Paracetamol: new vistas of an old drug

Adamantyl analogues of paracetamol as potent analgesic drugs via inhibition of TRPA1

Paracetamol also known as acetaminophen, is a widely used analgesic and antipyretic agent. We report the synthesis and biological evaluation of adamantyl analogues of paracetamol with important analgesic properties. The mechanism of nociception of compound 6a/b, an analog of paracetamol, is not exerted through direct interaction with cannabinoid receptors, nor by inhibiting COX. It behaves as an interesting selective TRPA1 channel antagonist, which may be responsible for its analgesic properties, whereas it has no effect on the TRPM8 nor TRPV1 channels. The possibility of replacing a phenyl ring by an adamantyl ring opens new avenues in other fields of medicinal chemistry.

Preparation, spectroscopic, thermal, antihepatotoxicity, hematological parameters and liver antioxidant capacity characterizations of Cd(II), Hg(II), and Pb(II) mononuclear complexes of paracetamol anti-inflammatory drug

Keeping in view that some metal complexes are found to be more potent than their parent drugs, therefore, our present paper aimed to synthesized Cd(II), Hg(II) and Pb(II) complexes of paracetamol (Para) anti-inflammatory drug. Paracetamol complexes with general formula [M(Para)2(H2O)2]·nH2O have been synthesized and characterized on the basis of elemental analysis, conductivity, IR and thermal (TG/DTG), (1)H NMR, electronic spectral studies. The conductivity data of these complexes have non-electrolytic nature. Comparative antimicrobial (bacteria and fungi) behaviors and molecular weights of paracetamol with their complexes have been studied. In vivo the antihepatotoxicity effect and some liver function parameters levels (serum total protein, ALT, AST, and LDH) were measured. Hematological parameters and liver antioxidant capacities of both Para and their complexes were performed. The Cd(2+)+Para complex was recorded amelioration of antioxidant capacities in liver homogenates compared to other Para complexes treated groups.

Comparison of clinical efficacy of intravenous acetaminophen with intravenous morphine in acute renal colic: a randomized, double-blind, controlled trial

The aim of this study was to compare the clinical efficacy of intravenous acetaminophen with intravenous morphine in acute renal colic pain management. In this double-blind controlled trial, patients aged 18–55 years, diagnosed with acute renal colic, who met the inclusion and exclusion criteria, were randomized into two groups. First, using the visual analogue scale (VAS), intensity of pain was assessed in both groups. Then, one gram of intravenous acetaminophen or 0.1 mg/kg morphine was infused in 100 mL normal saline to either acetaminophen or morphine group. Intensity of pain was reassessed in 15, 30, 45, and 60 minutes according to VAS criteria. Finally, data from 108 patients were analyzed, 54 patients in each group. No significant difference was observed between the two groups in regard to sex (P = 0.13), mean age (P = 0.54), and baseline visual analogue score (P = 0.21). A repeated measure analysis of variance revealed that the difference between the two treatments was significant (P = 0.0001). The VAS reduction at primary endpoint (30 min after drug administration) was significantly higher in the acetaminophen group than in the morphine group (P = 0.0001). This study demonstrated that intravenous acetaminophen could be more effective than intravenous morphine in acute renal colic patients' pain relief.

Chitosan and blueberry treatment induces arginase activity and inhibits nitric oxide production during acetaminophen-induced hepatotoxicity

Background:

Liver diseases have become a major problem of the worldwide. More than 50% of all cases of liver failure can be attributed to drugs. Among these, acetaminophen is the most common cause.

Objective:

The aim of this study was to investigate the the hepatoprotective effects of blueberry and chitosan on tissue arginase activity, ornithine and nitric oxide levels during the acetaminophen-induced hepatotoxicity.

Materials and Methods:

Acetaminophen (250 mg/kg body weight per day), blueberry (60 mg/kg body weight per day) and, chitosan (200 mg/kg body weight per day) were administered to the rats by oral gavage during the experimental period.

Results:

Blueberry and chitosan significantly decreased liver arginase activity and ornithine levelsand and increased nitric oxide levels. Glutathione levels were remarkably increased by chitosan and blueberry treatments.

Conclusion:

The results of the present study indicate that blueberry and chitosan effectively protected against the acetaminophen-induced hepatotoxicity. The hepatoprotective effect afforded by blueberry and chitosan can be attributed to its antioxidant and anti-inflammatory activities.

The postoperative management of pain from intracranial surgery in pediatric neurosurgical patients

Pain following intracranial surgery has historically been undertreated because of the concern that opioids, the analgesics most commonly used to treat moderate-to-severe pain, will interfere with the neurologic examination and adversely affect postoperative outcome. Over the past decade, accumulating evidence, primarily in adult patients, has revealed that moderate-to-severe pain is common in neurosurgical patients following surgery. Using the neurophysiology of pain as a blueprint, we have highlighted some of the drugs and drug families used in multimodal pain management. This analgesic method minimizes opioid-induced adverse side effects by maximizing pain control with smaller doses of opioids supplemented with neural blockade and nonopioid analgesics, such nonsteroidal antiinflammatory drugs, local anesthetics, corticosteroids, N-methyl-D-aspartate (NMDA) antagonists, α2 -adrenergic agonists, and/or anticonvulsants (gabapentin and pregabalin).

