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If 'atypical' neuroleptics did not exist, it wouldn't be necessary to invent them: perverse incentives in drug development, research, marketing and clinical practice.

Perverse incentives in drug development, research, marketing and clinical usage can be illustrated by considering the example of the so-called 'atypical' neuroleptics which have grown to become a standard - indeed expanding - part of psychiatric practice despite their probable inferiority to older sedative agents. There is now ample evidence to suggest that neuroleptics (aka. anti-psychotics and major tranquillizers) are dangerous drugs, and patients' exposure to them should be minimized wherever possible. This clinical imperative applies whether neuroleptics are of the traditional type or atypical variety, albeit for different reasons since the traditional agents are neurotoxic, while atypicals are mainly metabolic poisons. Usage of traditional neuroleptics seems indeed to be declining progressively, but the opposite seems to be happening for 'atypicals', and new indications for these drugs are being promoted. Yet the atypical neuroleptics are a category of pharmaceuticals which are close to being un-necessary since there are safer, cheaper and pleasanter substitutes, such as benzodiazepines and the sedative antihistamines (e.g. promethazine). If 'atypical' neuroleptics did not exist, it would not be necessary to invent them. Analysis of how such expensive, dangerous and inferior drugs as the 'atypicals' have nevertheless come to dominate clinical practice casts light on the perverse incentives which now motivate the pharmaceutical industry in an era of massive state regulation. The lack of positive incentives to deploy off-patent drugs is longstanding, but there is a new disincentive in the widespread but erroneous belief that only randomized controlled trials (RCTs) can provide valid 'evidence' of effectiveness. Consequently, those who control RCTs now control clinical practice. It sometimes makes commercial sense to develop and market new drugs that are inferior to existing agents, since new drugs are patent-protected and can be promoted on the back of a mass of new RCTs funded and 'owned' by the pharmaceutical corporations. The current regulatory and patenting situation, therefore, requires major reform if drug efficacy and patient safety are to become higher priorities. Given that psychiatric practice is apparently 'locked-in' to prescribing atypicals, and if (as seems likely) most informed individuals would wish to avoid neuroleptics for themselves and their loved-ones except as a last resort; then in the short-term it may be wise for patients and their families to explore the possibilities of increased self-management of psychiatric problems using over-the-counter drugs, such as the sedative antihistamines. In the long-term, there need to be legal reforms to change the regulatory and commercial framework of incentives relating to drug development. These might include new forms of short-term re-patenting of old drugs.

Antipsychotic Agents↗

A randomized, placebo-controlled trial of corticosteroids for hyperemesis due to pregnancy.

OBJECTIVE: Hyperemesis gravidarum, a severe form of nausea and vomiting due to pregnancy for which there is no proven pharmacological treatment, is the third leading cause for hospitalization during pregnancy. Corticosteroids are commonly used for the treatment of nausea and vomiting due to cancer chemotherapy-induced emesis and might prove useful in hyperemesis gravidarum. METHODS: A randomized, double-blind, placebo-controlled trial was conducted in 126 women who previously had not responded to outpatient therapy for hyperemesis gravidarum during the first half of pregnancy. Intravenous methylprednisolone (125 mg) was followed by an oral prednisone taper (40 mg for 1 day, 20 mg for 3 days, 10 mg for 3 days, 5 mg for 7 days) versus an identical-appearing placebo regimen. All women also received promethazine 25 mg and metoclopramide 10 mg intravenously every 6 hours for 24 hours, followed by the same regimen administered orally as needed until discharge. The primary study outcome was the number of women requiring rehospitalization for hyperemesis gravidarum. RESULTS: A total of 110 women delivered at our hospital and had pregnancy outcomes available for analysis; 56 were randomized to corticosteroids and 54 were administered placebo. Nineteen women in each study group required rehospitalization (34% versus 35%, P =.89, for corticosteroids versus placebo, respectively). CONCLUSION: The addition of parenteral and oral corticosteroids to the treatment of women with hyperemesis gravidarum did not reduce the need for rehospitalization later in pregnancy.

Adolescent↗

The use of levomepromazine in Hyperemesis Gravidarum resistant to drug therapy--a case series.

