Background L ocal infiltration analgesia ( LIA ) with local anaesthetic (ropivacaine), a nonsteroidal anti‐inflammatory drug (ketorolac) and epinephrine after lower extremity arthroplasty has gained increasing popularity during the last decade. This method has certain advantages, which include minimal systemic side effects, faster post‐operative mobilization, earlier post‐operative discharge from hospital and less opioid consumption. However, information regarding plasma concentrations of ketorolac after LIA mixture is insufficient to predict the risk of renal impairment in patients subjected to arthroplasty. Aim To determine the maximal plasma concentration and the exposure of ketorolac during the first 30 h following LIA in hip arthroplasty. Methods Thirteen patients scheduled for primary total hip arthroplasty with LIA (ropivacaine 200 mg, ketorolac 30 mg and epinephrine 0.5 mg in a volume of 106 ml) were included. Plasma concentration of ketorolac was quantified by liquid chromatography‐mass spectrometry. In addition, we assessed the effect of increasing age and decreasing glomerular filtration rate on the maximal plasma concentration and the total exposure to ketorolac during 30 h. Results The range of the maximal plasma concentration, 0.3–2.2 mg/l, was detected 30 min–4 h after completing the infiltration. Similar plasma levels have been reported after intramuscular injection of the same dose of ketorolac to healthy elderly volunteers. Conclusion Exposure to ketorolac after LIA may be comparable to an intramuscular injection of the same dose. Decision of dose reduction should be based on clinical assessment of risk factors.

Pain after total knee arthroplasty (TKA) is difficult to control. A recently developed and increasingly popular method for postoperative analgesia following knee and hip arthroplasty is Local Infiltration Analgesia (LIA) with ropivacaine, ketorolac and epinephrine. This method is considered to have certain advantages, which include administration at the site of traumatized tissue, minimal systemic side effects, faster postoperative mobilization, earlier postoperative discharge from hospital and less opioid consumption. One limitation, which may prevent the widespread use of LIA is the lack of information regarding plasma concentrations of ropivacaine and ketorolac. The aim of this academically initiated study was to detect any toxic or near-toxic plasma concentrations of ropivacaine and ketorolac following LIA after TKA. Methods Forty patients scheduled for primary total knee arthroplasty under spinal anaesthesia, were randomized to receive either local infiltration analgesia with a mixture of ropivacaine 300 mg, ketorolac 30mg and epinephrine or repeated femoral nerve block with ropivacaine in combination with three doses of 10mg intravenous ketorolac according to clinical routine. Plasma concentration of ropivacaine and ketorolac were quantified by liquid chromatography-mass spectrometry (LC-MS). Results The maximal detected ropivacaine plasma level in the LIA group was not statistically higher than in the femoral block group using the Mann-Whitney U-test (p = 0.08). However, the median concentration in the LIA group was significantly higher than in the femoral block group (p < 0.0001; Mann-Whitney U-test). The maximal plasma concentrations of ketorolac following administration of 30mg according to the LIA protocol were detected 1 h or 2 h after release of the tourniquet in the LIA group: 152-958 ng/ml (95% CI: 303-512 ng/ml; n = 20). The range of the plasma concentration of ketorolac 2-3 h after injection of a single dose of 10mg was 57-1216 ng/ml (95% CI: 162-420 ng/ml; n = 20). Conclusion During the first 24 h plasma concentration of ropivacaine seems to be lower after repeated femoral block than after LIA. Since the maximal ropivacaine level following LIA is detected around 4-6 h after release of the tourniquet, cardiac monitoring should cover this interval. Regarding ketorolac, our preliminary data indicate that the risk for concentration dependent side effects may be highest during the first hours after release of the tourniquet. Implication Femoral block may be the preferred method for postoperative analgesia in patients with increased risk for cardiac side effects from ropivacaine. Administration of a booster dose of ketorolac shortly after termination of the surgical procedure if LIA was used may result in an increased risk for toxicity.

BACKGROUND:Ketobemidone is often used as an alternative to morphine in children in the Scandinavian countries. In an earlier study, we have examined the pharmacokinetic properties in children in different age groups but have not focused on neonates. The aim of this clinical trial was to explore the pharmacokinetics of ketobemidone in neonates.METHODS:Fifteen full-term neonates (eight females) from 37 gestational weeks at birth and scheduled for elective surgery were included in the trial. Their median age was 3 days (range 1-18 days). Ketobemidone hydrochloride was administered as a single intravenous bolus dose, and ketobemidone concentrations were measured by liquid chromatography-mass spectrometry over 10 h. Pharmacokinetic parameters were calculated with standard compartmental methods.RESULTS:The median (range) values for ketobemidone clearance, apparent volume of distribution, volume of central compartment, distribution half-life and elimination half-life were 0.46 (0.23-0.84) l/h/kg, 4.64 (3.50-7.31) l/kg, 1.71 (0.16-3.47) l/kg, 2.85 (1.04-10.78) min and 7.26 (3.5-11.3) h.CONCLUSION:Compared with our previous study in children older than 1 year of age, the elimination of ketobemidone appeared to be slower in full-term neonates. Despite a low pharmacokinetic variability of ketobemidone as observed in the present neonatal patient population, we recommend individualizing the dose of ketobemidone based on observations of analgesic efficacy.

