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PubMed1987

Dose-dependent pharmacokinetics of acetaminophen: evidence of glutathione depletion in humans.

The time course of excretion of acetaminophen and its metabolites in urine was determined in eight healthy adults (seven men and one woman) who ingested 1 gm of the drug and collected timed urine samples for 24 hours. The mean time of peak excretion rate was 1.3 to 3.7 hours for acetaminophen, its glucuronide, sulfate, cysteine, mercapturate, and methoxy metabolites but 13.5 hours for methylthioacetaminophen. The mean half-life of acetaminophen was 3.1 hours and the mean half-life of the metabolites other than methylthioacetaminophen ranged from 4.1 to 5.7 hours. The half-life of methylthiometabolite could not be determined because of its very late peak time. In a second study the effect of dose on the clearance of acetaminophen was determined in nine healthy adult subjects (eight men and one woman) who received doses of 0.5 and 3 gm acetaminophen on separate occasions, separated by 4 to 10 days. The renal clearance of acetaminophen and the formation clearances of the sulfate, glutathione, and catechol metabolites were lower (by 38%, 41%, 35%, and 46%, respectively) at the higher dose. The renal clearance of acetaminophen sulfate and glucuronide conjugates were not different between doses. In a third study (10 men), 10 gm N-acetylcysteine was found to increase the formation clearance of the sulfate conjugate by 27% and that of the glutathione conjugate by 10%. The data suggest that the hepatic supply of reduced glutathione and 3'-phosphoadenosine 5'-phosphosulfate begins to be depleted over the range of 0.5 to 3 gm acetaminophen and that the depletion is overcome by the administration of N-acetylcysteine.

Acetaminophen↗
PubMedDate not supplied

The cost-effectiveness of acetaminophen, NSAIDs, and selective COX-2 inhibitors in the treatment of symptomatic knee osteoarthritis.

OBJECTIVE: The objective of this study was to conduct an economic evaluation of rofecoxib and celecoxib compared with high-dose acetaminophen or ibuprofen with and without misoprostol for patients with symptomatic knee osteoarthritis (OA). METHODS: A decision analysis model was designed over 6 months using two measures of effectiveness: 1) number of upper gastrointestinal (GI) adverse events averted; and 2) number of patients who achieved perceptible pain relief. Separate analyses were conducted for all patients and for those who did not respond to acetaminophen. Outcome probabilities were obtained from a comprehensive review of randomized controlled trials and observational studies. Costs were derived from actual resource utilization of OA patients. RESULTS: In terms of averting GI events, acetaminophen dominates the other options for an average risk patient population. For patients who did not respond to acetaminophen, rofecoxib had the lowest incremental cost-effectiveness ratio (ICER) per GI event avoided (32,000 US dollars) relative to ibuprofen. In terms of pain control, ibuprofen had an ICER of 610.77 US dollars per additional patient achieving minimal perceptible clinical improvement (MPCI) relative to acetaminophen, while rofecoxib had an ICER of 12,000 US dollars relative to ibuprofen. For patients who did not respond to acetaminophen and who are at high risk of developing an adverse GI event, rofecoxib dominates ibuprofen as the preferred alternative for both measures of effectiveness. One-way, two-way, and probabilistic sensitivity analyses established that these results were generally robust. CONCLUSIONS: Our results suggest that for average-risk knee OA patients, acetaminophen dominates the other therapies in terms of cost per GI event averted. In terms of pain relief, cost-effectiveness acceptability curves indicate that if one values pain relief below 275 US dollars per patient achieving MPCI, acetaminophen is the therapy most likely to be optimal; between 275 US dollars and 14,150 US dollars, ibuprofen is most likely to be optimal; and above 14,150 US dollars, rofecoxib is most likely to be optimal.

Acetaminophen↗
PubMed2002

Treatment of acetaminophen-induced hepatitis and fulminant hepatic failure with extracorporeal sorbent-based devices.

