Orosomucoid (alpha1-acid glycoprotein) plasma concentration and genetic variants: effects on human immunodeficiency virus protease inhibitor clearance and cellular accumulation

BACKGROUND AND OBJECTIVE: Protease inhibitors are highly bound to orosomucoid (ORM) (alpha1-acid glycoprotein), an acute-phase plasma protein encoded by 2 polymorphic genes, which may modulate their disposition. Our objective was to determine the influence of ORM concentration and phenotype on indinavir, lopinavir, and nelfinavir apparent clearance (CL(app)) and cellular accumulation. Efavirenz, mainly bound to albumin, was included as a control drug. METHODS: Plasma and cells samples were collected from 434 human immunodeficiency virus-infected patients. Total plasma and cellular drug concentrations and ORM concentrations and phenotypes were determined. RESULTS: Indinavir CL(app) was strongly influenced by ORM concentration (n = 36) (r2 = 0.47 [P = .00004]), particularly in the presence of ritonavir (r2 = 0.54 [P = .004]). Lopinavir CL(app) was weakly influenced by ORM concentration (n = 81) (r2 = 0.18 [P = .0001]). For both drugs, the ORM1 S variant concentration mainly explained this influence (r2 = 0.55 [P = .00004] and r2 = 0.23 [P = .0002], respectively). Indinavir CL(app) was significantly higher in F1F1 individuals than in F1S and SS patients (41.3, 23.4, and 10.3 L/h [P = .0004] without ritonavir and 21.1, 13.2, and 10.1 L/h [P = .05] with ritonavir, respectively). Lopinavir cellular exposure was not influenced by ORM abundance and phenotype. Finally, ORM concentration or phenotype did not influence nelfinavir (n = 153) or efavirenz (n = 198) pharmacokinetics. CONCLUSION: ORM concentration and phenotype modulate indinavir pharmacokinetics and, to a lesser extent, lopinavir pharmacokinetics but without influencing their cellular exposure. This confounding influence of ORM should be taken into account for appropriate interpretation of therapeutic drug monitoring results. Further studies are needed to investigate whether the measure of unbound drug plasma concentration gives more meaningful information than total drug concentration for indinavir and lopinavir.

Effects of induced parturition in goats on immunoglobulin G and chitotriosidase activity in colostrum and plasma and on plasma concentrations of prolactin

The effect of induction of parturition with a PGF(2)alpha analog on plasma concentration of prolactin (PRL) and its effects on colostrum concentration of IgG and chitotriosidase (ChT) activity were studied in 16 pregnant Majorera goats. Treated goats, those in which parturition was induced, had greater concentrations of PRL than control goats 24 h before parturition (P < 0.05) and 48 h after parturition (P < 0.05). Control goats had greater concentrations of PRL than treated goats 96 h after parturition (P < 0.05). Plasma concentration of IgG did not differ between groups during the experimental period, but colostrum concentrations of IgG were greater in control goats than in treated goats at parturition (P < 0.05). Plasma ChT activity decreased during the period 72 h before parturition to 24 h after parturition in control and treated goats. Time evolution after partum affected the colostrum ChT activity, being greater at parturition than after parturition in both groups (P < 0.05). In summary, concentration of IgG in colostrum is slightly diminished if parturition is induced. Induction of parturition causes an early increase in PRL, which is most likely responsible for preterm suppression of IgG transport into mammary secretions. (C) 2011 Elsevier Inc. All rights reserved.

Plasma and urine neutrophil gelatinase-associated lipocalin (NGAL) in dogs with acute kidney injury or chronic kidney disease.

BACKGROUND Neutrophil gelatinase-associated lipocalin (NGAL) is a protein that is used in human medicine as a real-time indicator of acute kidney injury (AKI). HYPOTHESIS Dogs with AKI have significantly higher plasma NGAL concentration and urine NGAL-to-creatinine ratio (UNCR) compared with healthy dogs and dogs with chronic kidney disease (CKD). ANIMALS 18 healthy control dogs, 17 dogs with CKD, and 48 dogs with AKI. METHODS Over a period of 1 year, all dogs with renal azotemia were prospectively included. Urine and plasma samples were collected during the first 24 hours after presentation or after development of renal azotemia. Plasma and urine NGAL concentrations were measured with a commercially available canine NGAL Elisa Kit (Bioporto® Diagnostic) and UNCR was calculated. A single-injection plasma inulin clearance was performed in the healthy dogs. RESULTS Median (range) NGAL plasma concentration in healthy dogs, dogs with CKD, and AKI were 10.7 ng/mL (2.5-21.2), 22.0 ng/mL (7.7-62.3), and 48.3 ng/mL (5.7-469.0), respectively. UNCR was 2 × 10(-8) (0-46), 1,424 × 10(-8) (385-18,347), and 2,366 × 10(-8) (36-994,669), respectively. Dogs with renal azotemia had significantly higher NGAL concentrations and UNCR than did healthy dogs (P < .0001 for both). Plasma NGAL concentration was significantly higher in dogs with AKI compared with dogs with CKD (P = .027). CONCLUSIONS AND CLINICAL IMPORTANCE Plasma NGAL could be helpful to differentiate AKI from CKD in dogs with renal azotemia.