An improved model of heat-induced hyperalgesia--repetitive phasic heat pain causing primary hyperalgesia to heat and secondary hyperalgesia to pinprick and light touch

This study tested a modified experimental model of heat-induced hyperalgesia, which improves the efficacy to induce primary and secondary hyperalgesia and the efficacy-to-safety ratio reducing the risk of tissue damage seen in other heat pain models. Quantitative sensory testing was done in eighteen healthy volunteers before and after repetitive heat pain stimuli (60 stimuli of 48°C for 6 s) to assess the impact of repetitive heat on somatosensory function in conditioned skin (primary hyperalgesia area) and in adjacent skin (secondary hyperalgesia area) as compared to an unconditioned mirror image control site. Additionally, areas of flare and secondary hyperalgesia were mapped, and time course of hyperalgesia determined. After repetitive heat pain conditioning we found significant primary hyperalgesia to heat, and primary and secondary hyperalgesia to pinprick and to light touch (dynamic mechanical allodynia). Acetaminophen (800 mg) reduced pain to heat or pinpricks only marginally by 11% and 8%, respectively (n.s.), and had no effect on heat hyperalgesia. In contrast, the areas of flare (−31%) and in particular of secondary hyperalgesia (−59%) as well as the magnitude of hyperalgesia (−59%) were significantly reduced (all p<0.001). Thus, repetitive heat pain induces significant peripheral sensitization (primary hyperalgesia to heat) and central sensitization (punctate hyperalgesia and dynamic mechanical allodynia). These findings are relevant to further studies using this model of experimental heat pain as it combines pronounced peripheral and central sensitization, which makes a convenient model for combined pharmacological testing of analgesia and anti-hyperalgesia mechanisms related to thermal and mechanical input.

Paracetamol: a focus for the general pediatrician

Paracetamol (acetaminophen) is one of the most popular and widely used drugs for the treatment of pain and fever in children. This drug has multiple mechanisms of action, but its pharmacodynamic is still not well known. The central nervous system is the main site of action and it mirrors the paracetamol effect compartment. The recommended dosages and routes of administration should be different whether paracetamol is used for the treatment of pain or fever. For example, the rectal route, while being efficacious for the treatment of fever, should be avoided in pain management. Paracetamol is a safe drug, but some clinical conditions and concomitant drugs, which are frequent in clinical practice, may increase the risk of paracetamol toxicity. Therefore, it is important to optimize its administration to avoid overdoses and maximize its effect. The principal mediator of the paracetamol toxicity is the N-acetyl-p-benzo-quinone imine (NAPQI), a toxic product of the paracetamol metabolism, which could bind cysteine groups on proteins forming paracetamol-protein adduct in the liver.

CONCLUSION

Although frequently prescribed, the concept of "effect compartment concentration" and the possible co-factors that could cause toxicity at recommended doses are not familiar to all pediatricians and general practitioners. We reviewed the literature concerning paracetamol mechanisms of action, we highlighted some relevant pharmacodynamic concepts for clinical practice, and we summarized the possible risk factors for toxicity at therapeutic dosages.

The effect of sunitinib on the plasma exposure of intravenous paracetamol and its major metabolite: paracetamol glucuronide

The study aimed to examine the effect of sunitinib on the plasma exposure of intravenous paracetamol and its major metabolite, paracetamol glucuronide. Both drugs share metabolic pathways in the liver, and the drug interactions between sunitinib and paracetamol administered in higher doses were reported. These interactions resulted in hepatotoxicity. The adult New Zealand male rabbits were divided into three groups (6 animals each): rabbits receiving sunitinib and paracetamol (SUN + PC), rabbits receiving sunitinib (SUN), and a control group receiving paracetamol (PC). Sunitinib was administered orally (25 mg) and paracetamol was administrated intravenously (35 mg/kg). Blood samples for sunitinib and SU12662 assays were collected up to 96 h after drug administration and for paracetamol and paracetamol glucuronide up to 300 min after drug administration. Aspartate aminotransferase (AST), alanine aminotransferase (ALT), and bilirubin were analysed before and after drug administration. A number of pharmacokinetic parameters were analysed. There were no differences in the levels of AST, ALT, and bilirubin among the groups at either time point. Significantly higher values of AUC_0–t, AUC_0–∞, and C_max and lower clearance and volume of distribution of paracetamol were observed in group PC vs. group SUN + PC (p < 0.01). The maximum plasma concentration of paracetamol glucuronide tended to be higher in group PC 213.27 μg/mL (90 % CI 1.06, 1.25; p = 0.0267). Statistically significant differences were revealed for paracetamol glucuronide mean residence time (MRT); MRT was higher in group SUN + PC than in group PC (p = 0.0375). The mean t_max of paracetamol glucuronide was similar in both groups: SUN + PC and group PC (15 and 20 min, respectively). The mean t_max of sunitinib was different in groups SUN + PC and SUN (10.0 and 7.0, respectively; p = 0.0134). At the studied doses, neither of the drugs, whether administered alone or together, had hepatotoxic effects. The present study was not able to confirm that sunitinib, administered at low doses in conjunction with paracetamol, displays a hepatoprotective effect. Significant differences were observed in some pharmacokinetic parameters of paracetamol.

Experimental and theoretical study of p-nitroacetanilide

The spectroscopic properties of the p-nitroacetanilide (PNA) were examined by FT-IR, FT-Raman and UV-Vis techniques. FT-IR and FT-Raman spectra in solid state were observed in the region 4000-400 cm(-1) and 3500-100 cm(-1), respectively. The UV-Vis absorption spectrum of the compound that dissolved in ethanol was recorded in the range of 200-400 nm. The structural and spectroscopic data of the molecule in the ground state were calculated by using density functional theory (DFT) employing B3LYP methods with the 6-31G(d,p) and 6-311+G(d,p) basis sets. The geometry of the molecule was fully optimized, vibrational spectra were calculated and fundamental vibrations were assigned on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. Thermodynamic properties like entropy, heat capacity and enthalpy have been calculated for the molecule. HOMO-LUMO energy gap has been calculated. The intramolecular contacts have been interpreted using natural bond orbital (NBO) and natural localized molecular orbital (NLMO) analysis. Important non-linear optical (NLO) properties such as electric dipole moment and first hyperpolarizability have been computed using B3LYP quantum chemical calculation.