When a patient with acetaminophen overdose arrives in the emergency room more than 14 hours after ingestion, the value of N-acetylcysteine is unproven and patient mortality is at least 10%. Anecdotal case reports have indicated benefit of extracorporeal detoxification of these late-arriving patients with acetaminophen overdose. We identified 10 patients with serious acetaminophen overdose, 8 that arrived in the emergency room 16 to 44 hours after acetaminophen overdose with plasma levels predicting severe hepatic toxicity, and 2 that arrived in the emergency room 8 to 12 hours after overdose but with exceedingly high levels. All patients developed severe hepatitis (mean peak alanine aminotransferase, 4,052; mean peak protime, 25 seconds). At 16 to 68 hours after overdose, the patients were treated for 4 to 6 hours with the Liver Dialysis System (Hemocleanse Inc, W. Lafayette, IN), a single-access hemodiabsorption system indicated for treatment of serious drug overdose and for treatment of hepatic encephalopathy. Acetaminophen levels fell an average of 73% during treatment. Treatment was repeated 24 or 48 hours later if acetaminophen was still measurable in plasma. All 10 patients recovered intrinsic liver function and general health, with liver enzymes starting to normalize 24 hours after treatment, and were discharged 3 to 7 days after overdose. No patient required liver transplant. Because market introduction of Liver Dialysis, there have been 40 more patients with acetaminophen-induced hepatotoxicity treated with Liver Dialysis. All have recovered liver function without long-term sequelae. Though most of these patients with already established hepatic toxicity from acetaminophen would recover without extracorporeal blood therapy, treatment with the Liver Dialysis System should assure recovery from acute hepatic failure, and may shorten the clinical course of the illness.

Acetaminophen↗
PubMed2002

Role of CCR2 in macrophage migration into the liver during acetaminophen-induced hepatotoxicity in the mouse.

The biological effects of monocyte chemoattractant protein (MCP) 1 are mediated by binding to C-C chemokine receptor (CCR) 2. In the present studies, we used CCR2 knockout (CCR2-/-) mice to examine the role of MCP-1 in acetaminophen-induced macrophage accumulation in the liver, expression of inflammatory cytokines, and hepatotoxicity. We found that hepatic expression of CCR2 and MCP-1 was increased 10-fold and 20-fold, respectively, 12 to 72 hours after administration of acetaminophen to wild-type mice. Expression of these proteins was localized in centrilobular regions of the liver. Whereas MCP-1 was expressed by both hepatocytes and macrophages, CCR2 was identified in inflammatory macrophages. F4/80 is a marker of mature macrophages expressed in large quantities by Kupffer cells. In wild-type mice, a 75% decrease in F4/80-positive macrophages was observed 24 to 48 hours after administration of acetaminophen. In contrast, expression of macrosialin (CD68), a marker of activated macrophages, increased 2-fold 24 to 72 hours after administration of acetaminophen and was associated with inflammatory cells. Although there was a decrease in the overall severity of inflammation and in the number of macrosialin-positive macrophages 72 hours after administration of acetaminophen in CCR2-/- mice, the number of F4/80-positive cells did not change. Loss of CCR2 was also found to alter acetaminophen-induced expression of tumor necrosis factor alpha, monocyte chemoattractant protein 3, and KC/gro. However, the overall outcome of acetaminophen-induced hepatic injury was not affected. In conclusion, these data indicate that MCP-1 and CCR2 contribute to the recruitment of a subset of activated macrophages into the liver during acetaminophen-induced hepatotoxicity that may be important in resolution of tissue injury.

Acetaminophen↗
PubMed1997

Acetaminophen toxicity in an urban county hospital.

