Identification and synthesis of norhydromorphone, and determination of antinociceptive activities in the rat formalin test

Fentanyl Analogs Exert Antinociceptive Effects via Sodium Channel Blockade in Mice

The formalin test is one approach to studying acute pain in rodents. Similar to formalin, injection with glutamate and veratrine can also produce a nociceptive response. This study investigated whether opioid-related compounds could suppress glutamate- and veratrine-induced nociceptive responses in mice at the same dose. The administration of morphine (3 mg/kg), hydromorphone (0.4 mg/kg), or fentanyl (0.03 mg/kg) suppressed glutamate-induced nociceptive response, but not veratrine-induced nociceptive response at the same doses. However, high doses of morphine (10 mg/kg), hydromorphone (2 mg/kg), or fentanyl (0.1 mg/kg) produced a significant reduction in the veratrine-induced nociceptive response. These results indicate that high doses are required when using morphine, hydromorphone, or fentanyl for sodium channel-related neuropathic pain, such as ectopic activity. As a result, concerns have arisen about overdose and abuse if the dose of opioids is steadily increased to relieve pain. In contrast, trimebutine (100 mg/kg) and fentanyl analog isobutyrylfentanyl (iBF; 0.1 mg/kg) suppressed both glutamate- and veratrine-induced nociceptive response. Furthermore, nor-isobutyrylfentanyl (nor-iBF; 1 mg/kg), which is a metabolite of iBF, suppressed veratrine-induced nociceptive response. Besides, the optimal antinociceptive dose of iBF, unlike fentanyl, only slightly increased locomotor activity and did not slow gastrointestinal transit. Cancer pain is a complex condition driven by inflammatory, neuropathic, and cancer-specific mechanisms. Thus, iBF may have the potential to be a superior analgesic than fentanyl.

Hydrocodone, Oxycodone, and Morphine Metabolism and Drug-Drug Interactions

Awareness of drug interactions involving opioids is critical for patient treatment as they are common therapeutics used in numerous care settings, including both chronic and disease-related pain. Not only do opioids have narrow therapeutic indexes and are extensively used, but they have the potential to cause severe toxicity. Opioids are the classical pain treatment for patients who suffer from moderate to severe pain. More importantly, opioids are often prescribed in combination with multiple other drugs, especially in patient populations who typically are prescribed a large drug regimen. This review focuses on the current knowledge of common opioid drug-drug interactions (DDIs), focusing specifically on hydrocodone, oxycodone, and morphine DDIs. The DDIs covered in this review include pharmacokinetic DDI arising from enzyme inhibition or induction, primarily due to inhibition of cytochrome p450 enzymes (CYPs). However, opioids such as morphine are metabolized by uridine-5'-diphosphoglucuronosyltransferases (UGTs), principally UGT2B7, and glucuronidation is another important pathway for opioid-drug interactions. This review also covers several pharmacodynamic DDI studies as well as the basics of CYP and UGT metabolism, including detailed opioid metabolism and the potential involvement of metabolizing enzyme gene variation in DDI. Based upon the current literature, further studies are needed to fully investigate and describe the DDI potential with opioids in pain and related disease settings to improve clinical outcomes for patients. SIGNIFICANCE STATEMENT: A review of the literature focusing on drug-drug interactions involving opioids is important because they can be toxic and potentially lethal, occurring through pharmacodynamic interactions as well as pharmacokinetic interactions occurring through inhibition or induction of drug metabolism.

Pharmacogenetic Analysis Enables Optimization of Pain Therapy: A Case Report of Ineffective Oxycodone Therapy

Patients suffering from chronic pain may respond differently to analgesic medications. For some, pain relief is insufficient, while others experience side effects. Although pharmacogenetic testing is rarely performed in the context of analgesics, response to opiates, non-opioid analgesics, and antidepressants for the treatment of neuropathic pain can be affected by genetic variants. We describe a female patient who suffered from a complex chronic pain syndrome due to a disc hernia. Due to insufficient response to oxycodone, fentanyl, and morphine in addition to non-steroidal anti-inflammatory drug (NSAID)-induced side effects reported in the past, we performed panel-based pharmacogenotyping and compiled a medication recommendation. The ineffectiveness of opiates could be explained by a combined effect of the decreased activity in cytochrome P450 2D6 (CYP2D6), an increased activity in CYP3A, and an impaired drug response at the µ-opioid receptor. Decreased activity for CYP2C9 led to a slowed metabolism of ibuprofen and thus increased the risk for gastrointestinal side effects. Based on these findings we recommended hydromorphone and paracetamol, of which the metabolism was not affected by genetic variants. Our case report illustrates that an in-depth medication review including pharmacogenetic analysis can be helpful for patients with complex pain syndrome. Our approach highlights how genetic information could be applied to analyze a patient's history of medication ineffectiveness or poor tolerability and help to find better treatment options.

Pharmacokinetics of hydromorphone hydrochloride after intravenous and intramuscular administration in guinea pigs (Cavia porcellus)

OBJECTIVE

To determine the pharmacokinetics of hydromorphone hydrochloride after IV and IM administration in guinea pigs (Cavia porcellus).