Clinical usefulness of therapeutic concentration monitoring for imatinib dosage individualization: results from a randomized controlled trial.

PURPOSE This study assessed whether a cycle of "routine" therapeutic drug monitoring (TDM) for imatinib dosage individualization, targeting an imatinib trough plasma concentration (C min) of 1,000 ng/ml (tolerance: 750-1,500 ng/ml), could improve clinical outcomes in chronic myelogenous leukemia (CML) patients, compared with TDM use only in case of problems ("rescue" TDM). METHODS Imatinib concentration monitoring evaluation was a multicenter randomized controlled trial including adult patients in chronic or accelerated phase CML receiving imatinib since less than 5 years. Patients were allocated 1:1 to "routine TDM" or "rescue TDM." The primary endpoint was a combined outcome (failure- and toxicity-free survival with continuation on imatinib) over 1-year follow-up, analyzed in intention-to-treat (ISRCTN31181395). RESULTS Among 56 patients (55 evaluable), 14/27 (52 %) receiving "routine TDM" remained event-free versus 16/28 (57 %) "rescue TDM" controls (P = 0.69). In the "routine TDM" arm, dosage recommendations were correctly adopted in 14 patients (median C min: 895 ng/ml), who had fewer unfavorable events (28 %) than the 13 not receiving the advised dosage (77 %; P = 0.03; median C min: 648 ng/ml). CONCLUSIONS This first target concentration intervention trial could not formally demonstrate a benefit of "routine TDM" because of small patient number and surprisingly limited prescriber's adherence to dosage recommendations. Favorable outcomes were, however, found in patients actually elected for target dosing. This study thus shows first prospective indication for TDM being a useful tool to guide drug dosage and shift decisions. The study design and analysis provide an interesting paradigm for future randomized TDM trials on targeted anticancer agents.

Assessing the efficiency of a pharmacokinetic-based algorithm for target-controlled infusion of ketamine in ponies

The objective of this study was to assess a pharmacokinetic algorithm to predict ketamine plasma concentration and drive a target-controlled infusion (TCI) in ponies. Firstly, the algorithm was used to simulate the course of ketamine enantiomers plasma concentrations after the administration of an intravenous bolus in six ponies based on individual pharmacokinetic parameters obtained from a previous experiment. Using the same pharmacokinetic parameters, a TCI of S-ketamine was then performed over 120 min to maintain a concentration of 1 microg/mL in plasma. The actual plasma concentrations of S-ketamine were measured from arterial samples using capillary electrophoresis. The performance of the simulation for the administration of a single bolus was very good. During the TCI, the S-ketamine plasma concentrations were maintained within the limit of acceptance (wobble and divergence <20%) at a median of 79% (IQR, 71-90) of the peak concentration reached after the initial bolus. However, in three ponies the steady concentrations were significantly higher than targeted. It is hypothesized that an inaccurate estimation of the volume of the central compartment is partly responsible for that difference. The algorithm allowed good predictions for the single bolus administration and an appropriate maintenance of constant plasma concentrations.

Garlic extract induces intestinal P-glycoprotein, but exhibits no effect on intestinal and hepatic CYP3A4 in humans

Garlic extracts have been shown to decrease drug exposure for saquinavir, a P-glycoprotein and cytochrome P450 3A4 substrate. In order to explore the underlying mechanisms and to study the effects of garlic on pre-systemic drug elimination, healthy volunteers were administered garlic extract for 21 days. Prior to and at the end of this period, expression of duodenal P-glycoprotein and cytochrome P450 3A4 protein were assayed and normalized to villin, while hepatic cytochrome P450 3A4 function and simvastatin, pravastatin and saquinavir pharmacokinetics were also evaluated. Ingestion of garlic extract increased expression of duodenal P-glycoprotein to 131% (95% CI, 105-163%), without increasing the expression of cytochrome P450 3A4 which amounted to 87% (95% CI, 67-112%), relative to baseline in both cases. For the erythromycin breath test performed, the average result was 96% (95% CI, 83-112%). Ingestion of garlic extract had no effect on drug and metabolite AUCs following a single dose of simvastatin or pravastatin, although the average area under the plasma concentration curve (AUC) of saquinavir decreased to 85% (95% CI, 66-109%), and changes in intestinal P-glycoprotein expression negatively correlated with this change. In conclusion, garlic extract induces intestinal expression of P-glycoprotein independent of cytochrome P450 3A4 in human intestine and liver.

