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PubMed2001

Evaluation of occult acetaminophen hepatotoxicity in hospitalized children receiving acetaminophen. Pediatric Pharmacology Research Unit Network.

The safety of repeated doses of acetaminophen in ill children with the potential of reduced glutathione stores has been questioned. This study measured hepatic transaminases in children and adolescents (n=100) who received > or = 6 therapeutic doses of acetaminophen over a 48-hour period of hospitalization. Acetaminophen-protein adducts were measured in a cohort of subjects with hepatic transaminase elevation (n=8) and in those (n=10) receiving concurrent drug therapy with agents that induce the cytochrome P450 enzymes involved in acetaminophen metabolism. Acetaminophen-protein adducts were not detected in this cohort of 18 subjects. Based on this pilot study, the routine use of acetaminophen at therapeutic doses in ill, hospitalized children and adolescents appears safe.

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PubMed1990

Evaluation of ketorolac, ibuprofen, acetaminophen, and an acetaminophen-codeine combination in postoperative oral surgery pain.

Two-hundred six outpatients with postoperative pain after the surgical removal of impacted third molars were randomly assigned on a double-blind basis to receive oral doses of ketorolac tromethamine 10 and 20 mg, ibuprofen 400 mg, acetaminophen 600 mg, a combination of acetaminophen 600 mg plus codeine 60 mg, or placebo. Using a self-rating record, subjects rated their pain and its relief hourly for 6 hours after medicating. All active medications were significantly superior to placebo. Analgesia was similar for ketorolac 10 and 20 mg and ibuprofen 400 mg; however, these treatments were superior to acetaminophen alone and the acetaminophen-codeine combination. The analgesic effect of each active medication was significant by hour 1 and persisted for 5-6 hours. The data suggest a plateau in ketorolac's analgesic efficacy at the 10-mg level. Repeat-dose data indicated that on the day of surgery ketorolac 10 and 20 mg and ibuprofen 400 mg were superior to acetaminophen 600 mg; ketorolac 20 mg was also superior to acetaminophen-codeine. Differences among active medications were not significant when data for the entire postoperative period (days 0-6) were evaluated. The frequency of adverse effects was similar for the active medications.

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PubMed1978

Kinetics of metabolite formation and elimination in the perfused rat liver preparation: differences between the elimination of preformed acetaminophen and acetaminophen formed from phenacetin.

Both [14C]phenacetin and [3H]acetaminophen in tracer concentrations were perfused simultaneously once through the rat liver preparation at a constant perfusate flow rate (10 ml/min), and the rates of appearance of [14C]acetaminophen and [3H]acetaminophen in the effluent were compared. The data indicated that the extraction ratio of [14C]acetaminophen derived from [14C]phenacetin was smaller than that of the preformed [3H]acetaminophen added to the input perfusate (exogenously), i.e., the availability of the metabolite formed in situ was higher than the availability obtained when the metabolite was presented in the input blood. The observed availability of the acetaminophen derived from phenacetin was usually greater than that predicted by a "well-stirred" model and less than that predicted by a "parallel tube" model of hepatic drug clearance; the former model describes the liver as a well-stirred compartment with the drug in liver in equilibrium with that in the hepatic venous blood, and the latter model describes the liver as a group of identical and parallel uints with enzymes distributed evenly in hepatocytes lining the tubes. We conclude that the liver may be viewed as an imperfectly mixed compartment with regard to the availability of the metabolite which is generated from a precursor.

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PubMed2000

Hepatic disposition of the acyl glucuronide 1-O-gemfibrozil-beta-D-glucuronide: effects of clofibric acid, acetaminophen, and acetaminophen glucuronide.

