Mechanisms of actions of opioids and non-steroidal anti-inflammatory drugs

New approaches to clarify antinociceptive and anti-inflammatory effects of the ethanol extract from Vernonia condensata leaves

The present study was aimed at evaluating the antinociceptive and anti-inflammatory effects of the ethanol extract from Vernonia condensata leaves in animal models, in order to afford a better understanding of these properties. The extract reduced the number of abdominal contortions at doses of 100 (51.00 ± 3.00), 200 (42.00 ± 2.98) and 400 mg/kg (39.00 ± 4.00). In formalin tests, a significant reduction in the licking time (p < 0.01) was observed in the first phase by 25.14 (200 mg/kg = 51.50 ± 4.44) and 31.15% (400 mg/kg = 48.00 ± 4.37). The doses of 100 (43.37 ± 5.15), 200 (34.62 ± 4.16) and 400 mg/kg (28.37 ± 3.98) inhibited (p < 0.001) the second phase. After 60 and 90 min of treatment, a dose of 400 mg/kg (10.13 ± 0.39 and 11.14 ± 1.33, respectively) increased the latency time. Doses of 200 and 400 mg/kg potentiated the sleeping time induced by diazepam, pentobarbital and meprobamate. The extracts (100, 200 and 400 mg/kg) showed anti-inflammatory effects by a decrease in paw edema. The extracts also reduced the exudate volume at the doses of 200 and 400 mg/kg. The leukocyte migration had significant effect (p < 0.001) at doses of 100, 200 and 400 mg/kg. The completion of additional experiments in the investigation of the antinociceptive and anti-inflammatory activities of V. condensata allowed a better understanding of the central and peripheral mechanisms involved.

Evolving therapeutic indications for N-type calcium channel blockers: from chronic pain to alcohol abuse

Clinical exploitation of the therapeutic potential of calcium channels has long been limited to L-type blockers for cardiovascular diseases. Recently, N-type blockers have been fully validated for the treatment of chronic pain, following approval of the intrathecally active ziconotide (Prialt(®)). This review describes the successful efforts to broaden the therapeutic scope of this mechanism to other major CNS indications, based on the discovery of N-type blockers orally active against pain. In animal models, the N-type blocker and pain-reducing NP078585 is efficacious against key elements of ethanol dependency, including self-administration and relapse. NP078585 moderately stimulates brain dopamine release without inducing reward or hyperlocomotion. N-type blockers may emerge as a novel class of 'dopamine stabilizers' for the treatment of drug dependency and other neuropsychiatric disorders without the side effects of current therapies.

Isolation of Bioactive Compounds That Relate to the Anti-Platelet Activity of Cymbopogon ambiguus

Infusions and decoctions of Cymbopogon ambiguus have been used traditionally in Australia for the treatment of headache, chest infections and muscle cramps. The aim of the present study was to screen and identify bioactive compounds from C. ambiguus that could explain this plant's anti-headache activity. A dichloromethane extract of C. ambiguus was identified as having activity in adenosine-diphosphate-induced human platelet aggregation and serotonin-release inhibition bioassays. Subsequent fractionation of this extract led to the isolation of four phenylpropenoids, eugenol, elemicin, eugenol methylether and trans-isoelemicin. While both eugenol and elemicin exhibited dose-dependent inhibition of ADP-induced human platelet serotonin release, only eugenol displayed potent inhibitory activity with an IC₅₀ value of 46.6 μM, in comparison to aspirin, with an IC₅₀ value of 46.1 μM. These findings provide evidence to support the therapeutic efficacy of C. ambiguus in the non-conventional treatment of headache and inflammatory conditions.

The duration of spinal anesthesia with 5% lidocaine in chronic opium abusers compared with nonabusers

BACKGROUND

It has been demonstrated that chronic opium abusers have lower thresholds for pain. In this study we sought to determine whether chronic opium abuse has any effect on the duration of spinal block by local anesthetics.

METHODS

In a case-controlled study, 50 opium abusers and 50 nonabusers undergoing lower abdomen operations were selected from among the patients admitted to a university hospital for elective surgery. All patients received 100 mg hyperbaric preservative-free 5% lidocaine in dextrose, intrathecally.

RESULTS

The duration of anesthesia was much shorter in the opium abusers (60 +/- 7 min) than in the nonabusers (83 +/- 10 min) (P < 0.0001).

