SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Morphine

170

BACKGROUND: Pre-eclampsia/eclampsia is one of the most common causes of maternal and perinatal morbidity and mortality in low and middle income countries. Magnesium sulfate is the drug of choice for prevention of seizures as part of comprehensive management of the disease. Despite the compelling evidence for the effectiveness of magnesium sulfate, concern has been expressed about its safety and potential for toxicity, particularly among providers in low- and middle-income countries. The purpose of this review was to determine whether the literature published in these global settings supports the concerns about the safety of use of magnesium sulfate. METHODS: An integrative review of the literature was conducted to document the known incidences of severe adverse reactions to magnesium sulphate, and specific outcomes of interest related to its use. All types of prospective clinical studies were included if magnesium sulfate was used to manage pre-eclampsia or eclampsia, the study was conducted in a low- or middle-income country, and the study included the recording of the incidence of any adverse side effect resulting from magnesium sulfate use. RESULTS: A total of 24 studies that compared a magnesium sulfate regimen against other drug regimens and examined side effects among 34 subject groups were included. The overall rate of absent patellar reflex among all 9556 aggregated women was 1.6%, with a range of 0-57%. The overall rate of respiratory depression in 25 subject groups in which this outcome was reported was 1.3%, with a range of 0–8.2%. Delay in repeat administration of magnesium sulfate occurred in 3.6% of cases, with a range of 0-65%. Calcium gluconate was administered at an overall rate of less than 0.2%. There was only one maternal death that was attributed by the study authors to the use of magnesium sulfate among the 9556 women in the 24 studies. CONCLUSION: Concerns about safety and toxicity from the use of magnesium sulfate should be mitigated by findings from this integrative review, which indicates a low incidence of the most severe side effects, documented in studies that used a wide variety of standard and modified drug regimens. Adverse effects of concern to providers occur infrequently, and when they occurred, a delay of repeat administration was generally sufficient to mitigate the effect. Early screening and diagnosis of the disease, appropriate treatment with proven drugs, and reasonable vigilance for women under treatment should be adopted as global policy and practice.

Concepts: Pharmacology, Effectiveness, Magnesium sulfate, Sulfur, Morphine, Adverse effect, Salt, Iatrogenesis

170

To aid public health policymaking, we studied the cost-effectiveness of buprenorphine, naltrexone, and placebo interventions for heroin dependence in Malaysia.

Concepts: Health economics, Morphine, Heroin, Naloxone, Drug rehabilitation

169

This issue of Molecular Pharmacology is dedicated to Dr. Avram Goldstein, the journal’s founding Editor and one of the leaders in the development of modern pharmacology. This chapter focuses on his contributions to the discovery of the dynorphins and evidence that members of this family of opioid peptides are endogenous agonists for the kappa opioid receptor. In his original publication describing the purification and sequencing of dynorphin A, Avram described this peptide as ‘extraordinarily potent’ (‘dyn’ from the Greek, dynamis = power and ‘-orphin’ for endogenous morphine peptide). The name originally referred to its high affinity and great potency in the bioassay that was used to follow its activity during purification, but the name has come to have a second meaning: Studies of its physiological function in brain continue to provide powerful insights to the molecular mechanisms controlling the mood disorders and drug addiction. In the 30 years since its discovery, we have learned that the dynorphin peptides are released in brain during stress exposure. Once released, they activate kappa opioid receptors distributed throughout the brain and spinal cord where they trigger cellular responses resulting in different stress responses: analgesia, dysphoria-like behaviors, anxiety-like responses, and increased addiction behaviors in experimental animals. Avram predicted that a detailed molecular analysis of opiate drug actions would someday lead to better treatments for drug addiction, and he would be gratified to know that subsequent studies enabled by his discovery of the dynorphins resulted in insights that hold great promise for new treatments for addiction and depressive disorders.