Arsenic reduces the antipyretic activity of paracetamol in rats: modulation of brain COX-2 activity and CB₁ receptor expression

We examined whether subacute arsenic exposure can reduce paracetamol-mediated antipyretic activity by affecting COX pathway and cannabinoid CB1 receptor regulation. Rats were preexposed to elemental arsenic (4 ppm) as sodium arsenite through drinking water for 28 days. Next day pyrexia was induced with lipopolysaccharide and paracetamol's (200 mg/kg, oral) antipyretic activity was assessed. The activities of COX-1 and COX-2, the levels of PGE₂, TNF-α and IL-1β and expression of CB₁ receptors were assessed in brain. Arsenic inhibited paracetamol-mediated antipyretic activity. COX-1 activity was not affected by any treatments. Paracetamol decreased COX-2 activity, levels of PGE₂, TNF-α and IL-1β and caused up-regulation of CB1 receptors. Arsenic caused opposite effects on these parameters. In the arsenic-preexposed rats, paracetamol-mediated effects were attenuated, while CB₁ receptor up-regulation was reversed to down-regulation. Results suggest that elevated COX-2 activity and reduced CB₁ expression could be involved in the arsenic-mediated attenuation of the antipyretic activity of paracetamol.

Comparison of intravenous ketorolac with or without paracetamol in postoperative pain control following ambulatory surgery

OBJECTIVE

The aim of this randomized, patient-blinded study was to compare efficacy and safety of oral paracetamol plus intra-venous (i.v.) ketorolac with i.v. ketorolac alone after ambulatory uterine evacuation.

RESEARCH DESIGN AND METHODS

Women were randomly assigned to receive either oral paracetamol (1 g), in a melt-in-the mouth, without-water formulation plus ketorolac (30 mg i.v. once daily (o.d.)) or ketorolac (30 mg i.v. o.d.) as monotherapy. The mean duration of uterine evacuation was 11 minutes in the paracetamol + ketorolac group and 13 minutes in the ketorolac-only group. Paracetamol was administered 15 minutes before surgery, on discharge from hospital (mean 6 hours after surgery) and in the morning the day after surgery, while ketorolac was administered at the end of the surgical intervention.

MAIN OUTCOME MEASURES

The numeric rating scale (NRS) was used by patients to rate their pain on an 11 point scale.

RESULTS

Overall, 60 women received paracetamol plus ketorolac (group 1) and 60 ketorolac alone (group 2). There were significant differences in pain levels (NRS 0.92 and 2.08; p < 0.01) at T0 (when patients left the operating room 30 minutes after the end of surgery). At T1 (before discharge from hospital but before the next administration of paracetamol) there were no significant differences between NRS scores in the two groups (3.7 vs. 3.5, respectively, p = 0.3453). At T2 (in the morning after surgery; data collected by phone interview), following administration of the next dose of paracetamol, significant differences in pain scores were recorded (1.58 vs. 1.98; p = 0.01). Only a case of dizziness was reported in the paracetamol + ketorolac group, and no other unexpected adverse events were recorded.

CONCLUSION

Despite the small sample size and the monocentric nature of the study being taken into account, this study suggests, for the first time to our knowledge, that oral paracetamol t.i.d. in combination with i.v. ketorolac o.d. is effective and well tolerated in the control of postoperative pain after ambulatory uterine evacuation.

Prodrugs: a challenge for the drug development

It is estimated that about 10% of the drugs approved worldwide can be classified as prodrugs. Prodrugs, which have no or poor biological activity, are chemically modified versions of a pharmacologically active agent, which must undergo transformation in vivo to release the active drug. They are designed in order to improve the physicochemical, biopharmaceutical and/or pharmacokinetic properties of pharmacologically potent compounds. This article describes the basic functional groups that are amenable to prodrug design, and highlights the major applications of the prodrug strategy, including the ability to improve oral absorption and aqueous solubility, increase lipophilicity, enhance active transport, as well as achieve site-selective delivery. Special emphasis is given to the role of the prodrug concept in the design of new anticancer therapies, including antibody-directed enzyme prodrug therapy (ADEPT) and gene-directed enzyme prodrug therapy (GDEPT).

Effect of naproxen and acetaminophen on blood pressure lowering by ramipril, valsartan and aliskiren in hypertensive patients

BACKGROUND

Non-steroidal anti-inflammatory drugs (NSAIDs) are frequently used for reducing pain and other symptoms in osteoarthritis (OA). NSAIDs have been associated with an increase in blood pressure (BP) in both normotensive and hypertensive individuals and a blunting effect on various anti-hypertensive medications. Acetaminophen effects on anti-hypertensive treatment, instead, are still a matter of debate.

OBJECTIVES

To assess the effect of naproxen versus acetaminophen on ramipril, valsartan and aliskiren therapy in hypertensive patients with OA in a double-blind, cross-over study, by measuring clinic, ambulatory BP and heart rate (HR).