Glucuronidation of carboxylic acid compounds results in the formation of electrophilic acyl glucuronides. Because of their polarity, carrier-mediated hepatic transport systems play an important role in determining both intra- and extrahepatic exposure to these reactive conjugates. We have previously shown that the hepatic membrane transport of 1-O-gemfibrozil-beta-D-glucuronide (GG) is carrier-mediated and inhibited by the organic anion dibromosulfophthalein. In this study, we examined the influence of 200 microM acetaminophen, acetaminophen glucuronide, and clofibric acid on the disposition of GG (3 microM) in the recirculating isolated perfused rat liver preparation. GG was taken up by the liver, excreted into bile, and hydrolyzed within the liver to gemfibrozil, which appeared in perfusate but not in bile. Mean +/- S. D. hepatic clearance, apparent intrinsic clearance, hepatic extraction ratio, and biliary excretion half-life of GG were 10.4 +/- 1.4 ml/min, 94.1 +/- 17.9 ml/min, 0.346 +/- 0.046, and 30.9 +/- 4.9 min, respectively, and approximately 73% of GG was excreted into bile. At the termination of the experiment (t = 90 min), the ratio of GG concentrations in perfusate, liver, and bile was 1:35:3136. Acetaminophen and acetaminophen glucuronide had no effect on the hepatic disposition of GG, suggesting relatively low affinities of acetaminophen conjugates for hepatic transport systems or the involvement of multiple transport systems for glucuronide conjugates. In contrast, clofibric acid increased the hepatic clearance, extraction ratio, and apparent intrinsic clearance of GG (P <.05) while decreasing its biliary excretion half-life (P <.05), suggesting an interaction between GG and hepatically generated clofibric acid glucuronide at the level of hepatic transport. However, the transporter protein(s) involved remains to be identified.

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PubMed1983

Suppression of postoperative pain by preoperative administration of ibuprofen in comparison to placebo, acetaminophen, and acetaminophen plus codeine.

The analgesic effect of preoperatively administered ibuprofen was evaluated in 107 dental outpatients undergoing the removal of impacted third molars. Subjects were given 800 mg ibuprofen prior to the procedure and 400 mg ibuprofen 4 and 8 hours later. Comparison was made to groups receiving either placebo at all three doses, 600 mg acetaminophen administered on the same schedule, or preoperatively administered placebo followed by two doses of postoperatively administered 600 mg acetaminophen plus 60 mg codeine. Ibuprofen pretreatment resulted in significantly less pain than placebo or acetaminophen pretreatment as the local anesthetic wore off. Ibuprofen also resulted in less postoperative pain than acetaminophen plus codeine following the second dose. Side effects were similar across drug treatments and placebo with the exception of greater reports of drowsiness following the opiate-analgesic combination. These findings indicate that pretreatment with a nonsteroidal antiinflammatory drug, such as ibuprofen, results in a suppression of postoperative pain when compared to standard therapy without an increase in side effects.

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PubMed2007

The effect of preoperative acetaminophen or a combination of acetaminophen and Ibuprofen on the success of inferior alveolar nerve block for teeth with irreversible pulpitis.

This study compared preoperative administration of acetaminophen or a combination of acetaminophen and ibuprofen versus placebo for potential increased effectiveness of inferior alveolar nerve (IAN) block anesthesia. There were 40 patients with irreversible pulpitis randomly assigned to a drug or placebo group. Thirty minutes after ingestion of medication, an IAN block was administered. A cold test was done 15 minutes after the block, and if the patients had no sensitivity, endodontic therapy was initiated. If the patient had no pain on access, the IAN was recorded as successful. If the patient had sensitivity to cold or to the access procedure, it was recorded as a failure. Overall success was 60% for all three groups. Success was 71.4% for the acetaminophen group, 75.9% for the acetaminophen and ibuprofen group, and 46.2% for the placebo group. There was no significant difference between the groups; however, there was a trend toward higher success in the medication groups.

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PubMed2005

Migration behaviour and separation of acetaminophen and p-aminophenol in capillary zone electrophoresis: analysis of drugs based on acetaminophen.

