Effect of a spacer on total systemic and lung bioavailability in healthy volunteers and in vitro performance of the Symbicort® (budesonide/formoterol) pressurized metered dose inhaler.

INTRODUCTION: Many patients with chronic obstructive pulmonary disease or asthma experience difficulties in coordinating inhalation with pressurized metered-dose inhaler (pMDI) actuation. The use of a spacer device can improve drug delivery in these patients. The aim of this study was to establish the relative bioavailability of single doses of Symbicort® (budesonide/formoterol) pMDI 160/4.5 µg/actuation (2 actuations) used with and without a spacer device. In addition, an in vitro study was conducted to characterize performance of the inhaler when used in conjunction with a spacer device. METHODS: A Phase I, randomized, open-label, single-dose, single-center, crossover study in 50 healthy volunteers (NCT02934607) assessed the relative bioavailability of single-dose Symbicort® pMDI 160/4.5 µg/actuation (2 actuations) with and without a spacer (AeroChamber Plus® Flow-Vu®). Inhaled doses were administered without or with activated charcoal (taken orally) to estimate total systemic exposure and exposure through the lung, respectively. The in vitro study characterized the effect of the spacer with respect to delivered dose, fine particle dose, and dose during simulated breathing of budesonide and formoterol. RESULTS: In terms of total systemic exposure, use of the spacer increased the relative bioavailability determined by AUC(0-last) and Cmax by 68% (spacer:no spacer treatment ratio, 167.9%; 90% CI, 144.1 to 195.6) and 99% (ratio, 198.7%; 90% CI, 164.4 to 240.2) for budesonide, and 77% (ratio, 176.6%; 90% CI, 145.1 to 215.0) and 124% (ratio, 223.6%; 90% CI, 189.9 to 263.3) for formoterol, respectively, compared with pMDI alone. Similarly, the lung exposure of budesonide and formoterol increased (AUC(0-last) and Cmax by 146% [ratio, 246.0%; 90% CI, 200.7 to 301.6] and 127% [ratio, 226.5%; 90% CI, 186.4 to 275.4] for budesonide, and 173% [ratio, 272.8%; 90% CI, 202.5 to 367.4] and 136% [ratio, 236.2%; 90% CI, 192.6 to 289.6] for formoterol, respectively) when the pMDI was administered through the spacer. When assessed by AUC(0-last) quartile without spacer, subjects in the lowest exposure quartile (indicating poor inhalation technique) with Symbicort® pMDI 160/4.5 µg/actuation (2 actuations) had markedly increased total systemic and lung exposure when the same dose was administered with the spacer. In contrast, for subjects in the highest exposure quartile with pMDI alone, total systemic and lung exposure of formoterol and budesonide was similar with and without the spacer. In the in vitro study, the fine particle dose (<5 µm) of both budesonide and formoterol from the spacer at delay time (i.e. pause period after actuation) = 0 s (instantaneous) after actuation was similar to the fine particle dose when not using the spacer. The delivered doses of budesonide and formoterol from the spacer were both lower compared with the doses administered without the spacer. There was also a decrease in delivered dose with increasing delay time. CONCLUSIONS: The clinical study demonstrated that in subjects with poor inhalation technique the use of the AeroChamber Plus® Flow-Vu® spacer increased the bioavailability of Symbicort® pMDI to a level observed in subjects with good inhalation technique without a spacer. The findings from the in vitro study support the fine particle dose characteristics of Symbicort® pMDI with the AeroChamber Plus® Flow-Vu® spacer.

A novel mutation in the biliverdin reductase-A gene combined with liver cirrhosis results in hyperbiliverdinaemia (green jaundice).