BACKGROUND: The prevalence and characteristics of acetaminophen-associated liver injury in hospitalized patients are not well defined. METHODS: We identified patients hospitalized for excessive acetaminophen ingestion at an urban county hospital over a 40-month period (1992 to 1995) and reviewed their medical records to determine the incidence and clinical features of the ingestions and their outcomes. RESULTS: Of the 71 patients studied, 50 were classified as having taken acetaminophen during suicide attempts and 21 as having accidentally poisoned themselves while attempting to relieve pain. The suicidal patients had ingested almost twice as much acetaminophen as those in the accidental-overdose group (median, 20 vs. 12 g; P=0.009). Among the patients for whom data were available, 63 percent of those in the accidental-overdose group and 25 percent of those in the suicidal group had chronic alcohol abuse (P=0.009). The patients in the accidental-overdose group more often had severe liver necrosis (aminotransferase levels, >3500 IU per liter; 52 percent vs. 14 percent; P=0.002), and were more likely to have hepatic coma (33 percent vs. 6 percent, P=0.006). There were four deaths (19 percent) in the accidental-overdose group and one (2 percent) in the suicidal group (P=0.04). Five patients -- three in the accidental-overdose group and two in the suicidal group -- had ingested 4 g of acetaminophen or less. Acetaminophen ingestion accounted for 12 percent of all patients hospitalized with overdoses (71 of 589) and 40 percent of patients with acute liver failure (10 of 25) during the study period. CONCLUSIONS: In an urban county hospital, patients hospitalized with acetaminophen toxicity related to accidental misuse had higher rates of morbidity and mortality than those who attempted suicide, even though the latter had taken more acetaminophen. A higher frequency of chronic alcohol abuse among the patients with accidental overdoses may be one explanation.

Accidents↗
PubMed2004

Acetaminophen-induced hypothermia in mice is mediated by a prostaglandin endoperoxide synthase 1 gene-derived protein.

Acetaminophen is a widely used antipyretic analgesic, reducing fever caused by bacterial and viral infections and by clinical trauma such as cancer or stroke. In rare cases in humans, e.g., in febrile children or HIV or stroke patients, acetaminophen causes hypothermia while therapeutic blood levels of the drug are maintained. In C57/BL6 mice, acetaminophen caused hypothermia that was dose related and maximum (>2 degrees C below normal) with a dose of 300 mg/kg. The reduction and recovery of body temperature was paralleled by a fall of >90% and a subsequent rise of prostaglandin (PG)E(2) concentrations in the brain. In cyclooxygenase (COX)-2(-/-) mice, acetaminophen (300 mg/kg) produced hypothermia accompanied by a reduction in brain PGE(2) levels, whereas in COX-1(-/-) mice, the hypothermia to this dose of acetaminophen was attenuated. The brains of COX-1(-/-) mice had approximately 70% lower levels of PGE(2) than those of WT animals, and these levels were not reduced further by acetaminophen. The putative selective COX-3 inhibitors antipyrine and aminopyrine also reduced basal body temperature and brain PGE(2) levels in normal mice. We propose that acetaminophen is a selective inhibitor of a COX-1 variant and this enzyme is involved in the continual synthesis of PGE(2) that maintains a normal body temperature. Thus, acetaminophen reduces basal body temperature below normal in mice most likely by inhibiting COX-3.

Acetaminophen↗
PubMed2002

Determinants of the cellular specificity of acetaminophen as an inhibitor of prostaglandin H(2) synthases.