The migration behaviour of acetaminophen and p-aminophenol was investigated by capillary electrophoresis. The influence of different parameters (pH, nature and concentration of the running buffer and applied voltage) on the migration time, peak symmetry, efficiency and resolution was systematically investigated. The two analytes can be well separated within 4 min in a 57 cm fused-silica capillary at a separation voltage of 18 kV in a 50mM borate buffer adjusted to pH 9.5. Correlation coefficients for calibration curves in the range 0.2-200 microg ml-1 for acetaminophen and 0.3-3 microg ml-1 for p-aminophenol were higher than 0.999. The sensitivity of detection is 4.2 ng ml-1 for acetaminophen and 11.2 ng ml-1 for p-aminophenol. The method was applied to the analysis of various commercially available acetaminophen dosage forms with recoveries of 98.4-100.7%.

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PubMed2005

Contribution of acetaminophen-cysteine to acetaminophen nephrotoxicity II. Possible involvement of the gamma-glutamyl cycle.

Acetaminophen (APAP) nephrotoxicity has been observed both in humans and research animals. Our recent investigations have focused on the possible involvement of glutathione-derived APAP metabolites in APAP nephrotoxicity and have demonstrated that administration of acetaminophen-cysteine (APAP-CYS) potentiated APAP-induced renal injury with no effects on APAP-induced liver injury. Additionally, APAP-CYS treatment alone resulted in a dose-responsive renal GSH depletion. This APAP-CYS-induced renal GSH depletion could interfere with intrarenal detoxification of APAP or its toxic metabolite N-acetyl-p-benzoquinoneimine (NAPQI) and may be the mechanism responsible for the potentiation of APAP nephrotoxicity. Renal-specific GSH depletion has been demonstrated in mice and rats following administration of amino acid gamma-glutamyl acceptor substrates for gamma-glutamyl transpeptidase (gamma-GT). The present study sought to determine if APAP-CYS-induced renal glutathione depletion is the result of disruption of the gamma-glutamyl cycle through interaction with gamma-GT. The results confirmed that APAP-CYS-induced renal GSH depletion was antagonized by the gamma-glutamyl transpeptidase (gamma-GT) inhibitor acivicin. In vitro analysis demonstrated that APAP-CYS is a gamma-glutamyl acceptor for both murine and bovine renal gamma-GT. Analysis of urine from mice pretreated with acivicin and then treated with APAP, APAP-CYS, or acetaminophen-glutathione identified a gamma-glutamyl-cysteinyl-acetaminophen metabolite. These findings are consistent with the hypothesis that APAP-CYS contributes to APAP nephrotoxicity by depletion of renal GSH stores through interaction with the gamma-glutamyl cycle.

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PubMed1984

Determinants of acetaminophen metabolism: effect of inducers and inhibitors of drug metabolism on acetaminophen's metabolic pathways.

Acetaminophen metabolism and clearance after a single 1 gm oral dose of the drug was investigated in 12 healthy men, six of whom were cigarette smokers, and in six men who were receiving anticonvulsant drugs for epilepsy. The 12 healthy subjects were studied before and after 1 wk of pretreatment with cimetidine (1 gm/day) or sulfinpyrazone (800 mg/day). There was no significant difference in acetaminophen clearance (ClAP) between nonsmokers and smokers; cimetidine pretreatment had no effect on ClAP. Neither cigarette smoking nor cimetidine pretreatment had a significant effect on any of the metabolic pathways of acetaminophen. In contrast, sulfinpyrazone pretreatment increased ClAP by 23% (from 5.70 +/- 0.21 to 7.00 +/- 0.39 ml/min/kg) and ClAP was 46% greater in the epileptic subjects who received anticonvulsant drugs than in the control group (8.32 +/- 0.45 and 5.70 +/- 0.21 ml/ml/kg). In both cases the increase in ClAP was a result of induction of acetaminophen glucuronidation and oxidation; clearance of the glucuronic acid conjugate was 26% and 59% greater and clearance of the glutathione-derived conjugates (reflecting the activity of the oxidative pathway) was 43% and 60% greater in the groups given sulfinpyrazone and anticonvulsants, respectively.

