Steady-state Plasma Drug Concentrations Research Articles

The pharmacokinetics of single oral dose extended-release topiramate and adverse effects after multi-dose administration in healthy cats.

Current treatment options for feline epilepsy are limited to medications that require administration of multiple doses per day or administration of a capsule or large tablet. Expanding the current treatment options could improve patient and owner compliance and optimize seizure control. Topiramate has been used sparingly in veterinary medicine, and limited pharmacokinetic studies have focused on immediate release formulations in dogs. If effective and safe, topiramate extended-release (XR) could broaden the current treatment options for feline epilepsy. The aims of this two-phase study were to establish single-dose pharmacokinetics for topiramate XR in cats, identify a dosing regimen that maintains steady-state plasma drug concentrations within a reference range extrapolated from human medicine (5-20 μg/mL), and evaluate the safety of topiramate XR in cats following multidose administration. Topiramate XR administered orally at 10mg/kg once daily for 30 days was sufficient to achieve the desired concentrations in all cats. While no clinically apparent adverse effects were observed, four out of eight cats developed subclinical anemia, calling into question the safety of topiramate XR with chronic administration. Further studies are necessary to better understand the potential adverse effects and overall efficacy of topiramate XR for the treatment of feline epilepsy.

Pharmacokinetics of a FDA-labeled dose of diclazuril administered orally once weekly to adult horses

Equine protozoal myeloencephalitis (EPM) has remained a devastating neurological disease of the Americas, especially in young performance horses. Prophylactic treatment strategies with diclazuril have shown to reduce seroprevalence and titer levels to Sarcocystis neurona in healthy horses continuously exposed to the apicomplexan parasite. The goal of this study was to determine if the FDA-labeled dose of 1 mg/kg of 1.56% diclazuril (ProtazilTM) given once weekly to healthy adult horses would achieve steady-state concentrations in plasma known to be inhibitory to S. neurona in cell culture. Five individual diclazuril doses were administered at weekly intervals to 8 adult horses. Blood was collected via venipuncture immediately before (trough concentration) and 10 hours after (peak concentration) each diclazuril administration. Following the fifth dose, additional blood samples were collected every 24 hours after the peak blood collection for 7 days. All plasma samples were analyzed by high-pressure liquid chromatography. The pharmacokinetic analysis was performed using a nonlinear mixed effects model. The mean population-derived peak concentration was 264 ng/mL and the mean terminal half-life was 3.6 days. Thus, the oral administration of an FDA-labeled dose of diclazuril to healthy horses once a week was able to produce steady-state plasma drug concentrations known to inhibit S. neurona in vitro.

A Reevaluation of Prazosin Pharmacokinetics in a Two-Compartment Model, the Apparent Volume of Distribution and Comparative Simulations in the One-Compartment Model

Published clinical data of Prazosin were reevaluated pharmacokinetically using explicit solutions to drug concentration as a function of total time for IV bolus injection, intermittent intravenous infusion and oral routes of administration in an open two-compartment model. In a novel way, the apparent volume of distribution was estimated from a two-compartment model and found to be close to the total body water suggesting that Prazosin is distributed in all tissues both extracellularly and intracellularly. In addition, extracting the value of the apparent volume of distribution from a two-compartment model allowed comparative simulations in the one-compartment model. It is shown that dosage calculations of Prazosin intermittent infusion can be safely performed using the simpler one-compartment model equations. Lastly, several additional time-dependent pharmacokinetic parameters e.g., the peak time in the central and peripheral compartment and non-steady state and steady state peak concentration and AUC were determined using series equations for all three routes of administration, as a function of dose number and total time upon multiple drug administrations in the two-compartment model. It is also the first time that steady-state plasma drug concentration equations were derived in a two-compartment mammillary model.

Influence of FMO3 and CYP3A4 Polymorphisms on the Pharmacokinetics of Teneligliptin in Humans.

Teneligliptin, a dipeptidyl peptidase-4 inhibitor, is used to treat type 2 diabetes mellitus. FMO3 and CYP3A4 metabolize teneligliptin into teneligliptin sulfoxide. This study examined the effects of FMO3 (rs909530, rs1800822, rs2266780, and rs2266782) and CYP3A4 (rs2242480) polymorphisms on teneligliptin pharmacokinetics at a steady state among 23 healthy participants administered 20 mg teneligliptin daily for 6 days. Subjects with FMO3 rs909530, rs2266780, and rs2266782 polymorphisms exhibited a significant gene dosage-dependent increase in maximum steady-state plasma drug concentration (Cmax,ss) and area under the drug concentration vs time curve (AUC) (p<0.05). However, the Cmax values significantly decreased but the AUC values did not significantly vary in subjects with CYP3A4 polymorphism (rs2242480). These results suggest that FMO3 and CYP3A4 polymorphisms affect teneligliptin pharmacokinetics in humans. The findings of this study provide a scientific basis for the inter-individual variation in teneligliptin disposition.