RESULTS

One hundred seventy four patients were randomly treated with ramipril, valsartan or aliskiren for 8 weeks and 135 patients with normalized BP were randomized to receive naproxen or acetaminophen for 2 weeks. Naproxen significantly increased clinic and ambulatory systolic/diastolic BP (SBP/DBP) values in patients treated with ramipril (p < 0.01) or valsartan (p < 0.05), but did not affect aliskiren effects. Also acetaminophen slightly but significantly affected clinic and ambulatory SBP/DBP in all three groups and, surprisingly, it also produced a slight increase in HR (+3.1, +3.3 and +3.4 b/min day-time HR values, for ramipril, valsartan and aliskiren, respectively; p < 0.05).

CONCLUSIONS

Both naproxen and acetaminophen can affect anti-hypertensive therapy with ramipril, valsartan or aliskiren with a different extent. When acetaminophen is chosen for OA management in subjects with hypertension, patients should be evaluated as carefully as when traditional NSAIDs are given.

The modern pharmacology of paracetamol: therapeutic actions, mechanism of action, metabolism, toxicity and recent pharmacological findings

Paracetamol is used worldwide for its analgesic and antipyretic actions. It has a spectrum of action similar to that of NSAIDs and resembles particularly the COX-2 selective inhibitors. Paracetamol is, on average, a weaker analgesic than NSAIDs or COX-2 selective inhibitors but is often preferred because of its better tolerance. Despite the similarities to NSAIDs, the mode of action of paracetamol has been uncertain, but it is now generally accepted that it inhibits COX-1 and COX-2 through metabolism by the peroxidase function of these isoenzymes. This results in inhibition of phenoxyl radical formation from a critical tyrosine residue essential for the cyclooxygenase activity of COX-1 and COX-2 and prostaglandin (PG) synthesis. Paracetamol shows selectivity for inhibition of the synthesis of PGs and related factors when low levels of arachidonic acid and peroxides are available but conversely, it has little activity at substantial levels of arachidonic acid and peroxides. The result is that paracetamol does not suppress the severe inflammation of rheumatoid arthritis and acute gout but does inhibit the lesser inflammation resulting from extraction of teeth and is also active in a variety of inflammatory tests in experimental animals. Paracetamol often appears to have COX-2 selectivity. The apparent COX-2 selectivity of action of paracetamol is shown by its poor anti-platelet activity and good gastrointestinal tolerance. Unlike both non-selective NSAIDs and selective COX-2 inhibitors, paracetamol inhibits other peroxidase enzymes including myeloperoxidase. Inhibition of myeloperoxidase involves paracetamol oxidation and concomitant decreased formation of halogenating oxidants (e.g. hypochlorous acid, hypobromous acid) that may be associated with multiple inflammatory pathologies including atherosclerosis and rheumatic diseases. Paracetamol may, therefore, slow the development of these diseases. Paracetamol, NSAIDs and selective COX-2 inhibitors all have central and peripheral effects. As is the case with the NSAIDs, including the selective COX-2 inhibitors, the analgesic effects of paracetamol are reduced by inhibitors of many endogenous neurotransmitter systems including serotonergic, opioid and cannabinoid systems. There is considerable debate about the hepatotoxicity of therapeutic doses of paracetamol. Much of the toxicity may result from overuse of combinations of paracetamol with opioids which are widely used, particularly in USA.

Acetaminophen prevents oxidative burst and delays apoptosis in human neutrophils

Acetaminophen is a frequently prescribed over-the-counter drug to reduce fever and pain in the event of inflammatory process. As neutrophils are relevant cells in inflammatory processes, the putative interaction of acetaminophen with these cells, if present, would be of paramount importance. The present study was undertaken to evaluate the effect of acetaminophen in human neutrophils' oxidative burst and lifespan in vitro. The obtained results demonstrate that acetaminophen efficiently modulates neutrophils' oxidative burst in phorbol myristate acetate-activated neutrophils, in a concentration-dependent manner, at in vivo relevant concentrations. It was clearly demonstrated that acetaminophen is a strong scavenger of HOCl and H2O2, which probably contributed to the effect observed in neutrophils. Acetaminophen also induced the depletion of glutathione in stimulated neutrophils, suggesting its transformation into a reactive intermediate. Obtained results further revealed that acetaminophen affects programmed cell death of human neutrophils, resulting in a delay of previously stimulated neutrophils-mediated apoptosis. Overall, our data suggested that acetaminophen has considerable potential to be included in anti-inflammatory therapeutic strategies, by preventing biological damage induced by an excessive production of reactive species generated in activated neutrophils and by extending the lifespan of neutrophils, favoring the elimination of pathogens, thus contributing to tissue healing and resolution of inflammation.

Prenatal and perinatal analgesic exposure and autism: an ecological link

BACKGROUND

Autism and Autism Spectrum Disorder (ASD) are complex neurodevelopmental disorders. Susceptibility is believed to be the interaction of genetic heritability and environmental factors. The synchronous rises in autism/ASD prevalence and paracetamol (acetaminophen) use, as well as biologic plausibility have led to the hypothesis that paracetamol exposure may increase autism/ASD risk.

METHODS

To explore the relationship of antenatal paracetamol exposure to ASD, population weighted average autism prevalence rates and paracetamol usage rates were compared. To explore the relationship of early neonatal paracetamol exposure to autism/ASD, population weighted average male autism prevalence rates for all available countries and U.S. states were compared to male circumcision rates - a procedure for which paracetamol has been widely prescribed since the mid-1990s. Prevalence studies were extracted from the U.S. Centers for Disease Control and Prevention Summary of Autism/ASD Prevalence Studies database. Maternal paracetamol usage and circumcision rates were identified by searches on Pub Med.