BACKGROUND: Hyperbiliverdinaemia is a poorly defined clinical sign that has been infrequently reported in cases of liver cirrhosis or liver carcinoma, usually indicating a poor long-term prognosis. AIMS: To clarify the pathogenesis of hyperbiliverdinaemia in an extended case report. METHODS: A 64-year-old man with alcoholic cirrhosis was admitted to hospital with severe bleeding from oesophageal varices. Ultrasonography showed ascites, but no dilatation of the biliary tree. The skin, sclerae, plasma, urine and ascites of the patient showed a greenish appearance. Bilirubin levels were normal, and there were no signs of haemolysis. Biliverdin was analysed in plasma and urine with liquid chromatography coupled to mass spectrometry. The seven exonic regions of the biliverdin reductase-A (BVR-A) gene was amplified by polymerase chain reaction and sequenced. RESULTS: Biliverdin was present in plasma and urine. In nucleotide 52 of exon I of the DNA isolated from the hyperbiliverdinaemic patient, we discovered a novel heterozygous C-->T nonsense mutation converting an arginine (CGA) in position 18 into a stop codon (TGA) (R18Stop) predicted to truncate the protein N-terminally to the active site Tyr97. Two children of the proband were heterozygous for the identical mutation in the BVR-A gene, but had no clinical signs of liver disease and had normal levels of biliverdin. The BVR-A gene mutation was not found in 200 healthy volunteers or nine patients with end-stage liver cirrhosis. CONCLUSION: Hyperbiliverdinaemia (green jaundice) with green plasma and urine may be caused by a genetic defect in the BVR-A gene in conjunction with decompensated liver cirrhosis.

A novel polymorphism in ABCB1 gene, CYP2B6*6 and sex predict single-dose efavirenz population pharmacokinetics in Ugandans.

AIMS: Efavirenz exhibits pharmacokinetic variability causing varied clinical response. The aim was to develop an integrated population pharmacokinetic/pharmacogenetic model and investigate the impact of genetic variations, sex, demographic and biochemical variables on single-dose efavirenz pharmacokinetics among Ugandan subjects, using NONMEM. METHODS: Efavirenz plasma concentrations (n = 402) from 121 healthy subjects were quantified by high-performance liquid chromatography. Subjects were genotyped for 30 single nucleotide polymorphisms (SNPs), of which six were novel SNPs in CYP2B6, CYP3A5 and ABCB1. The efavirenz pharmacokinetics was described by a two-compartment model with zero- followed by first-order absorption. RESULTS: Apparent oral clearance (95% confidence interval) was 4 l h l(-1) (3.5, 4.5) in extensive metabolizers. In the final model, incorporating multiple covariates, statistical significance was found only for CYP2B6*6 and CYP2B6*11 on apparent oral clearance as well as ABCB1 (rs3842) on the relative bioavailability. Subjects homozygous for CYP2B6*6 (G516T, A785G) and *11 displayed 21 and 20% lower apparent oral clearance, respectively. Efavirenz relative bioavailability was 26% higher in subjects homozygous for ABCB1 (rs3842). The apparent peripheral volume of distribution was twofold higher in women compared with men. CONCLUSIONS: The model identified the four factors CYP2B6*6, CYP2B6*11, a novel variant allele in ABCB1 (rs3842) and sex as major predictors of efavirenz plasma exposure in a healthy Ugandan population after single-dose administration. Use of mixed-effects modelling allowed the analysis and integration of multiple pharmacogenetic and demographic covariates in a pharmacokinetic population model.

Determination of nebulizer droplet size distribution: a method based on impactor refrigeration.