3D-Tissue Engineered Bone Marrow (3DTEBM) Culture Predicts Clinical Efficacy of Drugs Better Than Regular Culture Systems in Multiple Myeloma

Purpose: The second most common hematological malignancy, Multiple Myeloma (MM), continues to be a fatal disease even with the development of novel therapies. Despite promising preclinical data in standard two-dimensional (2D) models, most phase 3 clinical oncology trials fail. This highlights the potential discrepancy between the current in vitro models, the pathophysiology of the disease in the patients, and the urgent need for better in vitro models for drug development and improved prediction of efficacy in patients. We have previously developed a 3D-Tissue Engineered Bone Marrow culture (3DTEBM), which showed superior properties for proliferation of primary MM cells over weeks in culture, derived from the BM of MM patients, including MM cells, other cells in the BM microenvironment, and BM supernatant. In this study, we found that the 3DTEBM model provides better prediction of clinical efficacy as compared to regular tissue cultures.Methods: We performed a literature search that examined the efficacious concentrations of drugs used for the treatment of MM, in vitro and in patients. We defended the efficacious clinical as the steady state plasma drug concentration (Css), and the efficacious in vitro concentration as the half maximal inhibitory concentration (IC50) of 11 drugs used in MM (Carfilzomib, Bortezomib, Ixazomib, Panobinostat, Lenalidomide, Pomalidomide, Dexamethasone, Etoposide, Doxorubicin, Cytoxan, and Melphalan). The Css and IC50 of each drug were calculated from the average of multiple papers (at least 3 values for each), and the correlation between the IC50 and the Css (both obtained from the literature) was tested.Moreover, we tested the efficacy of the drugs in the 3DTEBM by treating MM cells with increasing concentrations of the different drugs (unique range for each drug); thus, the IC50 for each drug in the 3DTEBM was established. Correlation between the IC50 (obtained experimentally in the 3DTEBM) and the Css (obtained from the literature) was then tested.Results: There was no correlation between the in vitro IC50 values from the classic 2D culture systems (based on literature) and the efficacious clinical concentrations (Css), with a correlation coefficient of R2=0.007. In contrast, the in vitro IC50 values obtained experimentally in the 3DTEBM directly correlated with the efficacious clinical concentrations (Css), with a correlation coefficient of R2=0.979.Conclusions: The 3DTEBM model predicts clinical efficacy of drugs better than regular culture systems in multiple myeloma, and can provide a more pathophysiologically relevant model for preclinical drug development and development of clinical personalized medicine treatment plans in multiple myeloma. DisclosuresJeske:Cellatrix LLC: Employment. Azab:Tioma: Research Funding; Verastem: Research Funding; Cellatrix LLC: Other: Founder and owner; Karyopharm: Research Funding; Targeted Therapeutics LLC: Other: Founder and owner; Selexys: Research Funding; Cell Works: Research Funding; Abbvie: Research Funding; Cleave Bioscience: Research Funding; Glycomimetics: Research Funding.

Changes in serum concentration of rilpivirine in an HIV-infected patient treated with a combination therapy of hemodialysis and peritoneal dialysis

BackgroundTo our knowledge, there are no preexisting reports concerning rilpivirine (RPV) removal by hemodialysis and peritoneal dialysis.Case presentationThis study aimed to evaluate the effect of hemodialysis and peritoneal dialysis on plasma concentrations of RPV in a 45-year-old man infected with HIV and exhibiting end-stage renal disease (ESRD). The extraction ratio of RPV by hemodialysis was 4.5%. Plasma concentrations of RPV remained far above the protein-binding-adjusted inhibitory levels during a combination therapy of hemodialysis and peritoneal dialysis. Our results suggest minimal RPV removal via hemodialysis and peritoneal dialysis with no specific dosage adjustments required in an HIV-infected patient undergoing this combination therapy.ConclusionIn conclusion, this study showed that RPV administered without dose adjustment resulted in steady-state plasma drug concentration in an HIV-infected patient treated with a combination therapy of hemodialysis and peritoneal dialysis.

Current Status and Challenges in Rotigotine Delivery.