Hyperemesis Gravidarum (HG) is a potentially serious complication of early pregnancy, which may rarely be severe enough to warrant termination of pregnancy. HG requires prompt treatment with intravenous fluids, thiamine supplementation and appropriate anti-emetic therapy. Anti-histamines such as promethazine are favoured as first-line agents, with prochlorperazine being used as a second-line drug. However, there is no clear data as to the most appropriate drug if these are ineffective. A case series of six women who presented with HG resistant to drug treatment is described. In these cases, levomepromazine 6.25mg tds was used to control HG. Five pregnancies progressed leading to live born infants with no evidence of congenital anomaly. One pregnancy resulted in an intra-uterine death with no external or ultrasound evidence of congenital anomaly. The role of phenothiazines in the pharmacological management of HG is discussed.

Adolescent↗

Interaction between chloroquine and diverse pharmacological agents in chloroquine resistant Plasmodium yoelii nigeriensis.

The effect of a number of pharmacological agents on the enhancement of antimalarial activity of chloroquine was evaluated against chloroquine resistant line of Plasmodium yoelii nigeriensis (N-67). The response after combination therapy was monitored on the basis of alteration in the course of parasitaemia, the extension of mean survival time and the percent cure rate in different groups. The study was designed to compare the in vivo efficacy of a number of resistance modulating agents found effective in several in vitro studies against chloroquine resistant P. falciparum isolates. Based on their efficacy in this rodent model, the response of combination of chloroquine with agents representing diverse chemical moieties has been categorised as curative, moderately active and inactive. Out of the 22 agents evaluated, only cyproheptadine-chloroquine combination produced curative response. Ketotifen, azatadine, pheniramine, amitriptyline, fluoxetine, verapamil, penfluridol and trifluoperazine demonstrated moderate activity while loratadine, terfenadine, promethazine, ranitidine, nifedipine, diltiazem, chlorpromazine, amiodarone, tamoxifen, dipyridamol, propranolol, acyclovir and amantidine were inactive. The study advocates the suitability of proposed rodent model to shortlist potential resistance reversal agents.

Animals↗

[Anti-cholinergic effect of Pluchea ovalis (pers.) Dc. (asteraceae) root extract on isolated Wistar rat tracheae].

Ethanolic extract of Pluchea ovalis roots inhibit acetylcholine-induced bronchoconstriction observed in asthma. To understand the mechanism of P. ovalis root extract on airway smooth muscle contraction, we investigated the anti-cholinergic effect of the ethanolic extract on isolated isolated tracheae of the Wistar rat. For this purpose, three experimental conditions of incubation were used: idomethacin, indomethacin+propranolol or indomethacin+propranolo+ promethazine. The extract was applied in all three conditions at 0.25 mg/ml for 10 minutes prior to cumulative doses of acetylcholine (10(-8) to 5.10(-4) g/ml). The extract reduced acetylcholine-induced contraction and could have an antagonistic effect on muscarinic receptors of the rat trachea.

Acetylcholine↗

tert-Butyl hydroperoxide-induced lipid signaling in hepatocytes: involvement of glutathione and free radicals.

tert-Butyl hydroperoxide (TBHP) mobilizes arachidonic acid (AA) from membrane phospholipids in rat hepatocytes under cytotoxic conditions, thus leading to an increase in intracellular AA, which precedes cell death. In the present work, the involvement of lipid peroxidation, thiol status, and reactive oxygen species (ROS) in the intracellular AA accumulation induced by 0.5 mM TBHP was studied in rat hepatocytes. Cells treated with TBHP maintained viability and energy status at 10 min. However, TBHP depleted GSH, as well as inducing lipid peroxidation and ROS formation, detected by dichlorofluorescein (DCF) fluorescence. TBHP also significantly increased (32.5%) the intracellular [14C]-AA from [14C]-AA-labelled hepatocytes. The phospholipase A(2) (PLA(2)) inhibitor, mepacrine, completely inhibited the [14C]-AA response. The addition of antioxidants to the cell suspensions affected the TBHP-induced lipid response differently. The [14C]-AA accumulation correlated directly with ROS and negatively with endogenous GSH. No correlation between [14C]-AA and lipid peroxidation was found. Promethazine prevented lipid peroxidation and did not affect the [14C]-AA increase. We conclude that TBHP stimulates the release of [14C]-AA from membrane phospholipids through a PLA(2)-mediated mechanism. Endogenous GSH and ROS play a major role in this effect, while lipid peroxidation-related events are unlikely to be involved. Results suggest that specific ROS generated in iron-dependent reactions, different from lipid peroxyl radicals, are involved in PLA(2) activation, this process being important in TBHP-induced hepatocyte injury.