Oral voclosporin: novel calcineurin inhibitor for treatment of noninfectious uveitis

Voclosporin, a novel immunomodulatory drug inhibiting the calcineurin enzyme, was developed to prevent organ graft rejection and to treat autoimmune diseases. The chemical structure of voclosporin is similar to that of cyclosporine A, with a difference in one amino acid, leading to superior calcineurin inhibition and less variability in plasma concentration. Compared with placebo, voclosporin may significantly reduce inflammation and prevent recurrences of inflammation in patients with noninfectious uveitis. Future studies have to show if these advantages are accompanied by greater clinical efficacy and fewer side effects compared with the classic calcineurin inhibitors.

Induced hypoglycemia for 48 hours indicates differential glucose and insulin effects on liver metabolism in dairy cows

Hypoglycemia is a characteristic condition of early lactation dairy cows and is subsequently dependent on, and may affect, metabolism in the liver. The objective of the present study was to investigate the effects of induced hypoglycemia, maintained for 48 h, on metabolic parameters in plasma and liver of mid-lactation dairy cows. The experiment involved 3 treatments, including a hyperinsulinemic hypoglycemic clamp (HypoG, n=6) to obtain a glucose concentration of 2.5 mmol/L, a hyperinsulinemic euglycemic clamp (EuG, n=6) in which the effect of insulin was studied, and a control treatment with a 0.9% saline solution (NaCl, n=6). Blood samples for measurements of insulin, metabolites, and enzymes were taken at least once per hour. Milk yield was recorded and milk samples were collected before and after treatment. Liver biopsies were obtained before and after treatment to measure mRNA abundance by real-time, quantitative reverse transcription-PCR of 12 candidate genes involved in the main metabolic pathways. Milk yield decreased in HypoG and NaCl cows, whereas it remained unaffected in EuG cows. Energy-corrected milk yield (kg/d) was only decreased in HypoG cows. In plasma, concentration of beta-hydroxybutyrate decreased in response to treatment in EuG cows and was lower (0.41+/-0.04 mmol/L) on d 2 of the treatment compared with that in HypoG and NaCl cows (on average 0.61+/-0.03 mmol/L, respectively). Nonesterified fatty acids remained unaffected in all treatments. In the liver, differences between treatments for their effects were only observed in case of mitochondrial phosphoenolpyruvate carboxykinase (PEPCKm) and glucose-6-phosphatase (G6PC). In HypoG, mRNA abundance of PEPCKm was upregulated, whereas in EuG and NaCl cows, it was downregulated. The EuG treatment downregulated mRNA expression of G6PC, a marked effect compared with the unchanged transcript expression in NaCl. The mRNA abundance of the insulin receptor remained unaffected in all treatments, and no significant treatment differences were observed for genes related to lipid metabolism. In conclusion, low glucose concentrations in dairy cows affect liver metabolism at a molecular level through upregulation of PEPCKm mRNA abundance. Metabolic regulatory events in the liver are directed, apart from hormones, by the level of metabolites, either in excess (e.g., free fatty acids) or in shortage (e.g., glucose).

Ondansetron does not reduce the shivering threshold in healthy volunteers

BACKGROUND: Ondansetron, a serotonin-3 receptor antagonist, reduces postoperative shivering. Drugs that reduce shivering usually impair central thermoregulatory control, and may thus be useful for preventing shivering during induction of therapeutic hypothermia. We determined, therefore, whether ondansetron reduces the major autonomic thermoregulatory response thresholds (triggering core temperatures) in humans. METHODS: Control (placebo) and ondansetron infusions at the target plasma concentration of 250 ng ml(-1) were studied in healthy volunteers on two different days. Each day, skin and core temperatures were increased to provoke sweating; then reduced to elicit peripheral vasoconstriction and shivering. We determined the core-temperature sweating, vasoconstriction and shivering thresholds after compensating for changes in mean-skin temperature. Data were analysed using t-tests and presented as means (sds); P<0.05 was taken as significant. RESULTS: Ondensetron plasma concentrations were 278 (57), 234 (55) and 243 (58) ng ml(-1) at the sweating, vasoconstriction and shivering thresholds, respectively; these corresponded to approximately 50 mg of ondansetron which is approximately 10 times the dose used for postoperative nausea and vomiting. Ondansetron did not change the sweating (control 37.4 (0.4) degrees C, ondansetron 37.6 (0.3) degrees C, P=0.16), vasoconstriction (37.0 (0.5) degrees C vs 37.1 (0.3) degrees C; P=0.70), or shivering threshold (36.3 (0.5) degrees C vs 36.3 (0.6) degrees C; P=0.76). No sedation was observed on either study day. CONCLUSIONS: /b>. Ondansetron appears to have little potential for facilitating induction of therapeutic hypothermia.