CONCLUSION

The study documents a shortened duration of spinal block in opium abusers.

Aspirin compared with acetaminophen in the treatment of fever and other symptoms of upper respiratory tract infection in adults: a multicenter, randomized, double-blind, double-dummy, placebo-controlled, parallel-group, single-dose, 6-hour dose-ranging study

BACKGROUND

Aspirin (acetylsalicylic acid) and acetaminophen (paracetamol) are frequently used to treat fever and other symptoms of upper respiratory tract infection (URTI). Both are available over the counter for use at the standard recommended doses of 500 and 1000 mg per single use.

OBJECTIVE

This study investigated the efficacy, safety profiles, and tolerability of aspirin 500 and 1000 mg and acetaminophen 500 and 1000 mg compared with placebo in adult patients with acute febrile URTI of suspected viral origin.

METHODS

This was a multicenter, randomized, double-blind, double-dummy, placebo-controlled, parallel-group trial conducted in Ukraine and Russia. Patients with URTI and acute fever of > or =38.5 degrees C received a single dose of aspirin 500 or 1000 mg, acetaminophen 500 or 1000 mg, or matching placebo. Oral body temperature was measured in the clinic at specified time points up to 6 hours after dosing. The intensity of other symptoms of URTI was rated by patients at baseline and at 2, 4, and 6 hours after dosing (scale from 0 = none to 10 = severe). The primary efficacy measure was the AUC for the change in orally measured body temperature from the time of treatment (baseline) to 4 hours after dosing. Secondary outcome measures included the change in body temperature from baseline to specified time points between 0.5 and 6 hours after dosing, the difference between baseline and the lowest measured body temperature, the time to the lowest measured body temperature, and the intensity of other symptoms of URTI (ie, headache, sinus sensitivity to percussion, sore throat, achiness, and feverish discomfort). Tolerability was monitored by recording of adverse events.

RESULTS

Three hundred ninety-two patients were enrolled (78 in both aspirin groups, 79 in both acetaminophen groups, 78 in the placebo group). Demographic and baseline characteristics were comparable in the 5 groups; 51% of patients were male, with a mean age of 37.4 years and a mean body weight of 74.3 kg. The AUC values for the change in body temperature 0 to 4 hours after dosing were 3.18 (95% CI, 2.78-3.57) for aspirin 500 mg, 4.26 (95% CI, 3.84-4.68) for aspirin 1000 mg, 3.13 (95% CI, 2.77-3.49) for acetaminophen 500 mg, 4.11 (95% CI, 3.73-4.49) for acetaminophen 1000 mg, and 0.76 (95% CI, 0.38-1.13) for placebo. In terms of the primary efficacy variable, all active treatments were significantly superior to placebo (P < 0.001, 1-sided t test), with no significant differences between them. Reductions in body temperature were significantly greater with the 1000-mg doses of both active treatments compared with the 500-mg doses (P< 0.001, 1-sided t test). The mean maximum temperature reductions were 1.32 degrees C, 1.25 degrees C, 1.67 degrees C,1.71 degrees C, and 0.63 degrees C in the respective treatment groups. Significant reductions were seen in the mean intensity of headache, achiness, and feverish discomfort with all active treatments at most time points (P < 0.001), but not in sinus sensitivity to percussion or sore throat. All treatments were equally well tolerated, and no clinically significant adverse events occurred.

CONCLUSIONS

In this single-dose study, aspirin 500 and 1000 mg and acetaminophen 500 and 1000 mg were more effective against fever and other symptoms of URTI than placebo. Both active treatments showed dose-related efficacy, and there was no significant difference between equal doses of the 2 agents. Safety profiles and tolerability were also comparable between treatments.

Characterization of opioid receptors that modulate nociceptive neurotransmission in the trigeminocervical complex