RESULTS

Using all available country-level data (n = 8) for the period 1984 to 2005, prenatal use of paracetamol was correlated with autism/ASD prevalence (r = 0.80). For studies including boys born after 1995, there was a strong correlation between country-level (n = 9) autism/ASD prevalence in males and a country's circumcision rate (r = 0.98). A very similar pattern was seen among U.S. states and when comparing the 3 main racial/ethnic groups in the U.S. The country-level correlation between autism/ASD prevalence in males and paracetamol was considerably weaker before 1995 when the drug became widely used during circumcision.

CONCLUSIONS

This ecological analysis identified country-level correlations between indicators of prenatal and perinatal paracetamol exposure and autism/ASD. State level correlation was also identified for the indicator of perinatal paracetamol exposure and autism/ASD. Like all ecological analyses, these data cannot provide strong evidence of causality. However, biologic plausibility is provided by a growing body of experimental and clinical evidence linking paracetamol metabolism to pathways shown to be important in autism and related developmental abnormalities. Taken together, these ecological findings and mechanistic evidence suggest the need for formal study of the role of paracetamol in autism.

The Common Pain of Surrealism and Death

The meaning-maintenance model posits that any violation of expectations leads to an affective experience that motivates compensatory affirmation. We explore whether the neural mechanism that responds to meaning threats can be inhibited by acetaminophen, in the same way that acetaminophen inhibits physical pain or the distress caused by social rejection. In two studies, participants received either acetaminophen or a placebo and were provided with either an unsettling experience or a control experience. In Study 1, participants wrote about either their death or a control topic. In Study 2, participants watched either a surrealist film clip or a control film clip. In both studies, participants in the meaning-threat condition who had taken a placebo showed typical compensatory affirmations by becoming more punitive toward lawbreakers, whereas those who had taken acetaminophen, and those in the control conditions, did not.

Is fever a predictive factor in the autism spectrum disorders?

Autism spectrum disorders (ASD) display such a marked increase in recent decades that researchers speak of "epidemic outbreak" of the disease. Although the diagnostic framework has been expanded and thus more disorders now fall within the autistic spectrum, no one disputes the increased incidence of autism in modern societies, making it a major public health problem. On the other hand, heterogeneity is a major feature of the disorder, both in terms of the etiopathogenesis as well as to the phenotypic expression, natural history and evolution. Consequently, there is considerable research interest in determining factors which are etiopathogenetically, prognostically, preventively or/and therapeutically associated with the disorder. Literature data indicate that probably there are differences in susceptibility to various infections between normal and autistic children. In addition, some autistic children show improvement in the characteristics of their autistic behavior during febrile incident and repression of fever (through antipyretics) might be associated with the onset of autistic disorder. Since fever has been associated with mental illness since the time of Hippocrates already and the presence of fever is associated with a favorable outcome in various pathologic conditions, it is assumed that there are probably two subgroups of autistic children: those who have the possibility to develop acute febrile incidents and those who develop acute incidents without fever. If this is the case, it is important to know whether there are differences between the two subgroups in various biological markers (cytokines/chemokines, autoantibodies), neuroimaging findings, personal and family history of these children (use of drugs, vaccinations, history of autoimmunity, etc.) and, if the first subgroup consists of autistic people of higher functionality and better outcome, or not. If such a classification is real, is there a possibility for the fever to be used as a predictor of the autistic disorder outcome and of whether that person will achieve an acceptable level of functionality in the future? If there are positive answers to these questions, are autistic children, who develop fever, at a very critical stage in evolutionary terms, where it is very important not to lose the defense mechanism of fever development and thus mast use the fever repression methods (antipyretic drugs for example) with caution and chariness? If it is confirmed that autistic children with high fevers are of higher functionality, it is possible for preventive intervention programs to be developed where children are exposed to the least possible chemical drugs intervention (antipyretics, antibiotics, etc.) or even selective vaccination. Further experimental, epidemiological and clinical studies are necessary to investigate the above.

Acetaminophen, pesticide, and diethylhexyl phthalate metabolites, anandamide, and fatty acids in deciduous molars: potential biomarkers of perinatal exposure

The developing fetus is particularly vulnerable to adverse effects from pharmaceutical and exogenous chemical exposure. Deciduous teeth primarily form over specific periods from the second trimester in utero through the months after birth. We hypothesized that organic chemicals or their metabolites circulating in the bloodstream may sorb into forming dental tissues and remain stored in the tooth thereafter. Our aims were to devise analytical and preparation methods for potentially toxic or beneficial organic chemicals or metabolites in deciduous teeth and to estimate their detection frequencies. The analgesic acetaminophen was stored at greater concentration in a child's second molar than a first molar, consistent with intake, suggesting that acetaminophen concentration in molars may be a biomarker of acetaminophen exposure during molar formation. Chemicals detected by liquid chromatography/tandem mass spectrometry in molars of 21 typically developing children include the endocannabinoid anandamide (86% of children), acetaminophen (43%), and specific metabolites mono-2-ethylhexyl phthalate (MEHP, of plasticizer di-2-ethylhexyl phthalate, 29%), 3,5,6-trichloro-2-pyridinol (TCPy, of organophosphate (OP) insecticide chlorpyrifos, 10%), and 2-isopropyl-6-methyl-4-pyrimidinol (IMPy, of OP insecticide diazinon, 10%). None of these chemicals has previously been detected in human teeth. Molars from the two oldest subjects contained the largest concentrations of MEHP, TCPy, and IMPy. Potentially protective fatty acids detected by gas chromatography/mass spectrometry after derivatization include docosahexaenoic (19%), arachidonic (100%), and linoleic (100%). Validation studies are necessary to verify that each detected chemical in molars provides a biomarker of perinatal exposure.