Animals↗

Chlorpromazine reduces toxicity and Ca2+ uptake induced by amyloid beta protein (25-35) in vitro.

Amyloid beta protein (A beta), has been reported to be toxic to neurons in vitro. However, the molecular mechanism leading to neuronal death remains unknown. Here we report protective effects of phenothiazines, a class of neuroleptic agent, against A beta toxicity in primary cultures of rat cortical neurons and PC12 cells. beta(25-35), an active sequence of A beta, showed dose-dependent reduction of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide dye (MTT) reductivity, and chlorpromazine (CPZ), promethazine or trifluoperazine restored it at micromolar concentration. The significant increase in Ca2+ uptake by chronic treatment of beta(25-35) was reduced not only by nimodipine but also by CPZ. These results suggest that phenothiazines attenuate beta(25-35) toxicity possibly by reducing of Ca2+ influx through L-type Ca2+ channels.

Amyloid beta-Peptides↗

Continuous intravenous versus bolus parenteral midazolam: a safe technique for conscious sedation in plastic surgery.

Conscious intravenous sedation is a safe alternative method to general anaesthesia. We have used a technique of continuously titrated, as opposed to incremental boluses of, intravenous or intramuscular midazolam for conscious sedation, with tumescent adrenaline-lignocaine solution for local anaesthesia, routinely in 421 plastic surgical procedures between 1997 and 2000. All patients were American Society of Anesthesiologists (ASA) class I or II. Conscious sedation was administered through our protocol of continuously titrated doses of midazolam in dextrose saline. The operative field was injected subcutaneously with varying volumes of diluted lignocaine and adrenaline, depending on the anatomical region. Preoperative sedation was administered 1 h before the procedure in the form of an intramuscular injection of pethidine and promethazine (Phenergan). Intraoperatively, a subset of patients received up to four divided diluted doses of pethidine. A preoperative 4 h starvation period pronounced the effect of the sedative. No intraoperative conversions to general anaesthesia were needed, and no sedation complications occurred. No unplanned re-admissions secondary to nausea, prolonged drowsiness or pain were required. All patients who were treated using this technique had an uneventful postoperative course. Hospital stay was substantially shorter than following general anaesthesia, which provided a significant reduction in medical-care expenses and a faster return to work. In conclusion, conscious sedation administered by titrated intravenous midazolam is a well-tolerated, safe, consistent, predictable and effective anaesthetic choice for a variety of plastic surgical procedures, many of which would commonly be performed under general anaesthesia.

Adolescent↗

Modulation of emesis by fentanyl and opioid receptor antagonists in Suncus murinus (house musk shrew).

The anti-emetic mechanism of action of fentanyl to inhibit nicotine (5 mg/kg, s.c.)-induced emesis was investigated in Suncus murinus. The anti-emetic action of fentanyl (40 microg/kg, s.c.) was antagonised by the opioid receptor antagonists naltrexone (1 mg/kg, s.c.), naloxone (1 mg/kg, s.c.), M8008 (16S-methylcyprenorphine; 1 mg/kg, s.c.) and MR 2266 (5,9-diethyl-2-(3-furylmethyl)2'-hydroxy-7,7-benzomorphan; 1 mg/kg) but not by naloxone methylbromide (1 mg/kg, s.c.), naloxone methyliodide (1 mg/kg, s.c.), naltrindole (1 mg/kg, s.c.), DIPPA (2-(3,4-dichlorophenyl)-N-methyl-N-[1S)-1-(3-isothiocyanatophenyl)-2-(1- pyrrolidinyl)-ethyl]acetamide; 3 mg/kg, i.p.) or naloxonazine (35 mg/kg, i.p.). This indicates an involvement of mu2-opioid receptors within the brain to mediate the anti-emetic effect of fentanyl. In other studies, naloxone 10-60 mg/kg, s.c. induced dose-related emesis but naltrexone was only emetic at 60 mg/kg, s.c. and naloxone methylbromide failed to induce emesis at doses up to 60 mg/kg, s.c. The emesis induced by a high dose of naloxone 60 mg/kg, s.c. was antagonized by CP-99,994 ((+)-(2S,3S)-3-(2-methoxybenzylamino)-2-phenylpiperidine; 3-30 mg/kg, i.p.), 8-OH-DPAT, ((+/-)-8-hydroxy-dipropylaminotetralin; 0.003-0.3 mg/kg, s.c.), buspirone (3 mg/kg, s.c.) and fluphenazine (1-3 mg/kg, i.p.) but not by naltrexone (1-30 mg/kg, s.c.), metoclopramide (0.3-3 mg/kg, i.p.), sulpiride (0.3-3 mg/kg, i.p.), domperidone (0.1-3 mg/kg, i.p.), ondansetron (0.3-3 mg/kg, i.p.), granisetron (0.3-3 mg/kg, i.p.), scopolamine (0.3-3 mg/kg, i.p.) or promethazine (0.3-3 mg/kg, i.p.). The data is discussed in relation to opioid receptor mechanisms moderating emesis and the identification of potential sites of drug action available to inhibit the emetic reflex.