Size distributions of droplets generated by nebulizers are difficult to determine because of evaporation after aerosolization. We describe a method whereby a Next Generation Pharmaceutical Impactor (NGI; MSP Corporation, Shoreview, MN) is refrigerated at 5 degrees C before connecting it to the nebulizer in order to ensure an environment inside the NGI at close to 100% relative humidity (RH). This, in turn, reduces droplet evaporation between the nebulizer and impaction. The method development was performed with a Pari LC Plus jet nebulizer operated at 2.0 bar, with the NGI set at a flow rate of 15 L/min and with salbutamol 5.0 mg/mL as the test solution. The droplet size distributions were expressed in terms of mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD). Variation in test conditions showed that the NGI should be cooled for at least 90 min, that nebulization should be started within 5 min after removal from the refrigerator, and that coating of collecting cups to prevent "bouncing" is not necessary. Variation of ambient temperature and humidity had no relevant effect on results. MMAD and GSD results showed that refrigeration of the NGI resulted in droplet size distributions that are likely to reflect those originally delivered at the mouthpiece by the nebulizer. The method was shown to be robust, accurate with recovery of test solutions exceeding 99%, reproducible, and to be suitable for use with a wide range of commercially available nebulizers.

Cerebrospinal fluid HIV-1 RNA, intrathecal immunoactivation, and drug concentrations after treatment with a combination of saquinavir, nelfinavir, and two nucleoside analogues: the M61022 study.

BACKGROUND: The way various antiretroviral drugs and drug combinations affect HIV-1 infection in the central nervous system is still largely unknown. The aim of this study was to determine the cerebrospinal fluid (CSF) steady-state concentrations of saquinavir and nelfinavir in relation to plasma concentrations, and to study their effect in combination with two nucleoside reverse transcriptase inhibitors (NRTIs) on CSF viral loads, intrathecal immunoactivation, and blood-brain barrier integrity. METHODS: Paired CSF and plasma samples from 8 antiretroviral-naïve HIV-1 infected patients starting combination therapy with saquinavir, nelfinavir, and two nucleoside analogues were collected prior to treatment, and again after approximately 12 and 48 weeks of antiretroviral therapy. Additional plasma samples were taken at weeks 2, 4, 8, 24, and 36. The concentrations of protease inhibitors were analysed, as were levels of HIV-1 RNA, CD4+ T-cell count, beta2-microglobulin, neopterin, albumin ratio, IgG index, and monocytic cell count. RESULTS: None of the patients in the study presented with HIV-1 RNA < 50 copies/mL in CSF or plasma prior to treatment, compared to 5/7 at the end of the study. Signs of cell-mediated intrathecal immunoactivation, measured by neopterin and beta2-microglobulin, decreased significantly in both CSF and serum, although only 1/7 reached normal CSF neopterin levels after 48 weeks of treatment. There was no significant reduction of albumin ratio, IgG index or CSF monocytic cell count. Saquinavir median (range) concentrations were < 2.5 (< 2.5-96.0) nM unbound in plasma, and < 2.5 (< 2.5-9.0) nM total in CSF. Nelfinavir median (range) concentrations were 10.0 (< 2.0-31.0) nM unbound in plasma, and < 2.0 (< 2.0-23.0) nM total in CSF. Saquinavir and nelfinavir were detectable in 7/15 and 9/15 CSF samples, respectively. CONCLUSION: Saquinavir and nelfinavir, in combination with two NRTIs, decrease the CSF viral load and, to a lesser extent, intrathecal immunoactivation. We found reasonably high CSF concentrations of nelfinavir, but suboptimal concentrations of saquinavir.

Simultaneous quantification of alprazolam, 4- and alpha-hydroxyalprazolam in plasma samples using liquid chromatography mass spectrometry.

A sensitive and specific method was developed for quantification of alprazolam and its two metabolites 4-hydroxyalprazolam and alpha-hydroxyalprazolam in plasma. The work up procedure was solid phase extraction. Liquid chromatography-mass spectrometry (LC-MS) was used for separation, detection and quantification of the analytes. The limit of quantitation (LOQ) was 0.05 ng/mL for alprazolam and the two metabolites. The extraction recovery was more than 82% for alprazolam and its metabolites. The within- and between-assay coefficients of variation were in the range of 1.9-17.9%. The method was used for determination of the pharmacokinetics parameters of alprazolam and its two metabolites in healthy Caucasian subjects who ingested 1mg of alprazolam.