Intraocular pressure-lowering effect of oral paracetamol and its in vitro corneal penetration properties

BACKGROUND

Several studies have confirmed the ability of cannabinoids to reduce intraocular pressure. Experimental data recently demonstrated unequivocally that the analgesic effect of paracetamol is due to its indirect action on cannabinoid receptors. The question then arises as to whether paracetamol can reduce intraocular pressure via its effect on intraocular cannabinoid receptors.

METHODS

A 2-week, prospective, randomized, controlled, single-center, parallel-group pilot study was carried out to determine the efficacy and safety of paracetamol 1 g orally administered every 6 hours in adult patients with primary or secondary open angle glaucoma as compared with topical levobunolol 0.5% twice a day. Patient well-being was closely monitored throughout the study and focused on hepatic safety in accordance with Drug-Induced Liver Injury Network criteria. The in vitro diffusion kinetics of acetaminophen in a phosphate-buffered solution in rabbit and human corneas was also investigated, with the view to a topical application.

RESULTS

Eighteen adult patients were enrolled in the study, with nine in the topical levobunolol group and nine in the oral paracetamol group. In the levobunolol group, the mean reduction in intraocular pressure at day 7 was 7.5 mmHg (P < 0.008) and at day 14 was 9.1 mmHg (P < 0.005), from a mean baseline intraocular pressure of 29.6 mmHg. The corresponding figures for the paracetamol group were 8.8 mmHg (P < 0.0004) at day 7 and 6.5 mmHg (P < 0.004) at day 14, from a mean baseline intraocular pressure of 29.4 mmHg. Both study regimens were well tolerated. No serious treatment-related adverse events were reported in either of the treatment groups. Liver function tests, systolic/diastolic blood pressure, or heart rate remained unchanged in both groups during the 2 weeks of the study. In the laboratory study, paracetamol 1 mg/mL in phosphate-buffered solution (pH 7.4) showed acceptable flux rates. Steady-state levels were achieved within 12 hours, thus confirming that paracetamol penetrates the cornea well.

CONCLUSION

Paracetamol 1 g taken orally every 6 hours reduced open angle glaucoma and/or angle recession glaucoma in both groups of patients, in a way comparable with that achieved by a topical beta-adrenergic receptor antagonist.

A novel paracetamol 1,000 mg sustained release formulation vs conventional paracetamol 500 mg formulation in patients with fever and pain: a randomized noninferiority trial

OBJECTIVE

To compare the efficacy and safety of newly developed paracetamol 1,000 mg sustained release (SR) tablets (test product) with conventional paracetamol 500 mg tablets (reference product) in patients with fever and pain.

DESIGN

An open label, multicentric, comparative, randomized, noninferiority trial.

METHODOLOGY

Eligible patient, as per predefined inclusion and exclusion criteria, were randomized to receive either one tablet of test product twice daily or one tablet of reference product four times a day for 3 consecutive days. Primary efficacy parameter (an antipyretic activity) was measured through recording changes in body temperature while secondary efficacy parameter (an analgesic activity) was measured by recording changes in visual analog scale (VAS) from the baseline. Safety assessment was done by recording adverse drug reactions occurred during treatment period. Analysis of variance was used for the statistical evaluation of data.

RESULTS

Of 500 randomized patients, 249 were received paracetamol 1,000 mg SR tablets (Group-I), and 247 were received conventional paracetamol 500 mg tablets (Group-II). Group-I reported temperature reduction from 101.35 ± 1.23°F to 98.80 ± 0.72°F while temperature reduction in Group-II was from 101.42 ± 1.33°F to 98.9 ± 0.85°F. Group-I reported reduction in mean VAS was from 6.16 ± 2.37 to 1.44 ± 1.70 in comparison to Group-II from 5.97 ± 2.45 to 1.38 ± 1.78. No significant adverse reactions were observed in either group.

CONCLUSION

Both the formulations of paracetamol were clinically and statically equivalent. Paracetamol 1,000 mg SR formulation is noninferior to conventional paracetamol 500 mg tablets.

Ultrasound-guided transversus abdominal plane block with multimodal analgesia for pain management after total abdominal hysterectomy

BACKGROUND

Transversus abdominis plane (TAP) block has been shown to provide pain relief after abdominal procedures. However, TAP block combined with multimodal analgesia technique have not been assessed in a randomized controlled trial. This randomized, controlled, observer-blinded study was designed to evaluate the analgesic efficacy of bilateral ultrasound-guided TAP blocks with or without acetaminophen and non-steroidal anti-inflammatory drug (NSAID) combination.

METHODS

Patients undergoing total abdominal hysterectomy were randomized to one of three groups. Group 1 (n = 25) received a TAP block and ketorolac 30 mg, IV at the end of surgery and then ketorolac plus paracetamol 650 mg, orally, every 6 h for 24 h. Group 2 (n = 24) received only TAP block at the end of surgery. Group 3 (n = 25) received ketorolac 30 mg, IV at the end of surgery and then ketorolac plus paracetamol 650 mg, orally, every 6 h for 24 h. All patients received IV-PCA morphine for 24-h, postoperatively. All patients received a standardized general anaesthetic technique and dexamethasone 4 mg and ondansetron 4 mg, IV for antiemetic prophylaxis.