Animals↗

Conscious sedation for in vitro fertilization.

OBJECTIVE: To review the principles and practice of the use of conscious sedation for IVF. DESIGN: The pertinent literature was reviewed and recommendations are provided. RESULT(S): Conscious sedation appears to be the most commonly used method of pain relief for transvaginal retrieval of oocytes. Conscious sedation does not require the presence of an anesthesiologist and can be done in freestanding clinics. Agents commonly used include opioids in combination with benzodiazepines. This combination minimizes pain, decreases anxiety, and provides sedation and some amnesia. Adjuvants such as promethazine and hydroxyzine can also be used but often are not needed. Conscious sedation is well tolerated by patients and does not require highly specialized equipment. However, there are specific safeguards that should be followed. Only a few toxicity studies have been performed, but they are reassuring because they have not found significant effects on fertilization or cleavage. CONCLUSION(S): Conscious sedation appears to be a safe and cost-effective method of providing analgesia and anesthesia for transvaginal retrieval of oocytes.

Benzodiazepines↗

Gas chromatographic determination of propoxyphene and norpropoxyphene in plasma.

Propoxyphene and its major metabolite norpropoxyphene have been determined simultaneously by using gas chromatography. In order to avoid the on-column decomposition of the propoxyphene, derivatives were formed with the aid of lithium aluminium hydride, which cleaves the propionic acid ester of propoxyphene and reduces the norpropoxyphene amide. Promethazine was used as an internal standard. Propoxyphene and norpropoxyphene levels in plasma were determined in samples from six male volunteers receiving a single oral dose of 150 mg of propoxyphene hydrochloride in a sustained-release form (Abalgin Retard).

Chemical Phenomena↗

Enantioseparation of phenothiazines in cyclodextrin-modified micellar electrokinetic chromatography.

In this study, enantioseparations of five phenothiazines in cyclodextrin (CD)-modified micellar electrokinetic chromatography (MEKC) were investigated using a citrate buffer containing tetradecyltrimethylammonium bromide (TTAB) as a cationic surfactant at low pH. Beta-cyclodextrin (beta-CD) and hydroxylpropyl-beta-CD (HP-beta-CD) were selected as chiral selectors. The results indicate that the separation window is greatly enlarged by beta-CD concentration and that the separability and selectivity of phenothiazines are remarkably influenced by the concentrations of both beta-CD and TTAB, as well as buffer pH. The interaction of thioridazine with beta-CDs is considerably reduced in the presence of TTAB micelles due to competitive complexation of thioridazine with TTAB micelles, which is pH-dependent. As a result, effective enantioseparation of thioridazine is simultaneously achievable with that of trimeprazine and promethazine or ethopropazine in MEKC with addition of either beta-CD or HP-beta-CD, respectively, to a micellar citrate buffer containing TTAB at pH 3.5. Better enantioresolution of thioridazine in MEKC than in capillary zone electrophoresis can be obtained.

Chromatography, Micellar Electrokinetic Capillary↗

The effect of phenothiazines upon maintenance of membrane integrity in the cultured myocardial cell.