Acetaminophen has antipyretic and analgesic properties yet differs from the nonsteroidal antiinflammatory drugs and inhibitors of prostaglandin H synthase (PGHS)-2 by exhibiting little effect on platelets or inflammation. We find parallel selectivity at a cellular level; acetaminophen inhibits PGHS activity with an IC(50) of 4.3 microM in interleukin (IL)-1 alpha-stimulated human umbilical vein endothelial cells, in contrast with an IC(50) of 1,870 microM for the platelet, with 2 microM arachidonic acid as substrate. This difference is not caused by isoform selectivity, because acetaminophen inhibits purified ovine PGHS-1 and murine recombinant PGHS-2 equally. We explored the hypothesis that this difference in cellular responsiveness results from antagonism of the reductant action of acetaminophen on the PGHSs by cellular peroxides. Increasing the peroxide product of the PGHS-cyclooxygenase, prostaglandin G(2) (PGG(2)), by elevating the concentration of either enzyme or substrate reverses the inhibitory action of acetaminophen, as does the addition of PGG(2) itself. 12-Hydroperoxyeicosatetraenoic acid (0.3 microM), a major product of the platelet, completely reverses the action of acetaminophen on PGHS-1. Inhibition of PGHS activity by acetaminophen in human umbilical vein endothelial cells is abrogated by t-butyl hydroperoxide. Together these findings support the hypothesis that the clinical action of acetaminophen is mediated by inhibition of PGHS activity, and that hydroperoxide concentration contributes to its cellular selectivity.

6-Ketoprostaglandin F1 alpha↗
PubMed1999

Acetaminophen toxicity. Opposite effects of two forms of glutathione peroxidase.

Acetaminophen is one of the most extensively used analgesics/antipyretics worldwide, and overdose or idiopathic reaction causes major morbidity and mortality in its victims. Research into the mechanisms of toxicity and possible therapeutic intervention is therefore essential. In this study, the response of transgenic mice overexpressing human antioxidant enzymes to acute acetaminophen overdose was investigated. Animals overexpressing superoxide dismutase or plasma glutathione peroxidase demonstrated dramatic resistance to acetaminophen toxicity. Intravenous injection of glutathione peroxidase provided normal mice with nearly complete protection against a lethal dose of acetaminophen. Surprisingly, animals overexpressing intracellular glutathione peroxidase in the liver were significantly more sensitive to acetaminophen toxicity compared with nontransgenic littermates. This sensitivity appears to be due to the inability of these animals to efficiently recover glutathione depleted as a result of acetaminophen metabolism. Finally, the results suggest that glutathione peroxidase overexpression modulates the synthesis of several acetaminophen metabolites. Our results demonstrate the ability of glutathione peroxidase levels to influence the outcome of acetaminophen toxicity.

Acetaminophen↗
PubMed1985

Failure of exogenous prostaglandin to afford complete protection against acetaminophen-induced hepatotoxicity in the rat.

The protective effect of 16, 16-dimethylprostaglandin E2 (dm-PGE2) against acetaminophen-induced hepatotoxicity was determined in the rat. The dm-PGE2 was administered at two dose levels both before and after acetaminophen administration. The hepatotoxicity was evaluated by a rise in serum transaminases 24 h after acetaminophen administration and by histological examination of liver preparations. The urinary acetaminophen and its metabolites were determined by high-pressure liquid chromatography. The results suggest that exogenous dm-PGE2 administration had a modest protection against acetaminophen-induced hepatotoxicity, in contrast to its well established cytoprotective effect against many noxious agents in the gastrointestinal tract. Prostaglandin treatment had little effect on acetaminophen metabolites excretion in the urine, suggesting that it did not affect the cytochrome P-450-dependent mixed-function oxidase drug-metabolizing enzyme system. The livers from dm-PGE2-acetaminophen-treated rats showed less advanced necrosis compared to those from saline-acetaminophen-treated rats. Whereas only 2 of 13 rats died in the prostaglandin-treated group, 4 of 13 rats died in the saline-treated group.

Acetaminophen↗
PubMed2005

Effects of acetaminophen on morphine side-effects and consumption after major surgery: meta-analysis of randomized controlled trials.