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PubMed1993

Ketoprofen, acetaminophen plus oxycodone, and acetaminophen in the relief of postoperative pain.

Ketoprofen (Orudis) is a nonsteroidal anti-inflammatory drug that is currently approved in the United States for the management of mild to moderate pain. The objective of this trial was to determine the effectiveness of orally administered ketoprofen in the management of severe postoperative pain. This randomized, double-blind parallel study compared the efficacy and safety of single doses of 100 mg or 50 mg ketoprofen, the combination of 650 mg acetaminophen plus 10 mg oxycodone hydrochloride, 650 mg acetaminophen, or placebo in 240 patients with severe postoperative pain after cesarean section. Analgesia for the first dose was assessed over an 8-hour period. Multiple doses of 100 mg or 50 mg ketoprofen and the combination at half the dose (325 mg acetaminophen plus 5 mg oxycodone) were also assessed for up to 7 days. The 100 and 50 mg doses of ketoprofen and the combination were statistically superior to acetaminophen and placebo for many analgesic measures. A dose response was observed between the two doses of ketoprofen, with the 100 mg dose providing significantly greater analgesia over the lower dose. Ketoprofen, 100 mg, was at least as effective as the combination and its effects lasted longer, with the exception of hour 1 when the combination was superior. Remedication time for the group receiving 100 mg ketoprofen was significantly longer than for the other treatment groups. Significantly more patients who took repeated doses of the combination (84%) than those who took either dose of ketoprofen (70%) had adverse effects. Ketoprofen at both dose levels was shown to be effective, long-lasting, and well tolerated, and it should be considered as a viable option for the management of moderate to severe postoperative pain.

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PubMed1998

A dose-dependent delayed hypersensitivity reaction to acetaminophen after repeated acetaminophen intoxications.

We report a case of a 29-year-old woman with a borderline personality disorder who presented with intentional substantial acetaminophen (paracetamol) overdosage on nine occasions during a period of 21 months. In most cases, the patient presented at the hospital within 4 h after ingestion and was treated with gastric lavage, activated charcoal, laxatives and intravenous N-acetylcysteine. During the sixth overdosage the patient developed a rash on her chest and shoulders which was considered an anaphylactoid reaction to N-acetylcysteine. Therefore she was treated with oral methionine subsequently, but developed the rash again. The rash was then ascribed to the repeated high-doses of acetaminophen and treatment with N-acetylcysteine was reinstituted. This case shows that when an anaphylactoid reaction occurs after an acetaminophen overdose and treatment with N-acetylcysteine, acetaminophen must also be taken into account as the cause of the anaphylactoid reaction before effective therapy with N-acetylcysteine is withheld.

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PubMedDate not supplied

A 12-hour evaluation of the analgesic efficacy of diflunisal, acetaminophen, and acetaminophen-codeine combination, and placebo in postoperative pain.

The analgesic efficacy of single 500 and 1,000 mg doses of diflunisal, a new nonsteroidal antiinflammatory analgesic, was compared in a double-blind study with acetaminophen 600 mg, the combination of acetaminophen 600 mg with codeine 60 mg, and placebo in 132 inpatients with postoperative pain. Using a self-rating record, patients rated their pain and its relief hourly for up to 12 hours after medication. Diflunisal 500 and 1,000 mg were significantly superior to placebo for every measure of total and peak analgesia, and a significant analgesic effect persisted for 8 hours. Acetaminophen alone and the acetaminophen-codeine combination were significantly superior to placebo for most measures of analgesia, and their effects were significant for 4 and 5 hours respectively. Differences among the active medications were not statistically significant for measures of total or peak analgesia.

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PubMed1982

Metabolite kinetics: formation of acetaminophen from deuterated and nondeuterated phenacetin and acetanilide on acetaminophen sulfation kinetics in the perfused rat liver preparation.