A method based on the direct injection of diluted urine for the identification and quantification of morphine, morphine-3-glucuronide, morphine-6-glucuronide, codeine, codeine-6-glucuronide, ethylmorphine, ethylmorphine-6-glucuronide and 6-acetylmorphine (6AM) in human urine by electrospray ionisation liquid chromatography-tandem mass spectrometry was validated for use as a confirmation procedure in urine drug testing. Four deuterium labelled analogues were used as internal standards: morphine-3-glucuronide-D3, morphine-D3, codeine-D3 and 6AM-D3. Twenty microlitre aliquots of urine were mixed with 80 mul of the internal standard solution in autosampler vials and 10 mul was injected. The chromatographic system consisted of a 2.0 x 100 mm C18 column and the gradient elution buffers used acetonitrile and 25 mmol/l formic acid. Two product ions produced from the protonated molecular ions were monitored in the selected reaction monitoring mode. The intra- and inter-assay variability (coefficient of variation) was below 10% at higher levels for all analytes, but at the reporting limits the variation was above 20% for 6AM, morphine-3-glucuronide and codeine-6-glucuronide. Ion suppression occurred early after injection but did not affect the identification and quantification of the analytes in authentic samples. The method was further validated by comparison with a reference gas chromatographic-mass spectrometric method using authentic urine samples. The two methods agreed almost completely (99%) regarding the identified analytes, but for the quantitative results there were slightly lower levels when measuring glucuronides directly as compared to total determination after hydrolysis by gas chromatography-mass spectrometry. We conclude that the presented liquid chromatographic-tandem mass spectrometric method is robust and reliable, and suitable for use as a confirmation method in urine drug testing for opiates

A method based on direct injection of diluted urine for the identification and quantification of amphetamine, methamphetamine, 3,4-methylenedioxymetamphetamine and 3,4-methylenedioxyamphetamine in human urine by electrospray ionisation liquid chromatography-tandem mass spectrometry was validated for use as a confirmation procedure in urine drug testing. Two deuterium labelled analogues, amphetamine-D5 and 3,4-methylenedioxymetamphetamine-D5, were used as internal standards. Twenty microliter aliquots of urine were mixed with 80 microL internal standard solution in autosampler vials and 10 microL was injected. The chromatographic system consisted of a 2.0 mmx100 mm C18 column and the gradient elution buffers used acetonitrile and 25 mmol/L formic acid. Two product ions produced from the protonated molecules were monitored in the selected reaction monitoring mode. The intra- and inter-assay variability (coefficient of variation) was between 5 and 16% for all analytes at 200 and 6000 ng/mL levels. Ion suppression occurred early after injection but did not affect the identification and quantification of the analytes in authentic urine samples. The method was further validated by comparison with a reference gas chromatographic-mass spectrometric method using 479 authentic urine samples. The two methods agreed almost completely (99.8%) regarding identified analytes when applying a 150 ng/mL reporting limit. Four deviating results were observed for 3,4-methylenedioxymethamphetamine and this was due to uncertainty in quantification around the reporting limit. For the quantitative results the slope of the regression lines were between 0.9769 and 1.0146, with correlation coefficients>0.9339. We conclude that the presented liquid chromatographic-tandem mass spectrometric method is robust and reliable, and suitable for use as a confirmation method in urine drug testing for amphetamines.

A method for the quantitative determination of perhexiline and its main hydroxylated metabolites in human plasma, based on liquid chromatography–mass spectrometry (LC–MS), was developed. The method used protein precipitation with acetonitrile followed by dilution with water and subsequent direct injection of the extract into the LC–MS system. Hexadiline was used as internal standard and the intra-assay coefficients of variation were ≤5% for perhexiline and cis-hydroxyperhexiline over the target concentration range in patients. The lower limits of quantification were 0.005mg/l for perhexiline and 0.015mg/l for cis-hydroxyperhexiline, and the measuring ranges were from 0.05 to 3.0 and from 0.2 to 6.0mg/l, respectively. The method was compared with an established HPLC method with fluorescence detection and the correlation between the methods was close to 1 for both compounds. The predominant form of hydroxyperhexiline in 87% of the patient samples was found to be one of the diastereomeric pairs of cis-hydroxyperhexiline. In patients not forming this metabolite, trans-hydroxyperhexiline could be detected. We conclude that the present LC–MS method is suitable for use in a clinical routine laboratory.