The cultured myocardial cell provides a defined model for examining factors which are responsible for maintaining cellular viability and sarcolemmal integrity. Our data indicates that the spontaneous loss of myocyte membrane integrity is a calcium-dependent process and thus provides a method for examining the mechanism through which calcium exerts this effect. Antimyosin antibody staining and propidium iodide uptake were used to quantitate membrane integrity. The integrity of the cell membrane was inversely related to the calcium concentration in the culture medium. This loss of membrane integrity was calmodulin-dependent as demonstrated by the following: phenothiazines (trifluoperazine greater than chlorpromazine greater than promethazine) and structurally dissimilar calmodulin-inhibitors prevented the formation of sarcolemmal defects at concentrations similar to those known to inhibit calmodulin; phenothiazines and calcium demonstrated a competitive interaction with respect to this effect on membrane integrity. Electron microscopy confirmed the integrity of the sarcolemma of the cells exposed to high phenothiazine concentrations although metabolic alterations occurred in these cells as evidenced by an increased membrane permeability to the low molecular weight probe propidium iodide, degenerative changes in the fine structure of the mitochondria, the accumulation of autophagic vacuoles in the cytoplasm and the loss of contractile ability. These findings indicate that calmodulin inhibitory compounds are capable of preserving the membrane integrity of cardiac myocytes, interfering with a calcium-dependent process that is associated with the spontaneous attrition of these cells in culture. Significant intracellular alterations appear at high doses of these agents even while the sarcolemma is free of gross defects.

Animals↗

Putative identification of functional interactions between DNA intercalating agents and topoisomerase II using the V79 in vitro micronucleus assay.

Clastogenicity is frequently observed following treatment of mammalian cells with new chemical entities. This clastogenicity, unless proven otherwise, is assumed to result from the imperfect repair of DNA lesions produced from covalent chemical/DNA interaction. However, clastogenicity can also arise via other mechanisms such as non-covalent chemical intercalation into DNA resulting in poisoning of cellular DNA topoisomerase II (topo II) and stabilization of DNA double strand breaks. We have recently reported modifications to the V79 in vitro micronucleus assay which allow an indirect evaluation of both the intercalative and topoisomerase-interactive activities of chemical agents. In the present studies we have used these modified assays to further assess the validity of this approach in an evaluation of a number of intercalating and non-intercalating polycyclic compounds. It is shown that intercalating agents may be catalytic topo II inhibitors (e.g. chloroquine (CHL), tacrine (TAC), 9-aminoacridine (9AA), ethidium bromide (EB)) or topo II poisons (e.g. proflavine (PROF), auramine O (AUR) and curcumin (CURC)). Still other intercalators are shown to lack detectable topo II-interactions, (e.g. imipramine (IMP), quinacrine (QUIN), 2-aminoanthracene (AA), iminostilbene (IMN) and promethazine (PHE)). It is concluded that (1) the clastogenicity of three agents, PROF (a typical DNA intercalating agent), and AUR and CURC (both structurally atypical intercalating agents, with unknown clastogenic mechanisms), may be due to topo II poisoning; (2) other intercalating agents may either act as catalytic topo II inhibitors or exhibit no functional topo II interaction; (3) The use of these cell-based approaches may provide a logical first step in determining if unexpected clastogenicity associated with test article exposure is due to a topo II interaction.

Animals↗

Pharmacological characterisation of the human small conductance calcium-activated potassium channel hSK3 reveals sensitivity to tricyclic antidepressants and antipsychotic phenothiazines.

A stable CHO-K1 cell line was developed which expresses the human small conductance calcium-activated potassium channel hSK3. Immunofluorescence microscopy using an anti-SK3 antibody and radioligand binding using [(125)I]-apamin demonstrated the presence of hSK3 channel in the recombinant cell line. This cell line was utilised in a fluorescence assay using the membrane potential-sensitive dye DiBAC(4)(3) to functionally analyse and pharmacologically characterise this potassium channel. The analysis of known blockers of calcium-activated potassium channels revealed the highest potency for apamin (IC(50)=13.2 nM). This result was confirmed by direct recordings of SK3 currents using the whole-cell patch-clamp technique. Tricyclic antidepressants such as desipramine, imipramine and nortriptyline as well as phenothiazines such as fluphenazine, promethazine, chlorpromazine and trifluoperazine blocked the hSK3 channel with micromolar potencies. These compounds also displaced [(125)I]-apamin binding to the hSK3 channel thus suggesting direct and competitive channel blocking activity. Since these compounds share a common three-ring molecular core structure, this feature seems to be important for channel blocking activity. The serine/threonine protein phosphatase inhibitors okadaic acid and calyculin A were able to abolish channel activation with nanomolar potencies, but did not displace [(125)I]-apamin binding. Thus, phosphorylation of hSK3 or an accessory channel subunit seems to be involved in its modulation.