RESULTS

There were no statistically significant differences in pain at rest between the groups. However, the pain on coughing (dynamic pain) in Group 1 was significantly less variable, compared with the other two groups (P = 0.012). Opioid consumption and occurrences of nausea, vomiting, and rescue antiemetic were similar in three the groups.

CONCLUSIONS

The combination of TAP block and acetaminophen and NSAID provided less variability in dynamic pain compared with either treatment alone.

Nonsteroidal antiinflammatory drugs, acetaminophen, and hypertension

Selective and non-selective non-steroidal anti-inflammatory drugs (NSAIDs) as well as acetaminophen belong to the most widely prescribed therapeutic agents worldwide. Their efficacy in pain relief notwithstanding, the use of NSAIDs is associated with an increased cardiovascular risk, which can be partly attributed to their blood pressure raising potential. Adequately powered placebo-controlled trials specifically evaluating the cardiovascular safety of NSAIDs vs. selective COX inhibitors are currently underway. This review summarizes the current knowledge on the cardiovascular effects of NSAIDs and acetaminophen, and their potential clinical consequences.

The effect of paracetamol and tropisetron on pain: experimental studies and a review of published data

Experimental studies suggest that paracetamol-induced analgesia is mediated via central serotonergic pathways and attenuated by 5-HT3-antagonists. However, clinical studies do not support this, and 5-HT3-antagonists are expected to reduce pain by blocking the descending pronociceptive pathway. The current project tested whether tropisetron attenuates analgesia by paracetamol. Two randomized, double-blind, crossover studies with 18 healthy male volunteers in each were performed. Pain stimuli were cold water immersion (cold pressor test), contact heat pain (study 1) and electrical stimulation (study 2). In both studies, tropisetron 5 mg i.v. or saline was administered, followed by paracetamol 2 g i.v. 30 min. later. Individual changes in heat and cold pain intensity, cold pain tolerance and unpleasantness were recorded. The same thresholds were also expressed as scores (% of the individual score at baseline). Additionally, previously published findings on the effects of paracetamol and its interaction with 5HT3-antagonists in human experimental pain models were reviewed. After calculation of the sensory and pain scores (%), tropisetron seemed to amplify the analgesic action of paracetamol. Paracetamol 2 g i.v. did not show any statistically significant analgesia in thermal tests (study 1), or differences in sensory, pain detection or moderate pain thresholds of the electrical stimulus (study 2). As paracetamol did not have a measurable analgesic effect in these tests, no conclusions can be drawn about the interaction between paracetamol and tropisetron. However, tropisetron may have an analgesic effect of its own. Clinicians should not avoid using these drugs together, unless larger clinical studies indicate otherwise.

The use of different analgesics in orthodontic tooth movements

OBJECTIVE

To provide a semi-quantitative assessment of the effect of different analgesics (celecoxib, ketorolac, and paracetamol) on tooth movement and bone resorption using immunohistochemical staining of matrix metalloproteinase-13 (MMP-13).

MATERIALS AND METHODS

Forty white male rats (12-weeks old; body weight: 230-250 g) were divided into four groups (10 rats each) and were given the treatment once a day for 2 consecutive months. Group A (control group) rats were given the reverse osmosis water; group B rats were given 10 mg/kg celecoxib; group C rats were given 3 mg/kg ketorolac; and group D rats were given 150 mg/kg paracetamol. A precalibrated closed Sentalloy coil spring was placed inside each rat mouth to deliver a constant force of 50 cN. The magnitude of tooth movement was measured intraorally. After 2 months, the rats were sacrificed, and the sections were mounted on L-polylysine-coated glass slides. Slides from each specimen were stained with hematoxylin and eosin, and others were stained with MMP-13. Data were analyzed with the one-way analysis of variance (ANOVA).

RESULTS

Celecoxib, ketorolac, and paracetamol groups showed tooth movement of 1.81 ± 0.43 mm, 1.13 ± 0.28 mm, and 1.08 ± 0.27 mm, respectively. The mean number of MMP-13-positive osteoclasts was highest in celecoxib-treated group followed by the control group and was decreased in the ketorolac and paracetamol groups. Comparing all groups to the control revealed significant differences (P < .05).

CONCLUSION

Administration of celecoxib did not reduce bone resorption or interfere with tooth movement in rats compared to other analgesics tested (ketorolac and paracetamol).

Role of intravenous acetaminophen in postoperative pain management

SUMMARY The need to safely treat the postoperative pain of patients is apparent. Opioids, although effective, have multiple morbidities associated with their use. A multimodal approach to postoperative pain management can serve to minimize the undesirable effects of opioids. Intravenous acetaminophen (paracetamol) has recently become available in the USA where many practitioners are not familiar with this drug. This article reviews the history, pharmacology and clinical uses of intravenous acetaminophen in the treatment of perioperative pain.

Management of chronic pain in the rheumatic diseases with insights for the clinician

Pain that accompanies musculoskeletal conditions should be regarded as an illness entity in its own right and deserves treatment in parallel with the management of the underlying condition. Recent understanding of the pathophysiology of rheumatic pain invokes interplay of the nociceptive mechanisms driven by local tissue factors and the neurogenic responses that sustain chronic pain. In line with other pain conditions, ideal treatment of rheumatic pain should be through a multimodal approach, integrating nonpharmacologic as well as pharmacologic treatments. In the light of this new concept of pain mechanisms, future pharmacologic treatment options may encompass a wider scope than the use of traditional analgesics and nonsteroidal anti-inflammatory drugs. There is currently limited experience for use of pharmacologic treatments that act primarily on neurogenic mechanisms in rheumatic conditions. Drug combination studies are lacking, but this strategy seems clinically reasonable to allow for an approach to treating pain from different mechanistic perspectives. An added advantage would be the opportunity to use lower doses of individual drugs and thereby reduce the side effect profile. Ideal pain management must also include attention to the important co-associates of pain such as effects on sleep, mood and energy, which all have an impact on the global burden of suffering. Although complete relief of pain is still an unrealistic objective, reasonable outcome goals for symptom relief should be accompanied with an improvement in function.