Maintenance therapy with zuclopenthixol decanoate: associations between plasma concentrations, neurological side effects and CYP2D6 genotype.

RATIONALE: Several antipsychotic drugs are metabolised by the polymorphic cytochrome P(450) CYP2D6. The impact of the polymorphism on the plasma levels and the occurrence of side effects have not been clearly established. OBJECTIVE: To investigate the impact of the CYP2D6 polymorphism on the steady-state plasma concentrations of zuclopenthixol and the occurrence of extrapyramidal side effects (EPS) and tardive dyskinesia (TD) during treatment with zuclopenthixol-decanoate. METHODS: Fifty-two clinically stable schizophrenic outpatients on monotherapy with zuclopenthixol-decanoate (100-400 mg/4 weeks) were genotyped for the CYP2D6 variants CYP2D6*3 and CYP2D6*4. Steady-state plasma levels of zuclopenthixol were analysed using high-performance liquid chromatography. Assessments of EPS, TD and psychopathology were performed twice with an 8-week interval using the extrapyramidal symptoms rating scale, the abnormal involuntary movement scale and the brief psychiatric rating scale. RESULTS: Thirty-five patients were homozygous extensive metabolisers (EMs), 13 were heterozygous EMs and 4 were poor metabolisers (PMs). While there were no significant genotype-related differences in the doses of zuclopenthixol decanoate, PMs as well as heterozygous EMs had significantly higher steady-state plasma levels of zuclopenthixol than homozygous EMs (median 9.5 nmol/l; 8.2 nmol/l and 5.9 nmol/l, respectively, P<0.05). The median dose-corrected plasma concentrations were 0.029, 0.038 and 0.048 nmol.l(-1).mg(-1) in homozygous EMs, heterozygous EMs and PMs, respectively, with statistically significant differences between homozygous EMs and heterozygous EMs ( P=0.014) and homozygous EMs and PMs ( P=0.03). Patients with neurological side effects were significantly older than patients without ( P=0.02 in case of parkinsonism and P=0.04 in case of TD). Mutant CYP2D6*3 and *4 alleles tended to occur more frequently in patients with neurological side effects. An odds ratio (OR) of 2.3 (95% confidence interval 0.7-6.9) for development of parkinsonism and an OR of 1.7 (95% confidence interval 0.5-4.9) for TD was calculated in an individual with at least one mutated allele. However, the ORs were not statistically significant. CONCLUSIONS: The higher zuclopenthixol steady-state plasma concentrations in heterozygous EM and PM schizophrenic patients receiving monotherapy with zuclopenthixol-decanoate than in homozygous EMs indicates a significant role of CYP2D6 in the systemic elimination of zuclopenthixol. The tendencies for patients carrying at least one mutated CYP2D6 gene to have an increased risk of parkinsonism and TD are in accordance with previous studies. Age was a significant risk factor for neurological side effects.

Comparison of the antinociceptive effect of morphine, methadone, buprenorphine and codeine in two substrains of Sprague-Dawley rats.

Sprague-Dawley rats from two different vendors, Möllegård, Denmark and B&K Universal, Sweden, have been tested for the antinociceptive effect of morphine, methadone, buprenorphine and codeine on the hot plate. Morphine and methadone had significantly weaker effect in Möllegård rats compare to B&K rats. In contrast, the effect of buprenorphine was stronger in Möllegård rats than in B&K rats and the effect of codeine was similar in the two substrains. Plasma levels of morphine, morphine-6-glucuronide, morphine-3-glucuronide, buprenorphine and norbuprenorphine were determined at two time points after drug injection. Möllegård rats had significantly lower mean plasma level of morphine and significantly higher ratio of morphine-3-glucuronide/morphine at 30 min, compared to B&K rats. No difference was seen for the metabolism of buprenorphine in the two substrains. The results suggest that Möllegård rats metabolize morphine to morphine-3-glucuronide to a greater extent than B&K rats, and this may at least partly underlie the substrain difference in the effect of morphine. It is also suggested that the antinociceptive mechanisms of buprenorphne may be different from those of morphine and methadone.