BACKGROUND: Acetaminophen is commonly used for the management of perioperative pain. However, there is a marked discrepancy between the extent to which acetaminophen is used and the available evidence for an analgesic effect after major surgery. The aim of this systematic review is to determine the morphine-sparing effect of acetaminophen combined with patient-controlled analgesia (PCA) with morphine and to evaluate its effects on opioid-related adverse effects. METHODS: MEDLINE and the Cochrane Library were searched to select randomized controlled trials which compared PCA morphine alone with PCA morphine plus acetaminophen administered orally or intravenously. Studies were evaluated for their quality based on the Oxford Quality Scale. Outcome measures were morphine consumption over the first 24 h after surgery, patient satisfaction and the incidence of morphine side-effects, including nausea and vomiting, sedation, urinary retention, pruritus and/or respiratory depression. RESULTS: Seven prospective randomized controlled trials, including 265 patients in the group with PCA morphine plus acetaminophen and 226 patients in the group with PCA morphine alone, were selected. Acetaminophen administration was not associated with a decrease in the incidence of morphine-related adverse effects or an increase in patient satisfaction. Adding acetaminophen to PCA was associated with a morphine-sparing effect of 20% (mean, -9 mg; CI -15 to -3 mg; P=0.003) over the first postoperative 24 h. CONCLUSION: Acetaminophen combined with PCA morphine induced a significant morphine-sparing effect but did not change the incidence of morphine-related adverse effects in the postoperative period.

Acetaminophen↗
PubMed1995

A double-blind evaluation of ketorolac tromethamine versus acetaminophen in pediatric tonsillectomy: analgesia and bleeding.

The study was designed to compare intravenous ketorolac to rectal acetaminophen for analgesia and bleeding in pediatric patients undergoing tonsillectomy. We studied 50 patients, aged 2-15 yr undergoing tonsillectomy with or without adenoidectomy. In a randomized, prospective double-blind fashion, patients were assigned to receive either ketorolac (1 mg/kg) or rectal acetaminophen (35 mg/kg). Bleeding was evaluated by measuring intraoperative blood loss and noting extra measures required to obtain hemostasis. Bleeding times were also measured before and during surgery. Pain was evaluated using a standard objective pain score for the first 3 h. Persistent pain was treated with morphine, acetaminophen, and codeine and recorded for 24 h. Blood for determination of acetaminophen levels was drawn at 20 and 40 min after the administration of study drugs. Pain scores were not significantly different between the ketorolac and acetaminophen groups. The majority of patients in both groups required additional opioid in the postoperative period. Acetaminophen levels were all less than the therapeutic range. Intraoperative bleeding times were normal in all patients, but blood loss was significantly higher in the ketorolac group (2.67 mL/kg) compared to the acetaminophen group (1.44 mL/kg), P = 0.025. Significantly more measures to achieve hemostasis were required in the ketorolac group (P = 0.012). We conclude that ketorolac is no more effective than high-dose rectal acetaminophen for analgesia in the patient undergoing tonsillectomy. Hemostasis during tonsillectomy was significantly more difficult to achieve in patients receiving ketorolac.

Acetaminophen↗
PubMed2000

The pharmacokinetics and analgesic efficacy of larger dose rectal acetaminophen (40 mg/kg) in adults: a double-blinded, randomized study.

