-response curves that persisted for ≥ 24 h after doses larger than 0.1 mg/kg buprenorphine. During chronic treatment with buprenorphine, the effects of levorphanol, U50,488, heroin, and naltrexone were similarly determined at differing times (10 min to 48 h) after intramuscular injection. Overall, results show that buprenorphine produced comparable 3- to 10-fold rightward shifts in the U50,488 dose-response curve under both acute and chronic conditions, but that chronic buprenorphine produced larger (10- to ≥ 30-fold) rightward shifts in the heroin dose-effect function than observed acutely. Naltrexone decreased operant responding in buprenorphine-treated monkeys, and the position of the naltrexone dose-effect curve shifted increasingly to the left as the time after daily buprenorphine treatment increased from 10 min to 48 h. These results suggest that the µ-antagonist, but not the κ-antagonist, effects of buprenorphine are augmented during chronic treatment. In addition, the leftward shift of the naltrexone dose-effect function suggests that daily administration of 0.3 mg/kg buprenorphine is adequate to produce opioid dependence.

Exploration of catalytic properties of CYP2D6 and CYP3A4 through metabolic studies of levorphanol and levallorphan.

CYP2D6 and CYP3A4, two members of the cytochrome P450 superfamily of monooxygenases, mediate the biotransformation of a variety of xenobiotics. The two enzymes differ in substrate specificity and size and characteristics of the active site cavity. The aim of this study was to determine whether the catalytic properties of these isoforms, reflected by the differences observed from crystal structures and homology models, could be confirmed with experimental data. Detailed metabolite identification, reversible inhibition, and time-dependent inhibition were examined for levorphanol and levallorphan with CYP2D6 and CYP3A4. The studies were designed to provide a comparison of the orientations of substrates, the catalytic sites of the two enzymes, and the subsequent outcomes on metabolism and inhibition. The metabolite identification revealed that CYP3A4 catalyzed the formation of a variety of metabolites as a result of presenting different parts of the substrates to the heme. CYP2D6 was a poorer catalyst that led to a more limited number of metabolites that were interpreted in terms to two orientations of the substrates. The inhibition studies showed evidence for strong reversible inhibition of CYP2D6 but not for CYP3A4. Levallorphan acted as a time-dependent inhibitor on CYP3A4, indicating a productive binding mode with this enzyme not observed with CYP2D6 that presumably resulted from close interactions of the N-allyl moiety oriented toward the heme. All the results are in agreement with the large and flexible active site of CYP3A4 and the more restricted active site of CYP2D6.

Synthesis and pharmacological evaluation of 6,7-indolo/thiazolo-morphinans--further SAR of levorphanol.

To further extend the structure-activity relationships of levorphanol, two series of novel morphinans were prepared by incorporation of an indole or aminothiazole fragment to the hexyl ring (ring C) in levorphanol. Such morphinans differed from previously reported ligands in that such indole- or aminothiazole-containing morphinans displayed enhanced binding affinity to the delta opioid receptor, while the affinity to kappa and micro receptors was slightly reduced.

Can levorphanol be used like methadone for intractable refractory pain?

BACKGROUND: Levorphanol has been reported to provide analgesia at doses that suggest it does not act like other pure agonist opioids. A dual effect of action on both opioid receptors and n-methyl, d-aspartate (NMDA) receptors has been proposed to be responsible for this effect. METHOD: Case series of patients treated with levorphanol when pain did not respond adequately to other opioids, including methadone. RESULTS: During a 5-year period in a single palliative medicine practice, 20 of 244 patients with chronic nonmalignant pain in a palliative care clinic and 11 of 1508 terminally ill patients enrolled in hospice care whose severe chronic pain was not relieved by treatment with other opioids were treated with oral levorphanol. Of those 31 patients, 16 (52%) reported excellent relief of pain and 7 (22%) reported fair relief for a total response rate of 74%. DISCUSSION: These results suggest that levorphanol has a role in the treatment of pain syndromes that are refractory to other opioids. The pattern of relief seen in this case series is similar to that reported for methadone. Could it be that levorphanol may have a role like methadone for pain that is poorly controlled with other pure agonist opioids? We summarize what is known about levorphanol and provide a table for converting other opioids to levorphanol that was used for this case series.