A simple pharmacokinetic method to evaluate the pulmonary dose in clinical practice--analyses of inhaled sodium cromoglycate.

When the expected effect of an inhaled drug is not achieved, the cause could be poor inhalation technique and consequently a low pulmonary dose. A simple in vivo test to evaluate the pulmonary dose would be a benefit. This study evaluates the relative and systemic bioavailability following inhalation of nebulized sodium cromoglycate (SCG) in healthy subjects. Blood samples were collected during 240 min and urine was collected in two portions, up to 6 h post-inhalation. Two exposures were performed and comparisons based on the quantification of drug in plasma and urine by a high-performance liquid chromatography (HPLC) procedure were done. In one of the exposures, a pulmonary function test was performed to study if an expected effect of increased absorption could be detected. There was a good correlation between the two exposures shown in the plasma concentrations, but not in the urine analyses. The forced exhaled volume manoeuvres were associated with a higher Cmax and plasma concentrations up to 60 min post-inhalation (P<0.01). This effect was not detected in the urine analyses. We conclude that this pharmacokinetic method with inhaled SCG and plasma analyses could be used to evaluate individual inhalation technique. The HPLC method used was rapid and had adequate sensitivity.

Determination of phenprocoumon, warfarin and their monohydroxylated metabolites in human plasma and urine by liquid chromatography-mass spectrometry after solid-phase extraction.

A high-performance liquid chromatography-mass spectrometry (HPLC-MS) method for the quantification of phenprocoumon, warfarin, and their known monohydroxylated metabolites in human plasma and urine was developed using a simple, selective solid-phase extraction scheme. Chromatographic separation was achieved on a reversed-phase Luna C18 column and step gradient elution resulted in a total run time of about 13 min. Limits of quantification (LOQ) were < or = 40 nM for the parent compounds and < or = 25 nM for the metabolites and the limit of detection (LOD) was < or = 2.5 nM for all analytes. Average recovery was 84% (+/- 3.7) and 74% (+/- 13.2) in plasma and urine, respectively. Intra- and inter-day coefficients of variation were < or = 8.6 and < or = 10.6% in plasma and urine, respectively. The method was successfully applied to the analysis of phenprocoumon samples from four healthy volunteers and should prove useful for future comparative studies of warfarin and phenprocoumon pharmacokinetics.

[A case report. Unconscious patient with neon yellow skin was intoxicated with dipyridamole]. / Fallbeskrivning. Medvetslös patient med neongul hud var intoxikerad med dipyridamol.

A 66-year old man called for an ambulance from his home because of acute chest pain. When the crew arrived he was unresponsive and hypotensive. Sublingual nitroglycerine was given and subsequently the patient collapsed into circulatory failure and respiratory arrest. He was intubated and transported to the nearest hospital. The severe hypotension was combated with fluids and norepinephrine. During the next few hours his skin gradually turned intensely yellow, as did the urine. Acute myocardial infarction also occurred and renal failure developed. The cause of the neon-yellow colour was a complete mystery until a police patrol sent to his apartment found several empty packages of dipyridamole (Persantin Depot) corresponding to 34 g, an overdose seven times higher than any previous case reported in the literature. This drug has a distinct yellowish colour. The patient's condition gradually improved and he could be extubated within a week. Haemodialysis was needed for two weeks because of acute tubular necrosis after the prolonged period of hypotension, but thereafter he recovered.

[Guidelines for management of patients with pancreatic cancer]. / Riktlinjer för handläggning av patienter med pankreascancer.