The role of hepatic intrinsic clearance for metabolite formation from various precursors on subsequent metabolite elimination was was investigated in the once-through perfused rat liver preparation. Two pairs of acetaminophen precursors: [14C] phenacetin-d5 and [3H] phenacetin-do, [14C] acetanilide and [3H] phenacetin were delivered by constant flow (10 ml/min/liver) either by normal or retrograde perfusion to the rat liver preparations. The extents of acetaminophen sulfation were compared within the same preparation. The data showed that the higher the hepatocellular activity (intrinsic clearance) for acetaminophen formation, the greater the extent of subsequent acetaminophen sulfation. The findings were explained on the basis of blood transit time and metabolite "duration time." Because of blood having only a finite transit time in liver, the longer the drug requires for metabolite formation, the less time will remain for metabolite sulfation and the less will be the degree of subsequent sulfation. Conversely, when the drug forms the primary metabolite rapidly, a longer time will remain for the metabolite to be sulfated in liver to result in a greater degree of metabolite sulfation. Finally, the effects of hepatic intrinsic clearances for metabolite formation and zonal distribution of enzyme systems for metabolite formation and elimination in liver are discussed.

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PubMed1988

Dissociation of covalent binding from the oxidative effects of acetaminophen. Studies using dimethylated acetaminophen derivatives.

The cytotoxic effects of 10 mM acetaminophen (APAP) in primary cultures of non-induced mouse hepatocytes are accompanied by depletion of intracellular glutathione (GSH), arylation of protein, and loss of protein sulfhydryl (PSH) groups. Investigation of the stoichiometry of the covalent binding and PSH loss after APAP exposure demonstrated a greater loss in PSH than could be accounted for by covalent binding to proteins and suggests that APAP exhibits both oxidative and arylative actions in cell culture. Subcellular fractionation revealed that the PSH oxidation induced by APAP was greatest in the microsomal fraction. Exposure of the hepatocytes to 10 mM 3,5-dimethyl-acetaminophen (3,5-DMA) or 2,6-dimethyl-acetaminophen (2,6-DMA) permitted dissociation of the oxidative and arylative properties of APAP. Even though treatment of cultured hepatocytes with 3,5-DMA did not result in covalent binding, there was a more rapid depletion of intracellular GSH, oxidation of PSH, and cytotoxicity compared to APAP. This investigation also provides the first evidence that the cytotoxic effects of both APAP and 3,5-DMA are accompanied by the formation of protein aggregates of high molecular weight that are not disulfide linked. The aggregates probably reflect the oxidative properties of these drugs and may be a mediator of their toxic effects. By contrast, 2,6-DMA, which did bind to cellular proteins and deplete GSH, did not lead to PSH loss, protein aggregation, or cytotoxicity. Since PSH oxidation and protein aggregation correlated well with cytotoxicity, these data suggest that the oxidative component of APAP and 3,5-DMA can play a significant role in eliciting cellular damage in cultured hepatocytes.

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PubMed1987

A method for the preparation of calibration curves for acetaminophen glucuronide and acetaminophen sulfate in rabbit urine without use of authentic compounds in high-performance liquid chromatography.

A method for the preparation of calibration curves for acetaminophen glucuronide (NAPAG) and acetaminophen sulfate (NAPAS) in rabbit urine without use of authentic compounds in high-performance liquid chromatography was examined. Rabbits were dosed intravenously with acetaminophen (NAPA, 30 mg/kg). Urine was collected and diluted. A plot of the peak area ratio of NAPAG to internal standard against NAPA concentration after the hydrolysis of diluted urine with beta-glucuronidase was linear and passed through the origin. A linear tendency was also observed in the plot of the peak area ratio of NAPAS to internal standard against NAPA concentration calculated by the difference between the peak area ratio of NAPA after the hydrolysis with beta-glucuronidase and that with beta-glucuronidase/arylsulfatase. Thus, once the calibration curve has been prepared following the enzyme hydrolysis of NAPAG and NAPAS, then the concentration of NAPAG and NAPAS in the sample solution can be calculated from the peak of NAPAG and NAPAS, respectively. The method is simple, and has the advantage that pure standards of the individual NAPA metabolites are not required.