Animals↗

Adverse neuropsychiatric effects of dopamine antagonist medications. Misdiagnosis in the medical setting.

Medications with central dopamine antagonist properties are in wide use in treating a variety of medical symptoms. Some of the most commonly used are metoclopramide (Reglan), prochlorperazine (Compazine), droperidol (Inapsine), and promethazine (Phenergan). The major adverse neuropsychiatric effects seen with these medications are acute dystonias, akathisia, parkinsonian symptoms, and neuroleptic malignant syndrome. These effects are often unrecognized or misdiagnosed by the primary physician as functional psychiatric disorders. The authors present four cases in which adverse neuropsychiatric effects from metoclopramide and prochlorperazine occurred with patients in the general hospital, and they discuss their initial misdiagnosis and subsequent identification and treatment by the consulting psychiatrist. The literature is reviewed on the adverse neuropsychiatric effects of metoclopramide and prochlorperazine, with attention to patient populations at risk. The authors believe that there is a key role in this area for the consulting psychiatrist, who can provide diagnostic clarity, advice on management, and ongoing staff education.

Adult↗

Bradykinin is involved in hyperalgesia induced by Bothrops jararaca venom.

Bradykinin is involved in hyperalgesia (pain hypersensitivity) induced by Bothrops jararaca venom-intraplantar injection of B. jararaca venom (5microg/paw) in rats caused hyperalgesia, which peaked 1h after venom injection. This phenomenon was not modified by promethazine (H(1) receptor antagonist), methysergide (5-HT receptor antagonist), guanethidine (sympathetic function inhibitor), anti-TNF-alpha or anti-interleukin-1 antibodies or by the chelating agent CaNa(2)EDTA. Venom-induced hyperalgesia was blocked by the bradykinin B(2) receptor antagonist HOE 140. On the other hand, des-Arg(9), [Leu(8)]-bradykinin, a bradykinin B(1) receptor antagonist, did not modify the hyperalgesic response. These results suggest that bradykinin, acting on B(2) receptor, is a mediator of hyperalgesia induced by B. jararaca venom.

Adrenergic beta-Antagonists↗

Hyperalgesia induced by Asp49 and Lys49 phospholipases A2 from Bothrops asper snake venom: pharmacological mediation and molecular determinants.

The ability of Lys49 and Asp49 phospholipases A(2) (PLA(2)), from Bothrops asper snake venom, to cause hyperalgesia was investigated in rats, using the paw pressure test. Intraplantar injection of both toxins (5-20 micro g/paw) caused hyperalgesia, which peaked 1h after injections. Incubation of both proteins with heparin, prior to their injection, partially reduced this response. Chemical modification of Asp49 PLA(2) with p-bromophenacyl bromide (p-BPB), which abrogates its PLA(2) activity, also abolished hyperalgesia. Intraplantar injection of a synthetic peptide corresponding to the C-terminal sequence 115-129 of Lys49 PLA(2), caused hyperalgesia of similar time course, but varying magnitude, than that induced by the native protein. In contrast, a homologous peptide derived from the Asp49 PLA(2) did not show any nociceptive effect. Hyperalgesia induced by both PLA(2)s was blocked by the histamine and serotonin receptor antagonists promethazine and methysergide, respectively, by the bradykinin B(2) receptor antagonist HOE 140 and by antibodies to tumor necrosis factor alfa (TNFalpha) and interleukin 1 (IL-1). Pretreatment with guanethidine, atenolol, prazosin and yohimbine, inhibitors of sympathomimetic amines, or with indomethacin, inhibitor of the cyclo-oxygenase pathway, reduced Lys49 PLA(2)-induced hyperalgesia without interfering with the nociceptive activity of Asp49 PLA(2). The hyperalgesic response to both myotoxins was not modified by pretreatment with celecoxib, an inhibitor of the cyclo-oxygenase type II, by zileuton, an inhibitor of the lipoxygenase pathway or by N(g)-methyl-L-arginine (LNMMA), an inhibitor of nitric oxide synthase. These results suggest that Asp49 and Lys49 PLA(2)s are important hyperalgesic components of B. asper venom, and that Lys49 and Asp49 PLA(2)s exert their algogenic actions through different molecular mechanisms.

Animals↗