Rotigotine is a non-ergoline, high lipophilic dopamine agonist. It is indicated as the first-line therapy for Parkinson's disease (PD) and Restless Leg Syndrome (RLS). However, the precise mechanism of rotigotine is yet to be known. Rotigotine has similar safety and tolerability to the other oral non-ergolinic dopamine antagonists in clinical trials, which include nausea, dizziness and somnolence. Neupro® was the first marketed transdermal patch formulation having rotigotine. The transdermal delivery system is advantageous as it enables continuous administration of the drug, thus providing steady-state plasma drug concentration for 24-hours. Intranasal administration of rotigotine allows the drug to bypass the blood-brain barrier enabling it to reach the central nervous system within minutes. Rotigotine can also be formulated as an extended-release microsphere for injection. Some challenges remain in other routes of rotigotine administration such as oral, parenteral and pulmonary, whereby resolving these challenges will be beneficial to patients as they are less invasive and comfortable in terms of administration. This review compiles recent work on rotigotine delivery, challenges and its future perspective.

Contemporaneous management of ampicillin infusions in the outpatient setting through the use of therapeutic drug monitoring

The use of ampicillin in the outpatient setting has traditionally been avoided because of the short half-life and instability in solution of this drug. However, recent in vitro data and two case series support the safe and effective administration of ampicillin by continuous infusion in the community. Therapeutic drug monitoring (TDM) of beta-lactam antibiotics can be used to optimise antibiotic exposure and ensure adequate clinical responses. A case series is presented of patients receiving ampicillin via prolonged infusion in the outpatient setting, with TDM to ensure adequate plasma antibiotic levels were achieved.Three patients who received ampicillin by continuous infusion under the Outpatient Parenteral Antimicrobial Therapy (OPAT) program are described, including details of antibiotic dose and steady-state plasma drug concentration as measured by high-performance liquid chromatography. All three patients had an infection with ampicillin-susceptible Enterococcus faecalis; one patient had post-partum endometritis, one had urosepsis and one had a complex polymicrobial bone and joint infection.Adequate plasma drug levels were achieved in all patients. Management of the antibiotic temperature and infusion times, and appropriate timing of drug levels in the community were required. Two patients achieved clinical cure, while the third required further surgical debridement and antibiotic therapy.TDM in this setting enabled the contemporaneous management and dose alteration of ampicillin. Ampicillin may be a safe and effective drug when administered by continuous infusion with appropriate TDM in the community setting.

Diclazuril nonlinear mixed-effects pharmacokinetic modelling of plasma concentrations after oral administration to adult horses every 3–4 days

The purpose of this study was to determine if a low dose of diclazuril (0.5mg/kg of 1.56% diclazuril pellets) given to six healthy adult horses every 3–4 days for a total of five administrations would achieve steady-state plasma concentrations known to be inhibitory to Sarcocystis neurona and Neospora caninum. Blood was collected via venipuncture immediately before (trough concentrations) and 10h after (peak concentrations) each diclazuril administration and analysed by high-pressure liquid chromatography. The mean population-derived peak concentration was 0.284μg/mL and the mean terminal half-life was 1.6 days, but with a large variation. Thus, low dose diclazuril pellets produce steady-state plasma drug concentrations known to inhibit S. neurona (0.001μg/mL) and N. caninum (0.1μg/mL).

Quantitative prediction of human pharmacokinetics and pharmacodynamics of imigliptin, a novel DPP-4 inhibitor, using allometric scaling, IVIVE and PK/PD modeling methods

PurposeTo predict the pharmacokinetic/pharmacodynamic (PK/PD) profiles of imigliptin, a novel DPP-4 inhibitor, in first-in-human (FIH) study based on the data from preclinical species. MethodsImigliptin was intravenously and orally administered to rats, dogs, and monkeys to assess their PK/PD properties. DPP-4 activity was the PD biomarker. PK/PD profiles of sitagliptin and alogliptin in rats and humans were obtained and digitized from literatures. PK/PD profiles of all dose levels for each drug in each species were analyzed using modeling approach. Human CL, Vss and PK profiles of imigliptin were then predicted using Allometric Scaling (AS), in vitro in vivo extrapolation (IVIVE), and the steady-state plasma drug concentration – mean residence time (Css-MRT) methods. In vitro EC50 corrected by fu and in vivo EC50 in rats corrected by interspecies difference of sitagliptin and alogliptin were utilized separately to predict imigliptin human EC50. The prediction by integrating all above methods was evaluated by comparing observed and simulated PK/PD profiles in healthy subjects. ResultsFull PK/PD profiles in animal were summarized for imigliptin, sitagliptin and alogliptin. Imigliptin CL, Vss, and Fa were predicted to be 19.1L/h, 247L, and 0.81 in humans, respectively. Predicted imigliptin AUCs, AUECs, and Emax in humans were within 0.8–1.2 times of observed values whereas other predicted PK/PD parameters were within 0.5–1.5 times of observed values. ConclusionsBy integrating available preclinical and clinical data, FIH PK/PD profiles of imigliptin could be accurately predicted.