Acetaminophen differentially enhances social behavior and cortical cannabinoid levels in inbred mice

Supratherapeutic doses of the analgesic acetaminophen (paracetomol) are reported to promote social behavior in Swiss mice. However, we hypothesized that it might not promote sociability in other strains due to cannabinoid CB(1) receptor-mediated inhibition of serotonin (5-HT) transmission in the frontal cortex. We examined the effects of acetaminophen on social and repetitive behaviors in comparison to a cannabinoid agonist, WIN 55,212-2, in two strains of socially-deficient mice, BTBR and 129S1/SvImJ (129S). Acetaminophen (100mg/kg) enhanced social interactions in BTBR, and social novelty preference and marble burying in 129S at serum levels of ≥70 ng/ml. Following acetaminophen injection or sociability testing, anandamide (AEA) increased in BTBR frontal cortex, while behavior testing increased 2-arachidonyl glycerol (2-AG) levels in 129S frontal cortex. In contrast, WIN 55,212-2 (0.1mg/kg) did not enhance sociability. Further, we expected CB(1)-deficient (+/-) mice to be less social than wild-type, but instead found similar sociability. Given strain differences in endocannabinoid response to acetaminophen, we compared cortical CB(1) and 5-HT(1A) receptor density and function relative to sociable C57BL/6 mice. CB(1) receptor saturation binding (Bmax=958±117 fmol/mg protein), and affinity for [(3)H] CP55,940 (K(D)=3±0.8 nM) was similar in frontal cortex among strains. CP55,940-stimulated [(35)S] GTPγS binding in cingulate cortex was 136±12, 156±22, and 75±9% above basal in BTBR, 129S and C57BL/6 mice. The acetaminophen metabolite para-aminophenol (1 μM) failed to stimulate [(35)S] GTPγS binding. Hence, it appears that other indirect actions of acetaminophen, including 5-HT receptor agonism, may underlie its sociability promoting properties outweighing any CB(1) mediated suppression by locally-elevated endocannabinoids in these mice.

Extended-release tramadol/paracetamol in moderate-to-severe pain: a randomized, placebo-controlled study in patients with acute low back pain

OBJECTIVE

Combinations of oral analgesics may offer several potential benefits compared with an individual agent. The objective of this study was to investigate the efficacy and safety of an extended-release, twice-daily fixed combination of 75 mg tramadol/650 mg paracetamol (DDS-06C) in the treatment of moderate-to-severe pain, using acute low back pain as a model.

RESEARCH DESIGN AND METHODS

In this phase III study, 277 patients with moderate-to-severe acute low back pain were randomized to 1-2 tablets of DDS-06C or placebo every 10-12 h for 2.5 days during the double-blind phase. Following the double-blind phase, patients had the option to continue for a 2.5-day open-label phase.

CLINICAL TRIAL REGISTRATION

Clinicaltrials.gov (Identifier: NCT00643383)

MAIN OUTCOME MEASURES

The primary end point was the sum of pain intensity differences (SPID) over the 50-h double-blind phase (SPID50). Secondary end points included total pain relief score over the 50-h double-blind phase (TOTPAR50), patient's global impression of medication, and SPID over the first 4 h.

RESULTS

A statistically significant (p = 0.038) greater decrease in pain intensity was observed in the DDS-06C group (median SPID50: -6.0) versus placebo (median SPID50: -4.0). Greater pain relief was also observed in patients randomized to DDS-06C: the median TOTPAR50 was 13.0 for the DDS-06C group and 11.0 for placebo (p = 0.026). DDS-06C demonstrated statistically significant superior efficacy compared with placebo for the majority of the other secondary end points. Overall, 38% of patients treated with DDS-06C experienced at least one adverse event; the intensity was mild-to-moderate in 81% of cases. The most commonly reported adverse events (>5% of patients receiving DDS-06C) were nausea, dizziness, vomiting, and somnolence.

CONCLUSIONS

Using acute low back pain, a model with a high degree of heterogeneity and intrinsic variability, DDS-06C was superior to placebo on measures of pain intensity and relief, and was well-tolerated.

Combination Drug Therapy for Pain following Chronic Spinal Cord Injury

A number of mechanisms have been elucidated that maintain neuropathic pain due to spinal cord injury (SCI). While target-based therapeutics are being developed based on elucidation of these mechanisms, treatment for neuropathic SCI pain has not been entirely satisfactory due in part to the significant convergence of neurological and inflammatory processes that maintain the neuropathic pain state. Thus, a combination drug treatment strategy, wherein several pain-related mechanism are simultaneously engaged, could be more efficacious than treatment against individual mechanisms alone. Also, by engaging several targets at once, it may be possible to reduce the doses of the individual drugs, thereby minimizing the potential for adverse side effects. Positive preclinical and clinical studies have demonstrated improved efficacy of combination drug treatment over single drug treatment in neuropathic pain of peripheral origin, and perhaps such combinations could be utilized for neuropathic SCI pain. At the same time, there are mechanisms that distinguish SCI from peripheral neuropathic pain, so novel combination therapies will be needed.