UNLABELLED: Analgesic acetaminophen plasma concentrations are not known. We investigated in a randomized, double-blinded study the pharmacokinetics and analgesic efficacy of small- (AS; 20 mg. kg(-1)) and larger- (AL; 40 mg/kg) dose rectal acetaminophen and compared it with the combination (C) of rectal diclofenac (100 mg) and acetaminophen (20 mg/kg) in 65 women undergoing hysterectomy. Suppositories were administered after the induction of a standardized general anesthesia. Pain (measured by using a 10-cm visual analog scale) and morphine consumption (patient-controlled analgesia) were repeatedly assessed for 24 h. Acetaminophen plasma concentrations were measured by using a fluorescence polarization immunoassay. Antipyretic plasma concentrations (10-20 mg/L) after 40 mg/kg acetaminophen were not associated with improved analgesia or decreased opioid requirements; 20 mg/kg acetaminophen produced subtherapeutic plasma levels (<10 mg/L). Maximal plasma concentrations of 17.2 and 10.4 mg/L (P < 0.01, analysis of variance) were achieved after 4.2 and 3.6 h for the AL and AS groups, respectively. The only difference in clinical outcome was lower visual analog scale scores after acetaminophen/diclofenac (C 2.0 versus AS 3.2 and AL 3.4) 4 h after the induction (P < 0.05, analysis of variance). Acetaminophen pharmacokinetics in adults were similar to those observed in children. Analgesic plasma concentrations are likely to be higher than antipyretic plasma levels, which were only attained after twice the recommended rectal dose was administered. Analgesic plasma concentrations have yet to be determined but may be higher than those associated with antipyresis. IMPLICATIONS: Acetaminophen pharmacokinetics were comparable in adults and children. Plasma concentrations known to reduce fever did not produce better pain relief and were only achieved after twice the conventional dose was administered. Analgesic plasma concentrations have yet to be determined but may be higher than those associated with antipyresis.

Acetaminophen↗
PubMed1999

Morphine-sparing effect of acetaminophen in pediatric day-case surgery.

BACKGROUND: Postoperative pain is a major problem in day-case surgery in children. Nonsteroidal antiinflammatory drugs have gained popularity in management of pediatric surgical patients to reduce the need for opioids. The aim of this study was to evaluate the efficacy of different doses of rectal acetaminophen in day-case surgery in children. METHODS: A randomized, double-blinded, placebo-controlled study design was used. Patients (n = 120) were randomized to receive a single dose of 0, 20, 40, or 60 mg/kg of rectal acetaminophen after induction of anesthesia. General anesthesia was induced by mask ventilation with sevoflurane (7%) in nitrous oxide and oxygen and maintained with 2.5-4.0% end-tidal sevoflurane. Opioids or local anesthetics were not used. Postoperative pain was evaluated by behavioral assessment and physiologic measurements every 10 min after arrival at the postanesthesia care unit. The pain intensity was scored using a 0-100 visual analog scale used in the authors' clinic. The need for rescue medication, intravenous morphine 0.1 mg/kg, was decided by the nurse, who was unaware of the rectal acetaminophen dose. The parents were interviewed by phone after 24 h regarding pain and its treatment, nausea, and vomiting. Rescue analgesia at home was rectal ibuprofen, 10 mg/kg. RESULTS: In the postanesthesia care unit pain scores were significantly lower in the 40- and 60-mg/kg groups compared with placebo and 20-mg/kg groups. Acetaminophen resulted in a dose-related reduction in the number of children who required postoperative rescue opioid, with significance reached with 40 or 60 mg/kg doses. Calculated dose of acetaminophen at which 50% of the children not requiring a rescue opioid was 35 mg/kg. The need for rescue analgesia at home during the first 24 h after surgery was also significantly less in patients in the 40- or 60-mg/kg groups than in the 0- or 20-mg/kg groups (20-17 vs. 80-63%). Thirty-three percent of patients receiving placebo had postoperative nausea and vomiting, compared with 0-3% in groups receiving 40 or 60 mg/kg acetaminophen. CONCLUSIONS: A single dose of 40 or 60 mg/kg of rectal acetaminophen has a clear morphine-sparing effect in day-case surgery in children if administered at the induction of anesthesia. Moreover, children with adequate analgesia with acetaminophen have less postoperative nausea and vomiting.

Acetaminophen↗
PubMed1999

Pharmacokinetic interaction between acetaminophen and lansoprazole.