Continuous or repeated prolonged cisplatin infusions in children: a prospective study on ototoxicity, platinum concentrations, and standard serum parameters

BACKGROUND: To overcome the ototoxicity of cisplatin, single bolus infusions were replaced by repeated prolonged infusions of lower doses or by continuous infusions at still lower infusion rates. However, considering ototoxicity little is, in fact, known about the tolerance of repeated prolonged or continuous infusion in children. PROCEDURE: Auditory function was monitored along with plasma concentrations of free and total platinum (Pt), and with standard serum parameters (sodium, potassium, calcium, magnesium, phosphate, chloride, and creatinine) in 24 children receiving cisplatin by continuous infusion for the treatment of neuroblastoma and osteosarcoma or by repeated 1 or 6 hr infusions for the treatment of germ cell tumors. RESULTS: Hearing deteriorated in 10/15 osteosarcoma patients, 2/3 neuroblastoma patients, and 1/6 patients with germ cell tumors. Ototoxicity occurred after cumulative doses between 120 and 360 mg/m(2) cisplatin. In osteosarcoma patients, ototoxicity was associated with a comparatively higher mean plasma concentration of free Pt. However, Pt plasma concentrations did not discriminate between patients with or without ototoxicity. In patients experiencing ototoxicity serum creatinine increased by 45% compared to pre-treatment levels (mean). Serum creatinine increased by 26% in patients without ototoxicity (P < 0.05, Mann-Whitney Rank sum test). Despite standardized hydration, discrete but significant changes of potassium, sodium, magnesium, and phosphate were observed during and/or after cisplatin infusion, which, however, did not discriminate between patients with and without ototoxicity. CONCLUSIONS: While continuous cisplatin infusions are less nephrotoxic than repeated prolonged infusions, we observed considerable ototoxicity in patients treated with continuous cisplatin infusions, which necessitates further evaluations on the tolerance of continuous cisplatin infusions in children.

How much is too much? Oligosymptomatic presentation after 11.5 g of diphenhydramine

We report the case of a 47-year-old male obese Caucasian patient presenting 2 hours after ingestion of 11.5 g of diphenhydramine. Despite this excessive overdose, he showed only a few hours of impaired consciousness and no further symptoms. A diphenhydramine plasma concentration of 15,352 nmol/L was measured 8 hours after the overdose ingestion. A heterogeneous CYP2D6 extensive metabolizer genotype excludes a pharmacokinetic explanation for this unusually oligosymptomatic presentation. However, the patient suffered from longstanding, refractory depression despite numerous treatment attempts with various drugs, pointing to the possibility of decreased pharmacodynamic responsiveness for therapeutic and toxic effects.

Oral diacetylmorphine (heroin) yields greater morphine bioavailability than oral morphine: bioavailability related to dosage and prior opioid exposure

AIMS: In the Swiss heroin substitution trials, patients are treated with self-administered diacetylmorphine (heroin). Intravenous administration is not possible in patients that have venosclerosis. Earlier studies have demonstrated that oral diacetylmorphine may be used, although it is completely converted to morphine presystemically. Morphine bioavailability after high-dose oral diacetylmorphine is considerably higher than would be predicted from low-dose trials. The aim was to investigate whether the unexpectedly high bioavailability is due to a difference in the drug examined, and whether it depends on previous exposure or on dose. METHODS: Opioid-naive healthy volunteers and dependent patients from the Swiss heroin trials (n = 8 per group) received low doses of intravenous and oral deuterium-labelled morphine and diacetylmorphine, respectively. Patients also received a high oral diacetylmorphine dose. RESULTS: The maximum plasma concentration (C(max)) of morphine was twofold higher after oral diacetylmorphine than after morphine administration in both groups. However, morphine bioavailability was considerably higher in chronic users [diacetylmorphine 45.6% (95% confidence interval 40.0, 51.3), morphine 37.2% (30.1, 44.3)] than in naive subjects [diacetylmorphine 22.9% (16.4, 29.4), morphine 23.9% (16.5, 31.2)] after low oral doses (48.5 micromol) of either diacetylmorphine or morphine. Morphine clearance was similar in both groups. Moreover, oral absorption of morphine from diacetylmorphine was found to be dose dependent, with bioavailability reaching 64.2% (55.3, 73.1) for high diacetylmorphine doses (1601 micromol). CONCLUSIONS: Oral absorption of opioids is substance-, dose- and patient collective-dependent, suggesting that there may be a saturation of first-pass processes, the exact mechanism of which is not yet understood.