1. Opioid agonists have been used for many years to treat all forms of headache, including migraine. We sought to characterize opioid receptors involved in craniovascular nociceptive pathways by in vivo microiontophoresis of micro -receptor agonists and antagonists onto neurons in the trigeminocervical complex of the cat. 2. Cats were anaesthetized with alpha-chloralose 60 mg kg(-1), i.p. and 20 mg kg(-1), i.v. supplements after induction and surgical preparation using halothane. Units were identified in the trigeminocervical complex responding to supramaximal electrical stimulation of the superior sagittal sinus, and extracellular recordings of activity made. 3. Seven- or nine-barrelled glass micropipettes incorporating tungsten recording electrodes in their centre barrels were used for microiontophoresis of test substances onto cell bodies. 4. Superior sagittal sinus (SSS)-linked cells whose firing was evoked by microiontophoretic application of L-glutamate (n=8 cells) were reversibly inhibited by microiontophoresis of H(2)N-Tyr-D-Ala-Gly-N-Me-Phe-Gly-ol (DAMGO) (n=12), a selective micro -receptor agonist, in a dose dependent manner, but not by control ejection of sodium or chloride ions from a barrel containing saline. 5. The inhibition by DAMGO of SSS-linked neurons activated with L-glutamate could be antagonized by microiontophoresis of selective micro -receptor antagonists D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH(2) (CTOP) or D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH(2) (CTAP), or both, in all cells tested (n=4 and 6, respectively). 6. Local iontophoresis of DAMGO during stimulation of the superior sagittal sinus resulted in a reduction in SSS-evoked activity. This effect was substantially reversed 10 min after cessation of iontophoresis. The effect of DAMGO was markedly inhibited by co-iontophoresis of CTAP. 7. Thus, we found that micro -receptors modulate nociceptive input to the trigeminocervical complex. Characterizing the sub-types of opioid receptors that influence trigeminovascular nociceptive transmission is an important component to understanding the pharmacology of this synapse, which is pivotal in primary neurovascular headache.

COX-3, a cyclooxygenase-1 variant inhibited by acetaminophen and other analgesic/antipyretic drugs: cloning, structure, and expression

Two cyclooxygenase isozymes, COX-1 and -2, are known to catalyze the rate-limiting step of prostaglandin synthesis and are the targets of nonsteroidal antiinflammatory drugs. Here we describe a third distinct COX isozyme, COX-3, as well as two smaller COX-1-derived proteins (partial COX-1 or PCOX-1 proteins). COX-3 and one of the PCOX-1 proteins (PCOX-1a) are made from the COX-1 gene but retain intron 1 in their mRNAs. PCOX-1 proteins additionally contain an in-frame deletion of exons 5-8 of the COX-1 mRNA. COX-3 and PCOX mRNAs are expressed in canine cerebral cortex and in lesser amounts in other tissues analyzed. In human, COX-3 mRNA is expressed as an approximately 5.2-kb transcript and is most abundant in cerebral cortex and heart. Intron 1 is conserved in length and in sequence in mammalian COX-1 genes. This intron contains an ORF that introduces an insertion of 30-34 aa, depending on the mammalian species, into the hydrophobic signal peptide that directs COX-1 into the lumen of the endoplasmic reticulum and nuclear envelope. COX-3 and PCOX-1a are expressed efficiently in insect cells as membrane-bound proteins. The signal peptide is not cleaved from either protein and both proteins are glycosylated. COX-3, but not PCOX-1a, possesses glycosylation-dependent cyclooxygenase activity. Comparison of canine COX-3 activity with murine COX-1 and -2 demonstrates that this enzyme is selectively inhibited by analgesic/antipyretic drugs such as acetaminophen, phenacetin, antipyrine, and dipyrone, and is potently inhibited by some nonsteroidal antiinflammatory drugs. Thus, inhibition of COX-3 could represent a primary central mechanism by which these drugs decrease pain and possibly fever.

Comparison of the morphine-sparing effects of diclofenac sodium and ketorolac tromethamine after major orthopedic surgery

STUDY OBJECTIVES

To compare the efficacy of diclofenac sodium with ketorolac tromethamine in reducing postoperative morphine use after major orthopedic surgery.

DESIGN

Double-blind, randomized, placebo-controlled study.

SETTING

Major teaching institution.

PATIENTS

102 ASA physical status II patients undergoing hip and knee replacement with general anesthesia.

INTERVENTIONS

Before induction of anesthesia, patients were randomly allocated to receive intravenously either diclofenac sodium 75 mg (Group D), ketorolac tromethamine 60 mg (Group K), or placebo (Group P). Patient-controlled analgesia was supplied postoperatively using morphine.

MEASUREMENTS

Visual analog scale (VAS), verbal pain score (VPS), sedation score, frequency of opioid side effects, and morphine consumption were recorded every 4 hours.