Because of its minimal gastric toxicity, acetaminophen is the analgesic of choice for patients with gastric acid-related disorders. Because proton pump inhibitors are widely used, concomitant prescription of acetaminophen and lansoprazole would be prevalent. This crossover study was conducted to investigate an acetaminophen-lansoprazole interaction. On one occasion, each of six healthy, fasted, male volunteers ingested 1.0 g acetaminophen dissolved in 200 mL water. On another occasion, at least 1 week apart, 30 mg lansoprazole was administered orally, simultaneously with acetaminophen, after pretreatment with the same dose of lansoprazole once daily for 2 days. Plasma acetaminophen concentrations were measured at 0, 0.25, 0.5, 0.75, 1, 2, 3, 5, and 8 hours after dosing. The peak plasma concentration of acetaminophen and the time to its occurrence were significantly higher and shorter, respectively, during the lansoprazole session than during the control session. Neither the elimination half-life nor the area under the curve was significantly different between the two sessions. Lansoprazole hastens the absorption of acetaminophen solution, but little modifies its elimination rate and bioavailability.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed2002

Continuous low-level heat wrap therapy provides more efficacy than Ibuprofen and acetaminophen for acute low back pain.

STUDY DESIGN: A prospective, randomized, single (investigator) blind, comparative efficacy trial was conducted. OBJECTIVE: To compare the efficacy of continuous low-level heat wrap therapy (40 C, 8 hours/day) with that of ibuprofen (1200 mg/day) and acetaminophen (4000 mg/day) in subjects with acute nonspecific low back pain. SUMMARY OF BACKGROUND DATA: The efficacy of topical heat methods, as compared with oral analgesic treatment of low back pain, has not been established. METHODS: Subjects (n = 371) were randomly assigned to heat wrap (n = 113), acetaminophen (n = 113), or ibuprofen (n = 106) for efficacy evaluation, or to oral placebo (n = 20) or unheated back wrap (n = 19) for blinding. Outcome measures included pain relief, muscle stiffness, lateral trunk flexibility, and disability. Efficacy was measured over two treatment days and two follow-up days. RESULTS: Day 1 pain relief for the heat wrap (mean, 2) was higher than for ibuprofen (mean, 1.51; P = 0.0007) or acetaminophen (mean, 1.32; P = 0.0001). Extended mean pain relief (Days 3 to 4) for the heat wrap (mean, 2.61) also was higher than for ibuprofen (mean, 1.68; P = 0.0001) or acetaminophen (mean, 1.95; P = 0.0009). Lateral trunk flexibility was improved with the heat wrap (mean change, 4.28 cm) during treatment (P </= 0.009 vs acetaminophen [mean change, 2.93 cm], P </= 0.001 vs ibuprofen [mean change, 2.51 cm]). The results were similar on Day 4. Day 1 reduction in muscle stiffness with the heat wrap (mean, 16.3) was greater than with acetaminophen (mean, 10.5; P = 0.001). Disability was reduced with the heat wrap (mean, 4.9), as compared with ibuprofen (mean, 2.7; P = 0.01) and acetaminophen (mean, 2.9; P = 0.0007), on Day 4. None of the adverse events were serious. The highest rate (10.4%) was reported in the ibuprofen group. CONCLUSION: Continuous low-level heat wrap therapy was superior to both acetaminophen and ibuprofen for treating low back pain.

Acetaminophen↗
PubMed1998

Acetaminophen is an inhibitor of hepatic N-acetyltransferase 2 in vitro and in vivo.

