Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.3.44 (P-glycoprotein)
 13,344 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Patient-controlled analgesia (PCA) has become standard procedure in the clinical treatment of pain. Its widespread use in patients with all kinds of diseases opens a variety of possible interactions between analgesics used for PCA and other drugs that might be administered concomitantly to the patient. Many of these drug interactions are of little clinical importance. However, some drug interactions have been reported to result in serious clinical problems. Drug interactions can either predominantly affect the pharmacokinetics or pharmacodynamics of the drug. Most important pharmacokinetic drug interactions occur at the level of drug metabolism or protein binding. Acceleration of methadone metabolism caused by cytochrome P450 (CYP) 3A4 induction by antiretroviral drugs or rifampicin (rifampin) has caused methadone withdrawal symptoms. Lack of morphine formation from codeine as a result of CYP2D6 inhibition by quinidine results in an almost complete loss of the analgesic effects of codeine. Alterations of methadone protein binding caused by an inhibition of alpha1-acid glycoprotein synthesis by alkylating substances are another possibility for predominantly pharmacokinetically based drug interactions during PCA. Furthermore, inhibition of P-glycoprotein by anticancer drugs could result in altered transmembrane transport of morphine, methadone or fentanyl, although this has not been shown to be of clinical relevance. Synergistic effects of systemically administered opioids with spinally or topically delivered opioids or anaesthetics have been reported frequently. The same is true for the opioid-sparing effects of coadministered non-opioid analgesics. Antidepressants, anticonvulsants or alpha2-adrenoreceptor agonists have also been shown to exert additive analgesic effects when administered together with an opioid. Inconsistent findings, however, are reported regarding the treatment of patients with opioid-induced nausea and sedation, since coadministration of antiemetics either increased or decreased the respective adverse effects or revealed additional unwanted drug effects.
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PMID:Drug interactions with patient-controlled analgesia. 1182 96

There are pharmacological differences between women and men that have important clinical consequences. For several drugs, there is a higher incidence in women of drug-induced QT prolongation and a potentially fatal arrhythmia, torsades de pointes. This may be a reflection of the longer baseline QT interval in women. A difference in cardiovascular disease between women and men is that women have a higher mortality rate after myocardial infarction (MI). Women also have a higher rate of hemorrhagic stroke after receiving thrombolytic therapy for an MI. Differences in effectiveness of analgesics have been demonstrated, with kappa opioids providing pain relief for women but not men. Drugs may have different pharmacokinetics in women and men because of differences in phase I and phase II enzymes that metabolize drugs. Conflicting results about biological sex differences have been reported for the major drug metabolizing enzyme, cytochrome P450 3A4 (3A4) and may be related to a role for P-glycoprotein, a cell membrane transporter, reported as two times higher in male livers than those of females. It has been reported that boys need a higher dose of 6-mercaptopurine, which is metabolized by thiopurine methyltransferase (TPMT). TPMT is reported to be 14% higher in male human liver biopsies than those from females. Verapamil, a drug for angina and hypertension, has different clearance and side effects in men and women. Ethnic/racial variations have also been demonstrated with the drug metabolizing enzymes, CYP2C9, 2C19, and 2D6.
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PMID:Biologic and molecular mechanisms for sex differences in pharmacokinetics, pharmacodynamics, and pharmacogenetics: Part I. 1239 93