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PubMedDate not supplied

Analysis of the analgesic efficacy of acetaminophen 1000 mg, codeine phosphate 60 mg, and the combination of acetaminophen 1000 mg and codeine phosphate 60 mg in the relief of postoperative pain.

Patients who experienced pain after surgery were administered a single dose of 1 of 3 treatments: acetaminophen 1000 mg, codeine phosphate 60 mg, or a combination of these. Patients rated their pain intensity on ordinal and visual analog scales just prior to medication and at intervals thereafter for up to 5 hours. They also rated pain relief, pain half gone, and any adverse effects. Sum of pain intensity difference and total pain relief scores were analyzed using Dunnett's procedure. The drug combination was statistically superior to codeine as measured by SPID, TOTPAR, pain half gone, and time to remedication. The combination achieved better mean scores than acetaminophen on all efficacy measures, but was (marginally) statistically superior only in pain half gone. No appreciable differences in adverse effects were noted among the treatments. The difficulty of showing the analgesic efficacy of codeine in a single dose trial is discussed.

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PubMed1996

Evidence suggesting the 58-kDa acetaminophen binding protein is a preferential target for acetaminophen electrophile.

Acetaminophen is an analgesic and antipyretic which causes liver toxicity in humans and experimental animals with overdose. Acetaminophen (APAP) covalent binding to a cytosolic protein of approximately 58 kDa (58-ABP) has been associated with target organ toxicity. Since hepatic content of 58-ABP varies, studies were conducted to determine if this influences APAP binding to other target proteins. In the liver, the amount of 58-ABP varied with individual male CD-1 mice, but in kidneys of the same mice there was no such variability in 58-ABP content. All male A/J mice tested had comparatively little detectable 58-ABP in liver cytosol. Similarly, female CD-1 mice had low 58-ABP content compared to males; however, administration of testosterone propionate to females significantly increased 58-ABP content in liver cytosol. At 4 hr after challenge of mice from the above-described groups with 600 mg APAP/kg, cytosolic covalent binding to proteins was determined by Western blot analysis with anti-APAP antibody. The Western blots were then stripped of antibody and blocking agents and reprobed with antibody prepared against purified 58-ABP (anti-58-ABP). In the liver, the level of APAP bound to the 58-ABP target corresponded with 58-ABP content. In cases where 58-ABP was poorly expressed, APAP adducts to other protein targets were more prominently detected. In the kidneys of the male CD-1 mice 58-ABP arylation by APAP varied little among animals, reflecting the relatively consistent levels of renal 58-ABP. These data suggest that binding to the 58-ABP may spare other potential targets of APAP electrophile attach and support a role of the 58-ABP as a preferred target of APAP electrophile in cytosol.

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PubMed1986

Simultaneous determination of the major metabolites of styrene and acetaminophen, and of unchanged acetaminophen in urine by ion-pairing high-performance liquid chromatography.

An improved isocratic high-performance liquid chromatographic method for the quantitative determination of the major urinary metabolites of styrene in urine is described. The high separation efficiency of an ion-pairing system using tetrabutyl ammonium chloride allows also the simultaneous determination of acetaminophen and its three major metabolites with those of styrene in rat urine. Simplicity, reproducibility and a short analysis time provide a useful tool for the toxicokinetic studies of these two hepatorenotoxic xenobiotics after their co-administration. An aliquot of the diluted urine is directly injected into the liquid chromatograph. The limits of sensitivity and detection of the metabolites of styrene are better than those reported before. Preliminary works indicate that the method would also be applicable for analysis of these metabolites in human urine and would therefore be useful in monitoring styrene exposure to workers especially when they take acetaminophen.

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