MAIN RESULTS

There was a highly significant downward trend for VAS, VPS, and sedation scores over time, p = 0.001. The mean VAS and VPS scores were significantly lower in Groups D and K compared with Group P at time 0, p = 0.009 and 8 hours, p = 0.026. The mean (SD) 24-hour morphine requirements were 36.3 mg (16.9), 47.2 mg (34.9), and 51.6 mg (22.2) for Groups D, K, and P, respectively, p = 0.032. Fewer patients suffered from postoperative nausea and vomiting in the treatment groups (Groups D and K) compared with Group P (9, 8, and 19, respectively), p < 0.05. Fewer patients also suffered from pruritus in Groups D and K compared with Group P (3, 4, and 11, respectively), p < 0.01.

CONCLUSIONS

Preoperative administration of intravenous diclofenac 75 mg or ketorolac 60 mg significantly reduces morphine requirements and associated side effects after major orthopedic surgery.

The influence of divalent cations on the analgesic effect of opioid and non-opioid drugs

It is generally accepted that divalent cations are involved in the nociceptive pathway. The effect of systemic co-administration of magnesium sulfate and calcium channel blockers (nifedipine, verapamil) on the analgesic effect of opioid (mixed mu/kappa: butorphanol) and non-opioid drugs (paracetamol) was investigated. Albino mice and rats were used as experimental animals. Magnesium sulfate and calcium channel blockers were given i.p., 30 min before the administration of butorphanol tartrate and paracetamol. Analgesia was measured using "hot-plate" ( 52.5( composite function)C), "tail-flick" (radiant heat source), "writhing" (acetic acid, 1%, i.p.) and "tail-clip" tests. The pain threshold was evaluated before and after the administration (i.p.) of the different agents. The effect of the combined administration of different agents on behavior, blood pressure and heart rate, was also determined. Nifedipine (5 mg kg(-1), i.p.) and verapamil (10 mg kg(-1), i.p.) potentiated the analgesic effect of butorphanol tartrate (0.25-2 mg kg(-1), i.p.) in all tests (synergism) and enhanced analgesic effect of paracetamol (50-125 mg kg(-1), i.p.), only in acetic acid writhing and tail-clip tests. Magensium sulfate (2.5 mg kg(-1), i.p.) potentiated the analgesic effect of butorphanol, but not that of paracetamol. Co-administration of nifedipine and verapamil with either of butorphanol (0.25-2 mg kg(-1)) or paracetamol (50-125 mg kg(-1), i.p.) produced no significant effects on motor coordination, motor performance, locomotor activity, long-term memory or on the blood pressure and heart rate of experimental animals. Co-administration of magnesium sulfate, however, significantly induced sedation, inhibition of locomotor activity, motor performance and coordination, as well as impairing of long-term memory, as compared with butorphanol and paracetamol, administered alone. We conclude that the systemic co-administration of calcium channel blockers potentiated the analgesic effect of butorphanol against thermal, mechanical and chemical pain but enhanced that of paracetamol only against mechanical and chemical pain. Magensium sulfate enhanced the analgesic effect of butorphanol, but not that of paracetamol. These findings, merit further studies in animals and humans to evaluate the potential therapeutic benefits of such interactions.

Inhibition of phospholipase A(2) as a therapeutic target

The hydrolysis of cell membrane phospholipids by phospholipase A(2) (PLA(2)) leads to the production of numerous lipid mediators of diverse pathological conditions, mainly inflammatory diseases. These include lysophospholipids and their derivatives, and arachidonic acid and its derivatives (the eicosanoids). Both these groups of mediators are produced predominantly by the secretory PLA(2)s (sPLA(2)s) which hydrolyze the phospholipids of the cell surface membrane. Protection of cell membrane from these 'inflammatory enzymes' can therefore be used for the treatment of inflammatory processes. A prototype of cell-impermeable PLA(2) inhibitors, which protect the cell membrane from different sPLA(2)s without affecting vital phospholipid metabolism, is presented and discussed in the present review.

The use of analgesics in the management of pain in rheumatic diseases

Pain is the most common complaint of patients who see rheumatologists. In this article, the current treatment options for pain are reviewed; these include acetaminophen, nonsteroidal anti-inflammatory drugs, new specific cyclooxygenase-2 inhibitors, opioid analgesics, centrally acting muscle relaxants, antidepressants, and topical analgesics and counterirritants. The doses of medication and known adverse effects of these medications are highlighted.