Concepts: Opioid, Morphine, Opioid receptor, Heroin, Buprenorphine, Endorphin, Codeine, Kappa Opioid receptor

167

It is well-known that genotypic differences can account for the subject-specific responses to opiate administration. In this regard, the basal activity of the endogenous system (either at the receptor or at the ligand level) can modulate the effects of exogenous agonists as morphine, and vice versa. The μ opioid receptor from zebrafish, dre-oprm1, binds endogenous peptides and morphine with similar affinities. Morphine administration during development altered the expression of the endogenous opioid propeptides proenkephalins and proopiomelanocortin. Treatment with opioid peptides (Met-ENK, MEGY and β-END) modulated dre-oprm1 expression during development. Knocking-down dre-oprm1 gene significantly modified the mRNA expression of the penk and pomc genes, thus indicating that oprm1 is involved in shaping penk and pomc expression. Besides, the absence of a functional oprm1 clearly disrupted the embryonic development, as proliferation was disorganized in the central nervous system of oprm1-morphant embryos: mitotic cells were found widespread through the optic tectum, and not restricted to the proliferative areas of the mid- and hindbrain. TUNEL staining revealed that the number of apoptotic cells in the Central Nervous System (CNS) of morphants was clearly increased at 24 hpf. These findings will help to understand the role of the endogenous opioid system in the CNS development. Our results will also contribute to unravel the complex feedback loops which modulate opioid activity, and which may be involved in establishing a coordinated expression of both receptors and endogenous ligands. Further knowledge of the complex interactions between the opioid system and analgesic drugs will provide insights that may be relevant for analgesic therapy.

Concepts: Central nervous system, Opioid, Morphine, Opioid receptor, Buprenorphine, Hydrocodone, Codeine, Oxycodone

167

CO(2)-laser C-fibre evoked cortical potentials (LCEPs) is a potentially useful animal model for studies of pain mechanisms. A potential confounding factor when assessing analgesic effects of systemically administered drugs using LCEP is sedation. This study aims to clarify: 1) the relation between level of anaesthesia and magnitude of LCEP, 2) the effects of a sedative and an analgesic on LCEP and dominant EEG frequency 3) the effects of a sedative and analgesic on LCEP when dominant EEG frequency is kept stable. LCEP and EEG were recorded in isoflurane/nitrous-oxide anaesthetized rats. Increasing isoflurane level gradually reduced LCEPs and lowered dominant EEG frequencies. Systemic midazolam (10 μmol/kg) profoundly reduced LCEP (19% of control) and lowered dominant EEG frequency. Similarly, morphine 1 and 3 mg/kg reduced LCEP (39%, 12% of control, respectively) and decreased EEG frequency. When keeping the dominant EEG frequency stable, midazolam caused no significant change of LCEP. Under these premises, morphine at 3 mg/kg, but not 1 mg/kg, caused a significant LCEP reduction (26% of control). In conclusion, the present data indicate that the sedative effects should be accounted for when assessing the analgesic effects of drug. Furthermore, it is suggested that LCEP, given that changes in EEG induced by sedation are compensated for, can provide information about the analgesic properties of systemically administrated drugs.

Concepts: Opioid, Pain, Somatosensory system, Nociception, Morphine, Analgesic, Codeine, Sedative

165

The benzylisoquinoline alkaloid papaverine, synthesized in low amount in most of the opium poppy varieties of Papaver somniferum, is used as a vasodilator muscle relaxant and antispasmodic. Papaverine biosynthesis remains controversial as two different routes utilizing either (S)-coclaurine or (S)-reticuline have been proposed with uncharacterized intermediate steps. In an attempt to elucidate papaverine biosynthesis and identify putative genes involved in uncharacterized steps, we carried out comparative transcriptome analysis of high papaverine mutant (pap1) and normal cultivar (BR086) of P. somniferum. This natural mutant synthesizes more than 12-fold papaverine in comparison to BR086. We established more than 238 Mb transcriptome data separately for pap1 and BR086. Assembly of reads generated 127,342 and 106,128 unigenes in pap1 and BR086, respectively. Digital gene expression analysis of transcriptomes revealed 3,336 differentially expressing unigenes. Enhanced expression of (S)-norcoclaurine-6-O-methyltransferase (6OMT), (S)-3'-hydroxy-N-methylcoclaurine 4'-O-methyltransferase (4'OMT), norreticuline 7-O-methyltransferase (N7OMT) and down-regulation of reticuline 7-O-methyltransferase (7OMT) in pap1 in comparison to BR086 suggest (S)-coclaurine as the route for papaverine biosynthesis. We also identified several methyltransferases and dehydrogenases with enhanced expression in pap1 in comparison to BR086. Our analysis using natural mutant, pap1, concludes that (S)-coclaurine is the branch-point intermediate and preferred route for papaverine biosynthesis. Differentially expressing methyltransferases and dehydrogenases identified in this study will help in elucidating complete biosynthetic pathway of papaverine. The information generated will be helpful in developing strategies for enhanced biosynthesis of papaverine through biotechnological approaches.