The incidence of pancreatic cancer has fallen during the last ten years in Sweden. Early signs and symptoms of the disease are still undiscovered and when diagnosis is made the disease is incurable in most patients. Transabdominal ultrasonography is the first-line imaging test followed by spiral computed tomography (CT) and magnetic resonance imaging (MRI) if required for definite diagnosis. Spiral CT is also the imaging test of choice for assessment of resectability of the tumor. Surgical removal of the tumor is the only chance of cure. Markedly improved hospital mortality after pancreaticoduodenectomy is reported and an association between hospital volume and outcome of the operation has been established. Longterm survival after attempted curative resection continues to be dismal, however. Adjuvant treatment should not be given outside clinical studies. Palliative treatment has improved thanks to progress in the field of endoscopy, interventional radiology and in management of pain and nutrition. Palliative chemotherapy should only be given selectively outside clinical studies. Radiotherapy has no proven effects on survival. Special pancreatic cancer treatment teams with catchment areas of 2-4 million inhabitants are recommended by international authorities.

CYP2D6 genotype in relation to perphenazine concentration and pituitary pharmacodynamic tissue sensitivity in Asians: CYP2D6-serotonin-dopamine crosstalk revisited.

OBJECTIVES: Hyperprolactinemia is a common side effect of first-generation antipsychotics mediated by antagonism of dopaminergic neurotransmission in the pituitary. Most first-generation antipsychotics are metabolized by CYP2D6 in the liver. Further, CYP2D6 is expressed in the human brain as a 5-methoxyindolethylamine O-demethylase potentially contributing to regeneration of serotonin from 5-methoxytryptamine. As dopaminergic neurotransmission is subject to regulation by serotonin, CYP2D6 may exert a nuanced (serotonergic) influence on dopaminergic tone in the pituitary. CYP2D6*10 is an allele associated with reduced enzyme function and occurs in high frequency (about 50%) in Asians. We prospectively evaluated significance of CYP2D6 genetic variation for prolactin response to perphenazine (a model first-generation antipsychotic) in Asians. METHODS: A single oral dose of perphenazine (0.1 mg/kg) or placebo was administered to 22 medication-free nonsmoker healthy male Chinese-Canadian volunteers, following a double-blind within-subject randomized design. Blood samples were drawn at baseline and 2, 3, 4, 5 and 6 h after drug administration. RESULTS: In volunteers with CYP2D6*10/CYP2D6*10 genotype, the mean area under curve (AUC0-6) for perphenazine concentration was 2.9-fold higher than those who carry the CYP2D6*1 allele (P<0.01). Notably, volunteers homozygous for CYP2D6*10 exhibited a significant reduction (66%) in mean pharmacodynamic tissue sensitivity as measured by the (prolactin-AUC0-6/perphenazine-AUC0-6) ratio (P=0.02). CONCLUSIONS: CYP2D6 genotype is a significant contributor to perphenazine concentration in Chinese-Canadians. Importantly, prolactin response, when normalized per unit perphenazine concentration, appears to be blunted in volunteers homozygous for CYP2D6*10. We suggest that CYP2D6 genetic variation may potentially influence pharmacodynamic tissue sensitivity in the pituitary, presumably through disposition of an endogenous substrate (e.g. 5-methoxytryptamine).

The aciclovir metabolite CMMG is detectable in the CSF of subjects with neuropsychiatric symptoms during aciclovir and valaciclovir treatment.