Background: Patients undergoing temporal bone surgery or subjects working with vibrating tools may develop vibration-induced hearing loss (VHL). The aim of this study was to characterize the effects of pretreatment with N-acetylcysteine (NAC) or the neurotrophic factors, brain-derived neurotrophic factor (BDNF) and ciliary neurotrophic factor (CNTF), on VHL in an animal model. Methods: Trauma to the cochlea was created with a vibrating probe placed on the bone of the external ear canal. BDNF and CNTFA×1 were delivered into the cochlea with mini-osmotic pumps. NAC was delivered into the cochlea by round window membrane (RWM) injection, by RWM permeation, or by oral administration. Hearing was evaluated with electrocochleography (ECoG). Results: For control animals, vibration resulted in an average immediate threshold shift of 42 ± 26 dB. NAC provided no protective benefit in animals subjected to VHL, regardless of the delivery method, with average threshold shifts varying from 38 to 56 dB across groups. NAC injection through the round window membrane was toxic, causing a ECoG threshold shift of >25 dB. In BDNF+CNTFA×1-treated animals, immediate hearing loss was similar to that in control animals. There was a trend of threshold recovery by 1 day after vibration; however, the improvement was not statistically significant, nor was there a significant difference in 1-day thresholds across groups. Conclusions: Local infusion of BDNF and CNTFA×1 may enhance the rate of recovery from VHL, compared to control animals. In contrast, NAC had no effect on VHL, and when delivered by RWM injection, was actually toxic to the inner ear.

This study compared the urinary excretion characteristics of ethyl glucuronide (EtG) with that of ethanol, with focus on the effect of water-induced diuresis. Six healthy volunteers ingested an ethanol dose of 0.5 g/kg (range 25.0-41.5 g) as 5% (v/v) beer in 30 min and the same volume of water after 3 h. Urine collections were made before starting the experiment and at timed intervals over 31.5 h. The concentration of EtG was determined by an LC-MS method (LOQ = 0.1 mg/L). The urine samples collected immediately before starting drinking were all negative for ethanol and EtG, thus confirming that the participants had not recently ingested alcohol. Intake of beer resulted in a marked increase in excreted urine volume and a concomitant drop in creatinine concentration. The concentration of ethanol peaked at a mean value of 17 mmol/L in the 1.5-h urine collection. Except for one subject, EtG was first detectable (range 0.9-5.5 mg/L) at 1 h. Intake of water at 3 h produced another increase in urine volume and a drop in creatinine. The ethanol concentration curve was not influenced by the water diuresis, whereas this caused a distinct drop in the EtG concentration. When EtG was expressed relative to the creatinine value, this ratio was seemingly not affected by the intake of water. The ethanol concentration returned to zero at 6.5 h, whereas EtG was still detectable for up to 22.5-31.5 h, albeit at low levels in the end (< 1 mg/l). Only about 0.02% of the administered dose of ethanol (on a molar basis) was recovered in the urine as EtG. The results demonstrated that EtG remains detectable in the urine for many hours after the ethanol itself has been eliminated. Moreover, it was possible to lower the concentration of EtG by drinking large amounts of water prior to voiding, whereas this strategy did not influence the EtG/creatinine ratio or the concentration of ethanol.

Ethyl glucuronide is a minor metabolite of ethanol, and its presence in urine can be used as a laboratory test to detect recent alcohol intake, even for some time after the ethanol is no longer measurable. A simple analytical procedure was developed based on direct injection of urine diluted with a deuterated internal standard into an electrospray liquid chromatographic-mass spectrometric (LC-MS) system. A novel LC system using a porous graphite column (Hypercarb) enabled an isocratic elution with retention times of 5-6 minutes. The intra- and inter-assay coefficients of variation were 2-12%, and the measuring range was 0.1-1,500 mg/L (0.45-6,750 mumol/L). Ethyl glucuronide was found to be stable in urine for more than 4 days at room temperature, and no artifactual formation was observed on storage of urine samples fortified with 1% ethanol. Ethyl glucuronide was not detected in urine samples collected after abstinence from alcohol. Intake of a very low amount (7 g) of ethanol produced ethyl glucuronide values up to 8.4 mg/L after 4 hours and was still detectable at 6 hours. When the method was applied for routine screening of 252 clinical urine samples (range, 0-1,240 mg/L), it fulfilled the need for a simple and reliable assay to be used in the evaluation of urinary ethyl glucuronide as a routine test of recent alcohol intake.