Concepts: Gene, Gene expression, Morphine, Opium, Opium poppy, Papaver, Papaverine, Poppy seed

164

Benzylisoquinoline alkaloids (BIAs) are a diverse group of biologically active specialized metabolites produced mainly in four plant families. BIA metabolism is likely of monophyletic origin and involves multiple enzymes yielding structurally diverse compounds. Several BIAs possess defensive properties against pathogenic microorganisms and herbivores. Opium poppy (Papaver somniferum: Papaveraceae) has emerged as a model system to investigate the cellular localization of BIA biosynthesis. Although alkaloids accumulate in the laticifer cytoplasm (latex) of opium poppy, corresponding biosynthetic enzymes and gene transcripts are localized to proximal sieve elements and companion cells, respectively. In contrast, BIA metabolism in the non-laticiferous meadow rue (Thalictrum flavum; Ranunculaceae) occurs independent of the phloem. Evidence points toward the adoption of diverse strategies for the biosynthesis and accumulation of alkaloids as defensive compounds. Recruitment of cell types involved in BIA metabolism, both within and external to the phloem, was likely driven by selection pressures unique to different taxa. The biochemistry, cell biology, ecophysiology, and evolution of BIA metabolism are considered in this context.

Concepts: Protein, Cell, Bacteria, Metabolism, Organism, Morphine, Opium, Opium poppy

161

Prescription opioid use is highly associated with risk of opioid-related death, with 1 of every 550 chronic opioid users dying within approximately 2.5 years of their first opioid prescription. Although gabapentin is widely perceived as safe, drug-induced respiratory depression has been described when gabapentin is used alone or in combination with other medications. Because gabapentin and opioids are both commonly prescribed for pain, the likelihood of co-prescription is high. However, no published studies have examined whether concomitant gabapentin therapy is associated with an increased risk of accidental opioid-related death in patients receiving opioids. The objective of this study was to investigate whether co-prescription of opioids and gabapentin is associated with an increased risk of accidental opioid-related mortality.

Concepts: Experimental design, Epidemiology, Death, Drug, Opioid, Morphine, Psychoactive drug, Recreational drug use

151

Pain places a devastating burden on patients and society and current pain therapeutics exhibit limitations in efficacy, unwanted side effects and the potential for drug abuse and diversion. Although genetic evidence has clearly demonstrated that the voltage-gated sodium channel, Nav1.7, is critical to pain sensation in mammals, pharmacological inhibitors of Nav1.7 have not yet fully recapitulated the dramatic analgesia observed in Nav1.7-null subjects. Using the tarantula venom-peptide ProTX-II as a scaffold, we engineered a library of over 1500 venom-derived peptides and identified JNJ63955918 as a potent, highly selective, closed-state Nav1.7 blocking peptide. Here we show that JNJ63955918 induces a pharmacological insensitivity to pain that closely recapitulates key features of the Nav1.7-null phenotype seen in mice and humans. Our findings demonstrate that a high degree of selectivity, coupled with a closed-state dependent mechanism of action is required for strong efficacy and indicate that peptides such as JNJ63955918 and other suitably optimized Nav1.7 inhibitors may represent viable non-opioid alternatives for the pharmacological treatment of severe pain.

Concepts: Pharmacology, Action potential, Pain, Enzyme inhibitor, Sodium, Agonist, Morphine, Erythromelalgia

151

QTc prolongation and Torsade de Ppointes have been reported in patients on methadone maintenance.

Concepts: QT interval, Morphine, Heroin, Methadone, Drug rehabilitation, Ibogaine