OBJECTIVES: Neuropsychiatric symptoms related to aciclovir or valaciclovir treatment have been a problem since aciclovir was introduced in the early 1980s. We have previously found that subjects with aciclovir-related neuropsychiatric symptoms have increased serum concentrations of aciclovir's main metabolite, 9-carboxymethoxymethylguanine (CMMG). The aim of this study was to investigate whether CMMG was present in the CSF of aciclovir- or valaciclovir-treated subjects with or without neuropsychiatric side effects that appeared during therapy. METHODS: We investigated retrospectively CSF collected from 21 aciclovir- or valaciclovir-treated subjects. Of these, 9 were subjects with neuropsychiatric signs and symptoms and 12 were asymptomatic subjects, including 10 subjects from a valaciclovir multiple sclerosis trial and 2 subjects with recurrent herpes encephalitis. RESULTS: CMMG could only be detected in the CSF of subjects with neuropsychiatric symptoms and signs (median CMMG concentration 1.0 micromol/L, range 0.6-7.0). The concentration of CMMG was below the limit of quantification (<0.5 micromol/L) in asymptomatic subjects (P < 0.001). All patients with neuropsychiatric signs and symptoms, except one, had acute renal function impairment or chronic renal failure. CONCLUSIONS: These results are consistent with the hypothesis that CMMG is involved in the development of neuropsychiatric side effects in aciclovir- or valaciclovir-treated patients. Measurement of CMMG in CSF and/or serum is a promising tool in the diagnostic procedure for aciclovir- or valaciclovir-treated patients with neuropsychiatric symptoms and may help to differentiate between side effects and herpes encephalitis.

Alprazolam as a probe for CYP3A using a single blood sample: pharmacokinetics of parent drug, and of alpha- and 4-hydroxy metabolites in healthy subjects.

OBJECTIVES: (1) To determine the pharmacokinetic parameters of alprazolam and its two metabolites in plasma from healthy volunteers; (2) to identify a suitable single time point to take a plasma sample for CYP3A phenotyping. METHODS: Twelve healthy Swedish volunteers received a single oral dose of 1 mg alprazolam. Blood samples were collected before drug intake and frequently up to 72 h thereafter. A liquid-chromatography/mass-spectrometry (LC/MS) method was used for the quantification of alprazolam, and 4- and alpha-hydroxyalprazolam. RESULTS: The interindividual variation in the area under the concentration-time curve (AUC) was two, three and fourfold for alprazolam, 4-hydroxyalprazolam and alpha-hydroxyalprazolam, respectively. Plasma concentration ratios collected between 1 h and 48 h for both alprazolam/4-hydroxyalprazolam and alprazolam/alpha-hydroxyalprazolam correlated significantly to the corresponding AUC0-infinity ratios. CONCLUSIONS: The metabolic ratios of alprazolam to respective metabolite in a single plasma sample at 3-24 h are suggested to reflect the alprazolam 4- and alpha-hydroxylation activities. In future, it will be important to study these activities in populations where CYP3A5, in addition to CYP3A4, is expressed at a high frequency and to clarify the relative importance of the two enzymatic pathways for in vivo clearance of alprazolam.

Efavirenz plasma concentrations in HIV-infected patients: inter- and intraindividual variability and clinical effects.

Efavirenz is a drug subject to extensive metabolism, mainly by the cytochrome P-450 isoenzyme CYP2B6, known to exhibit extensive interindividual variability. The aim of the present study was 2-fold: to investigate the relationship between plasma concentration and clinical effects of efavirenz and to investigate the extent of the inter- and intraindividual variability of the plasma concentration measurements. From an open clinic, 68 HIV-positive patients on efavirenz-containing treatment were recruited. From each patient 1 to 5 samples were collected; 43 had more than 1 sample taken. Most samples were taken 10-24 hours after the latest dose. Efavirenz was analyzed by high-performance liquid chromatography with UV detection. The data were analyzed by the variance component model analysis of variance. Efavirenz concentrations were reproducible, and intraindividual variability constituted only 16% of the total variance. Thus, 84% of the variance was attributed to interindividual variability. The incidence of primary treatment failure was related to low plasma concentrations with a geometric mean concentration of 6.1 micromol/L compared with 8.7 micromol/L in those responding to therapy (P < 0.05). If a cutoff of 7 micromol/L is used, 10 of 13 failing to respond were below this level compared with 15 of 45 in those responding. It is concluded that efavirenz plasma concentration measurement gives reproducible results predictive of primary treatment failure. A lower bound for the therapeutic level of 7 micromol/L is proposed, and data from other authors suggests that an upper level of 13 micromol/L may be applied.