Slow acetylators of the polymorphic N-acetyltransferase 2 (NAT2, EC 2.3.1.5) suffer more often from side-effects of NAT-substrates than fast acetylators. Since concomitant administration of drugs may inhibit NAT2, we studied the influence of acetaminophen on NAT2 in human hepatic cytosol in vitro and in healthy individuals. In-vitro acetylation was assessed in liver homogenate of one fast and one slow acetylator using sulfamethazine as a test substrate. Acetaminophen competitively inhibited sulfamethazine acetylation in fast and slow acetylator liver samples with Ki values of acetaminophen of 2144 micromol/l and 712 micromol/l, respectively. In additional experiments, exposure of human liver cytosol to p-aminophenol, a putative precursor of acetaminophen in this reaction, revealed production of substantial amounts of acetaminophen, which indirectly suggests that acetaminophen may bind to the active site of NAT2. In-vivo acetylation was quantified with a urinary caffeine assay in 20 healthy volunteers at baseline and after repetitive oral administration of 1000 mg acetaminophen every 6 h for 1 day. The ratio of the acetylated caffeine metabolite acetyl-amino-6-formylamino-3-methyluracil to 1-methylxanthine was reduced by 30.9% (range 11.0-50.1%) in fast acetylators (n = 10) and by 19.3% (range 0.2-36.5%) in slow acetylators (n = 10). Acetaminophen, a widely used over-the-counter drug, which shares structural similarities with acetylated products, inhibits NAT2 both in vitro and in vivo. These findings suggest that even compounds which are not metabolized by NAT2 may inhibit the enzyme and reduce its metabolic capacity.

Acetaminophen↗
PubMedDate not supplied

The therapeutic use of acetaminophen in patients with liver disease.

Acetaminophen has been used safely and effectively for many years to manage pain and/or fever in patients of all ages. It is commonly recommended as first-line therapy for a variety of patients and conditions, including the elderly, children with viral illnesses, and patients with osteoarthritis, gastrointestinal conditions, bleeding disorders, cardiovascular disease, or renal disease. However, its use is often avoided in patients with chronic liver disease. The perception that acetaminophen should be avoided in such patients arose from awareness of the association between massive acetaminophen overdose and hepatotoxicity, combined with a lack of understanding of the metabolism of acetaminophen in patients with liver disease. There are various theoretical mechanisms of acetaminophen hepatotoxicity in chronic liver disease including: altered metabolism and depleted glutathione stores that would be expected to increase accumulation of the hepatotoxic intermediate, N-acetyl-p-benzoquinone imine (NAPQI). Available studies in patients with chronic liver disease, however, have shown that although the half-life of acetaminophen may be prolonged, cytochrome P-450 activity is not increased and glutathione stores are not depleted to critical levels in those taking recommended doses. Furthermore, acetaminophen has been studied in a variety of liver diseases without evidence of increased risk of hepatotoxicity at currently recommended doses. Therefore, acetaminophen can be used safely in patients with liver disease and is a preferred analgesic/antipyretic because of the absence of the platelet impairment, gastrointestinal toxicity, and nephrotoxicity associated with nonsteroidal antiinflammatory drugs.

Acetaminophen↗
PubMed2004

Acetaminophen dose accuracy and pediatric emergency care.

OBJECTIVE: To describe the demographic and clinical characteristics of children who receive acetaminophen per emergency department standing orders and identify factors associated with supratherapeutic doses (>or=16 mg/kg). METHODS: A cross-sectional retrospective study of consecutive children who received acetaminophen at an urban children's hospital emergency department. RESULTS: Over a 1-week period, 156 (24%) of 661 emergency department children were treated with acetaminophen. Of the children receiving acetaminophen, 64 (41%) were less than 2 years and 92 (59%) were males. The indication for acetaminophen was fever in 140 (90%) children, and 70 (50%) had temperatures >or=39degreesC. The route of administration was oral [133 (85%)] and rectal [23 (15%)]. There were 122 (78%) correct doses (standing order dose range of 10 to 15 mg/kg), 15 (10%) doses of <10 mg/kg, and 19 (12%, 95% CI, 8% to 18%) doses of >or=16 mg/kg. In comparison, children who received acetaminophen at normal or low doses (<16 mg/kg) versus supratherapeutic doses (>or=16 mg/kg) showed a significant difference in route. The rate of rectal route was significantly greater in the supratherapeutic doses (95% CI for changes in proportion, 14% to 48%). CONCLUSIONS: Review of acetaminophen dose accuracy, particularly the rectal route, is recommended for emergency departments with standing orders for acetaminophen.

Acetaminophen↗