The efflux transporter P-glycoprotein (P-gp) is an important component of the blood-brain barrier (BBB) that limits accumulation of many compounds in brain. Some opioids have been shown to interact with P-gp in vitro and in vivo. Genetic or chemical disruption of P-gp has been shown to enhance the antinociceptive and/or toxic effects of some opioids, although the extent of this phenomenon has yet to be understood. The purpose of this study was to assess quantitatively the influence of mdr1a P-gp on initial brain uptake of chemically diverse opioids in mice. The brain uptake of opioids selective for the mu (fentanyl, loperamide, meperidine, methadone, and morphine), delta (deltorphin II, DPDPE, naltrindole, SNC 121) and kappa (bremazocine and U-69593) receptor subtypes was determined in P-gp-competent (wild-type) and P-gp-deficient [mdr1a(-/-)] mice with an in situ brain perfusion model. BBB permeability of the opioids varied by several orders of magnitude in both mouse strains. The difference in brain uptake between P-gp-competent and P-gp-deficient mice ranged from no detectable effect (meperidine) to >/=8-fold increase in uptake (DPDPE, loperamide, and SNC 121). In addition, loperamide efflux at the BBB was inhibited by quinidine. These results demonstrate that P-gp modulation of opioid brain uptake varies substantially within this class of compounds, regardless of receptor subtype. P-gp-mediated efflux of opioids at the BBB may influence the onset, magnitude, and duration of analgesic response. The variable influence of P-gp on opioid brain distribution may be an important issue in the context of pharmacologic pain control and drug interactions.
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PMID:Variable modulation of opioid brain uptake by P-glycoprotein in mice. 1469 39

Endomorphin-1 (EM-1) and endomorphin-2 (EM-2) are two highly selective mu-opiate receptor agonists. We recently demonstrated that EM-1 and EM-2 have a saturable transport system from brain-to-blood in vivo. Since the endothelial cells are the main component of the non-fenestrated microvessels of the blood-brain barrier (BBB), we examined whether these endogenous tetrapeptides have a saturable transport system in cultured cerebral endothelial cells. EM-1 and EM-2 binding and transport were studied in a transwell system in which primary mouse endothelial cells were co-cultured with rat glioma cells. We found that binding of both endomorphins was greater on the basolateral than the apical cell surface. Flux of EM-1 and EM-2 occurred predominantly in the basolateral to apical direction, each showing self-inhibition with an excess of the respective endomorphin. Transport was not influenced by the addition of the P-glycoprotein inhibitor, cyclosporin A. Neither the mu-opiate receptor agonist DAMGO nor the delta-opiate receptor agonist DPDPE had any effect on the transport. Thus, the results show that a saturable transport system for EM-1 and EM-2 occurs at the level of endothelial cells of the BBB, and unlike beta-endorphin and morphine, P-glycoprotein is not needed for the brain-to-blood transport. Cross-inhibition of the transport of each endomorphin by the other suggests a shared transport system that is different from mu- or delta-opiate receptors. As endormorphins are mainly produced in the CNS, the presence of the efflux system at the BBB could play an important role in pain modulation and neuroendocrine control.
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PMID:Endomorphins exit the brain by a saturable efflux system at the basolateral surface of cerebral endothelial cells. 1534 52

This review uses a candidate gene approach to identify possible pharmacogenetic modulators of opioid therapy, and discusses these modulators together with demonstrated genetic causes for the variability in clinical effects of opioids. Genetically caused inactivity of cytochrome P450 (CYP) 2D6 renders codeine ineffective (lack of morphine formation), slightly decreases the efficacy of tramadol (lack of formation of the active O-desmethyl-tramadol) and slightly decreases the clearance of methadone. MDR1 mutations often demonstrate pharmacogenetic consequences, and since opioids are among the P-glycoprotein substrates, opioid pharmacology may be affected by MDR1 mutations. The single nucleotide polymorphism A118G of the mu opioid receptor gene has been associated with decreased potency of morphine and morphine-6-glucuronide, and with decreased analgesic effects and higher alfentanil dose demands in carriers of the mutated G118 allele. Genetic causes may also trigger or modify drug interactions, which in turn can alter the clinical response to opioid therapy. For example, by inhibiting CYP2D6, paroxetine increases the steady-state plasma concentrations of (R)-methadone in extensive but not in poor metabolisers of debrisoquine/sparteine. So far, the clinical consequences of the pharmacogenetics of opioids are limited to codeine, which should not be administered to poor metabolisers of debrisoquine/sparteine. Genetically precipitated drug interactions might render a standard opioid dose toxic and should, therefore, be taken into consideration. Mutations affecting opioid receptors and pain perception/processing are of interest for the study of opioid actions, but with modern practice of on-demand administration of opioids their utility may be limited to explaining why some patients need higher opioid doses; however, the adverse effects profile may be modified by these mutations. Nonetheless, at a limited level, pharmacogenetics can be expected to facilitate individualised opioid therapy.
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PMID:Genetic predictors of the clinical response to opioid analgesics: clinical utility and future perspectives. 1553 Jan 29