ANIMALS

8 healthy adult guinea pigs (4 sexually intact females and 4 sexually intact males).

PROCEDURES

In a crossover study, hydromorphone (0.3 mg/kg) was administered once IM (epaxial musculature) or IV (cephalic catheter) to each guinea pig at a 1-week interval (2 treatments/guinea pig). Blood samples were collected before and at predetermined intervals after drug administration via a vascular access port. Plasma hydromorphone concentrations were determined by liquid chromatography-tandem mass spectrometry. Noncompartmental analysis of data was used to calculate pharmacokinetic parameters.

RESULTS

Mean ± SD clearance and volume of distribution for hydromorphone administered IV were 52.8 ± 13.5 mL/min/kg and 2.39 ± 0.479 L/kg, respectively. Mean residence time determined for the IV and IM administration routes was 0.77 ± 0.14 hours and 0.99 ± 0.34 hours, respectively. The maximum observed plasma concentration following IM administration of hydromorphone was 171.9 ± 29.4 ng/mL. No sedative effects were observed after drug administration by either route.

CONCLUSIONS AND CLINICAL RELEVANCE

Pharmacokinetic data indicated that hydromorphone at a dose of 0.3 mg/kg may be administered IV every 2 to 3 hours or IM every 4 to 5 hours to maintain a target plasma concentration between 2 and 4 ng/mL in guinea pigs. Hydromorphone had high bioavailability after IM administration. Further research is necessary to evaluate the effects of other doses and administration routes and the analgesic effects of hydromorphone in guinea pigs.

Prescription Opioids. VI. Metabolism and Excretion of Hydromorphone in Urine Following Controlled Single-Dose Administration

Hydromorphone (HM), a prescription opioid and metabolite of morphine and hydrocodone, has been included in proposed revisions to the Mandatory Guidelines for Federal Workplace Drug Testing Programs. This study characterized the time course of HM in hydrolyzed and non-hydrolyzed urine specimens. Twelve healthy subjects were administered a single 8 mg controlled-release HM dose, followed by periodic collection of pooled urine specimens for 54 h following administration. Analysis of total and free HM was conducted by liquid chromatography tandem mass spectrometry at a 50 ng/mL limit of quantitation. Detection periods were determined over a range of thresholds from 50 to 2,000 ng/mL. HM was detected in 85.3% and 47.6% of hydrolyzed and non-hydrolyzed post-dose specimens, respectively. Initial detection of total HM was frequently observed in the first 4-6 h following dosing. The period of detection at the 50 ng/mL threshold averaged 52.3 h for total HM and 38.0 h for free HM. These data support that HM detection is optimized by using low thresholds (50-100 ng/mL) and including conjugated HM in the analysis.

A preliminary investigation into the practicality of use and duration of action of slow-release preparations of morphine and hydromorphone in laboratory rats

Significant advances have been made in our ability to assess pain and administer appropriate pain relief in laboratory animals. However, providing long-lasting analgesia using a route that does not involve animal restraint remains difficult. The objective of this study was to investigate whether oral administration of slow-release morphine or hydromorphone results in increased thermal nociception in laboratory rats. The results showed that 64 mg/kg morphine and 16 mg/kg hydromorphone induced comparable increases in foot withdrawal latencies for up to three hours postadministration; however, slow-release morphine increased response latencies for up to 11 hours. Whether these dose rates provide clinically effective pain relief has yet to be determined; however, these data suggest that using slow-release preparations could be an effective and highly practical method of elevating pain thresholds for a relatively prolonged period.

Capillary electrophoresis contributions to the hydromorphone metabolism in man

CE-ESI multistage IT-MS (CE-MS(n), n < or = 4) and computer simulation of fragmentation are demonstrated to be effective tools to detect and identify phase I and phase II metabolites of hydromorphone (HMOR) in human urine. Using the same CE conditions as previously developed for the analysis of urinary oxycodone and its metabolites, HMOR and its phase I metabolites produced by N-demethylation, 6-keto-reduction and N-oxidation and phase II conjugates of HMOR and its metabolites formed with glucuronic acid, glucose, and sulfuric acid could be detected in urine samples of a patient that were collected during a pharmacotherapy episode with daily ingestion of 48 mg of HMOR chloride. The CE-MS(n) data obtained with the HMOR standard, synthesized hydromorphol and hydromorphone-N-oxide, and CYP3A4 in vitro produced norhydromorphone were employed to identify the metabolites. This approach led to the identification of previously unknown HMOR metabolites, including HMOR-3O-glucide and various N-oxides, structures for which no standard compounds or mass spectra library data were available. Furthermore, the separation of alpha- and beta-hydromorphol, the stereoisomers of 6-keto-reduced HMOR, was achieved by CE in the presence of the single isomer heptakis(2,3-diacetyl-6-sulfato)-beta-CD. The obtained data indicate that the urinary excretion of alpha-hydromorphol is larger than that of beta-hydromorphol.

Endogenous opiates and behavior: 2004

This paper is the 27th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over 30 years of research. It summarizes papers published during 2004 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.