Interpretation of the presence of 6-monoacetylmorphine in the absence of morphine-3-glucuronide in urine samples: evidence of heroin abuse.

The presence of morphine in a urinary sample may be caused not only by intake of heroin but also by intake of poppy-seed-containing food shortly before urine sampling or intake of drugs containing morphine, ethyl morphine, or codeine. To facilitate the interpretation, the heroin-specific metabolite 6-monoacetylmorphine (6-MAM) can be analyzed along with morphine-3-glucuronide (M3G) in an LC-MS verification analysis. In sporadic samples positive in the immunologic opiate screening test, 6-MAM, but not M3G, was found. To systematically analyze the finding all specimens with positive 6-MAM and/or M3G found during a 1-year period were investigated (n = 1923). Of these, 423 were positive for 6-MAM. In 32 (7.6%) of the samples 6-MAM was detected while the M3G concentrations were below cutoff (300 ng/mL) and in some cases even below the limit of detection (15 ng/mL). The 32 samples with this excretion pattern came from 13 different individuals, all but one with previously known heroin abuse. Eleven urine samples, nine containing M3G and 6-MAM and two with only 6-MAM, were also analyzed for the presence of heroin. In six samples, including the two with only 6-MAM, heroin was detected. There are several plausible explanations for these findings. The intake may have taken place shortly before urine sampling. High concentrations of heroin and 6-MAM may inhibit UGT 2B7, the enzyme responsible for glucuronidation of morphine. The hydrolyzation of 6-MAM to morphine may be disturbed by either internal or external causes. To elucidate this, further studies are required. Nevertheless, our finding demonstrates that routine measurement of 6-MAM when verifying opioid-positive immunologic screening results facilitates interpretation of low concentrations of M3G in urine specimens.

High serum concentrations of the acyclovir main metabolite 9-carboxymethoxymethylguanine in renal failure patients with acyclovir-related neuropsychiatric side effects: an observational study.

BACKGROUND: Acyclovir (ACV) has been used for over two decades to treat herpes virus infections. Serious neurological adverse side effects have occurred during ACV treatment in patients with renal failure, but the cause of the symptoms remains unknown. We hypothesized that increased concentrations of the ACV main metabolite 9-carboxymethoxymethylguanine (CMMG) correlated to these symptoms. METHODS: We conducted an observational study from 1991 to mid 1999 based on samples sent for analysis of ACV concentration from various hospital departments in Sweden. Patients with neuropsychiatric symptoms (NS+, n=49) were compared with patients without symptoms (NS-, n=44). ACV and CMMG concentrations were analysed by HPLC. Medical records were analysed for symptoms and compared with pertinent cases identified from Medline. RESULTS: The serum CMMG levels were significantly higher in the NS+ group (mean=34.1 micro mol/l, 95% confidence interval 23.4-46.1) compared with the NS- group (mean=4.7 micro mol/l, 95% confidence interval 3.3-6.6; P<0.001). CMMG was the strongest predictor in a receiver-operating characteristics curve analysis (ROC), based on 77 patients, of ACV-related neuropsychiatric symptoms. The ROC curve for CMMG demonstrated that neuropsychiatric symptoms could be predicted with a sensitivity of 91% and a specificity of 93% with the use of a cut-off value of 10.8 micro mol/l of CMMG. Thirty-five of 49 patients in the NS+ group showed levels exceeding this concentration compared with only three of 44 of patients in the NS- group (P<0.001). ACV exposure, ACV concentration, creatinine clearance and creatinine concentration were weaker but statistically significant predictors. Haemodialysis reduced CMMG and ACV levels and relieved the symptoms. CONCLUSIONS: The determination of CMMG levels in serum may be a useful tool in supporting the diagnosis of ACV-associated neuropsychiatric symptoms. Furthermore, the monitoring of CMMG levels may prevent the emergence of symptoms.