Myopathy is usually a non-fatal muscle disease involving skeletal muscle weakness, tenderness and pain with the possibility of the plasma creatinine kinase elevation. There are many different types of myopathies, some of which are genetic, inflammatory, or related to endocrine dysfunction. Also, numerous drugs have been reported to possess myotoxic effect. Myopathy is included among the potential side-effects and toxicities associated with the lipid lowering agents, particularly 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors. However, the precise mechanism of statin-induced muscle toxicity remains unclear. The muscle-related side-effects reported with lipid-lowering drugs are significant but quite rare (0.1%), when used in monotherapy; while the incidence of steroid-induced myopathy has varied from 7 to 60%% and chronic alcoholic myopathy seems to be common complication of alcoholism affecting approximately 50% of patients, respectively. This review focuses on the differential pathophysiological grounds of these muscular injuries induced by statins, fibrates, as well as some other agents: corticosteroids or alcohol. A wide spectrum of possible mechanisms and hypotheses including muscle enzyme defects, changes in mitochondrial function and intracellular metabolism, the influence on the cell membrane stability and drug interactions involving P-glycoprotein or cytochrome P 450 system have been presented.
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PMID:Drug-induced myopathies. An overview of the possible mechanisms. 1584 74

Vincristine (VCT) is a neurotoxic agent and also a substrate of multidrug resistance (MDR) transporters such as P-glycoprotein (P-gp) and MDR-associated proteins 1 and 2 (MRP1 and MRP2). These proteins are expressed in the central and peripheral nervous systems (CNS and PNS) and normally protect these structures against the harmful effects of VCT. The aim of this study was to elucidate the paradoxical relation between the MDR transporters and the VCT neurotoxicity. With a validated rat model of VCT-induced neuropathy, (1) the expressions of mdr1a (P-gp), mdr1b (P-gp), mrp1 (MRP1), and mrp2 (MRP2) genes were assessed by quantitative real-time polymerase chain reaction, and (2) the transporter activity was monitored using a radioactive tracer, (99m)Tc-sestamibi, in the CNS and PNS. The results showed higher expression of mdr1a and mdr1b genes (x3 and x35, respectively) in the brain than in the spinal ganglia in both control and treated animals. Transporter activity was higher (x10) in the CNS than in the PNS. Hence, P-gp protection may be lower in the PNS than in the CNS, and this may be responsible for the peripheral neurotoxicity of P-gp substrates. VCT treatment increased expression of the mdr1a gene in the CNS and PNS (both x1.7), mrp1 gene in the PNS (x1.7), and transporter activity in both the CNS and the PNS (x4 and x8, respectively). This transporter induction may induce adverse effects when analgesic drugs are administered to treat neuropathic pain.
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PMID:Patterns of P-glycoprotein activity in the nervous system during vincristine-induced neuropathy in rats. 1622 Dec 89