Oral melatonin reduces blood coagulation activity: a placebo-controlled study in healthy young men

Melatonin has previously been suggested to affect hemostatic function but studies on the issue are scant. We hypothesized that, in humans, oral administration of melatonin is associated with decreased plasma levels of procoagulant hemostatic measures compared with placebo medication and that plasma melatonin concentration shows an inverse association with procoagulant measures. Forty-six healthy men (mean age 25 +/- 4 yr) were randomized, single-blinded, to either 3 mg of oral melatonin (n = 25) or placebo medication (n = 21). One hour thereafter, levels of melatonin, fibrinogen, and D-dimer as well as activities of coagulation factor VII (FVII:C) and VIII (FVIII:C) were measured in plasma. Multivariate analysis of covariance and regression analysis controlled for age, body mass index, mean arterial blood pressure, heart rate, and norepinephrine plasma level. Subjects on melatonin had significantly lower mean levels of FVIII:C (81%, 95% CI 71-92 versus 103%, 95% CI 90-119; P = 0.018) and of fibrinogen (1.92 g/L, 95% CI 1.76-2.08 versus 2.26 g/L, 95% CI 2.09-2.43; P = 0.007) than those on placebo explaining 14 and 17% of the respective variance. In all subjects, increased plasma melatonin concentration independently predicted lower levels of FVIII:C (P = 0.037) and fibrinogen (P = 0.022) explaining 9 and 11% of the respective variance. Melatonin medication and plasma concentration were not significantly associated with FVII:C and D-dimer levels. A single dose of oral melatonin was associated with lower plasma levels of procoagulant factors 60 min later. There might be a dose-response relationship between the plasma concentration of melatonin and coagulation activity.

The pharmacokinetic profile of fesoterodine: similarities and differences to tolterodine

BACKGROUND: Fesoterodine is a new antimuscarinic agent developed for the treatment of overactive bladder. Fesoterodine itself is inactive and is rapidly and extensively converted by ubiquitous esterases to its principal active moiety, 5-hydroxymethyl tolterodine (5-HMT). 5-HMT is formed via biotransformation of both fesoterodine and tolterodine, albeit by different metabolising enzymes, viz. esterases and CYP2D6 respectively. Tolterodine is a potent muscarinic receptor antagonist and has been used for the treatment of overactive bladder for over ten years. The objective of this study was to establish the pharmacokinetic profile of fesoterodine and to highlight ist potential pharmacokinetic advantages over tolterodine. DESIGN: Single-centre, open-label, randomised, 4-way crossover study in a total of 24 healthy male volunteers. Single oral doses of 4, 8, or 12 mg fesoterodine were administered after an overnight fast. In addition, the 8 mg dose was also administered after a standard high-fat and high-calorie breakfast. Blood and urine samples for the analysis of 5-HMT were collected before and multiple times after drug administration for pharmacokinetic analysis. RESULTS: The mean peak plasma concentration (Cmax) of 5-HMT and the mean area under the time versus concentration curve (AUC) increased proportionally with the fesoterodine dose. These two parameters were some 2-fold higher in CYP2D6 poor metabolisers, whereas the time to peak plasma concentration (tmax) and half life (t1/2) were not influenced by the dose or the CYP2D6 metaboliser status. If fesoterodine was taken following a high-fat breakfast, we observed small increases in Cmax and AUC. In spite of these modest genetic influences and food effects on the pharmacokinetics of fesoterodine, the overall interindividual variability in Cmax levels was relatively little compared to previously published reports using tolterodine. CONCLUSIONS: Due to the esterase-mediated cytochrome P450-independent formation of 5-HMT and involvement of multiple metabolic and renal excretion pathways in the elimination of 5-HMT, the effects of patient-intrinsic and -extrinsic factors on the pharmacokinetics of fesoterodine are only modest, with some 2-fold higher 5-HMT exposure. Therefore, in contrast to tolterodine, no reduction of fesoterodine dosage is required under conditions of reduced elimination. In most cases of drug interaction or renal/hepatic impairment, the fesoterodine dose may be increased to 8 mg/day based on individual patients' response, or patients may be required to remain at the initial recommended dose of 4 mg/day.