It has recently been suggested that P-glycoprotein is involved in the genesis and the treatment of the neurotoxic adverse events of anticancer drugs, including vincristine. A lower activity of P-glycoprotein in the peripheral nervous system (PNS) than in the central nervous system could contribute to the neurotoxicity of vincristine. Vincristine treatment is responsible for the induction of multidrug resistance (MDR) gene expression and transporter activity, with deleterious consequences, including a potential decrease in the efficiency of opioid analgesics, antidepressants or antiepileptics. Concerning cisplatin, which is also a strong neurotoxic drug but only an multidrug resistance protein 2 (MRP2) substrate, the same assumption could be suggested for MRP2 nervous function. The aim of this study was to assess MDR gene and protein activity in a rat model of cisplatin-induced neuropathy compared with different peripheral nerve injury models, i.e. mononeuropathy and inflammatory pain (monoarthritis). First, in cisplatin-induced neuropathy, this study demonstrated low MRP2 gene expression in dorsal root ganglia compared with the brain and spinal cord, which could contribute to the strong neurotoxicity of cisplatin in the PNS and particularly the dorsal root ganglia. Thus, gene expression increased in cisplatin-induced neuropathy but decreased in mononeuropathy and remained unchanged in monoarthritis models. Transporter activity of nervous tissues increased in the cisplatin-induced neuropathy, mononeuropathy and monoarthritis to different intensities (3.7-, 1.8- and 1.8-fold, respectively). The development of a MDR in the cisplatin-induced neuropathy is a striking difference with mononeuropathy and monoarthritis models, and characterizes the neuropathies induced by this anticancer drug.
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PMID:Involvement of the multidrug resistance transporters in cisplatin-induced neuropathy in rats. Comparison with the chronic constriction injury model and monoarthritic rats. 1685 77

Ondansetron is a potent antiemetic drug that acts through inhibition of the 5HT3 receptors for serotonin. Minimum alveolar concentration (MAC) for isoflurane is not affected by systemic ondansetron; however ondansetron is a substrate of P-glycoprotein, a transport pump expressed in the blood-brain barrier. Thus, we hypothesized that central nervous system concentrations of ondansetron might be reduced by the P-gp protein. As potent inhibitors of P-gp are in clinical trials to improve access of desirable chemotherapeutic and antibiotic drugs to the central nervous system, we studied the effect of ondansetron in the absence of extrusion by P-gp. Normal rats were given lumbar intrathecal ondansetron or vehicle. P-gp knockout mice and wild-type controls were treated with systemic ondansetron in the presence and absence of clinically used P-gp inhibitors. Nociception was assessed as thermal hindpaw withdrawal latency and immobility was assessed as isoflurane MAC. In rats, intrathecal ondansetron (20 g) increased thermal pain sensitivity by 20.0% +/- 5.8% (P < 0.01). Systemic ondansetron (2 mg/kg) increased pain sensitivity in P-gp knockout mice but had no effect in wild-type mice (P < 0.01). Systemic ondansetron had a small but statistically significant pronociceptive effect after treatment of wild-type mice with the P-gp inhibitor quinidine but not with cyclosporine or verapamil. Isoflurane MAC was not changed by intrathecal ondansetron in rats or systemically administered ondansetron in P-gp knockout mice. Intrathecal ondansetron can enhance thermal pain sensitivity. In the absence of P-gp protein, ondansetron can reach concentrations sufficient to increase pain sensitivity. Even with direct spinal application, ondansetron does not alter isoflurane MAC, supporting the idea that 5HT3 modulation does not play a role in general anesthetic immobility.
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PMID:The pronociceptive effect of ondansetron in the setting of P-glycoprotein inhibition. 1693 90

A series of biphenylaminocyclopropane carboxamide based bradykinin B1 receptor antagonists has been developed that possesses good pharmacokinetic properties and is CNS penetrant. Discovery that the replacement of the trifluoropropionamide in the lead structure with polyhaloacetamides, particularly a trifluoroacetamide, significantly reduced P-glycoprotein mediated efflux for the series proved essential. One of these novel bradykinin B1 antagonists (13b) also exhibited suitable pharmacokinetic properties and efficient ex vivo receptor occupancy for further development as a novel approach for the treatment of pain and inflammation.
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PMID:Development of orally bioavailable and CNS penetrant biphenylaminocyclopropane carboxamide bradykinin B1 receptor antagonists. 1722 69


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