Penetration of antimicrobials to pulmonary epithelial lining fluid and muscle and impact of drug physicochemical properties determined by microdialysis

IntroductionThe objectives of this study were to characterize antimicrobial drug penetration into the pulmonary epithelial lining fluid (PELF) and extracellular fluid (ECF) of muscle in relation to physicochemical properties of the drugs (molecular mass, Log D, polar surface area and charge), using intrabronchial microdialysis. The series of drugs tested include gentamicin, sulfadiazine, cefquinome, minocycline and colistin. MethodsDrug concentrations were measured during 2h of steady state plasma drug concentrations at therapeutic levels in anesthetized pigs. Microdialysis probes were positioned 2 to 4cm distal to the tracheal bifurcature and in M. gluteobiceps and were calibrated by retrodialysis by drug. ResultsMean AUCPELF/PLASMA(fu) and mean AUCMUSCLE/PLASMA(fu) ratios were respectively for gentamicin (0.8, 0.7), sulfadiazine (1.1, 0.7), cefquinome (1.3, 1.5) minocycline (1.6, 0.7) and colistin (0.26, 0.12). The penetration of drugs into PELF (r2=0.55–0.77, p=0.0004–0.0089) and ECF of muscle (r2=0.39–0.53, p=0.0108–0.0397) was positively correlated to Log D, whereas molecular mass, polar surface area and charge were negatively correlated to drug penetration. Sulfadiazine, gentamicin, cefquinome and colistin had similar penetration ratios into PELF and ECF of muscle, ranging from 0.12 to 1.50. DiscussionIn conclusion, drug penetration into PELF and ECF of muscle is correlated to mass, lipophilicity, polarity and charge of the drugs. Drug partition into ECF of muscle and PELF are similar for the passively transported drugs gentamicin, sulfadiazine, cefquinome and colistin, whereas minocycline appears to be actively transported into PELF.

An update on pharmacological, pharmacokinetic properties and drug-drug interactions of rotigotine transdermal system in Parkinson's disease and restless legs syndrome.

This narrative review reports on the pharmacological and pharmacokinetic properties of rotigotine, a non-ergolinic D3/D2/D1 dopamine receptor agonist approved for the treatment of early- and advanced-stage Parkinson’s disease (PD) and moderate to severe restless legs syndrome (RLS). Rotigotine is formulated as a transdermal patch providing continuous drug delivery over 24 h, with a plasma concentration profile similar to that of administration via continuous intravenous infusion. Absolute bioavailability after 24 h transdermal delivery is 37 % of the applied rotigotine dose. Following a single administration of rotigotine transdermal system (24-h patch-on period), most of the absorbed drug is eliminated in urine and feces as sulphated and glucuronidated conjugates within 24 h of patch removal. The drug shows a high apparent volume of distribution (>2500 L) and a total body clearance of 300–600 L/h. Rotigotine transdermal system provides dose-proportional pharmacokinetics up to supratherapeutic dose rates of 24 mg/24 h, with steady-state plasma drug concentrations attained within 1–2 days of daily dosing. The pharmacokinetics of rotigotine transdermal patch are similar in healthy subjects, patients with early- or advanced-stage PD, and patients with RLS when comparing dose-normalized area under the plasma concentration–time curve (AUC) and maximum plasma drug concentration (C max), as well as half-life and other pharmacokinetic parameters. Also, it is not influenced in a relevant manner by age, sex, ethnicity, advanced renal insufficiency, or moderate hepatic impairment. No clinically relevant drug–drug interactions were observed following co-administration of rotigotine with levodopa/carbidopa, domperidone, or the CYP450 inhibitors cimetidine or omeprazole. Also, pharmacodynamics and pharmacokinetics of an oral hormonal contraceptive were not influenced by rotigotine co-administration. Rotigotine was generally well tolerated, with an adverse event profile consistent with dopaminergic stimulation and use of a transdermal patch. These observations, combined with the long-term efficacy demonstrated in clinical studies, support the use of rotigotine as a continuous non-ergot D3/D2/D1 dopamine receptor agonist in the treatment of PD and RLS.

Evaluation of &lt;i&gt;In vitro&lt;/i&gt; and &lt;i&gt;In vivo&lt;/i&gt; Performance of Granisetron In situ Forming Implants: Effect of Sterilization, Storage Condition and Degradation

Purpose: To investigate the effect of various solvent systems and gamma irradiation on the in vitro and in vivo performance of granisetron HCl injectable phase-sensitive in situ forming implants (ISFIs).Methods: ISFIs were prepared by mixing and sterilized by gamma irradiation. Effect of solvent system was studied. Injectability, polymer degradation and stability studies (4 and 25 oC for 4 months), viscositymeasurements, as well as in vitro and in vivo (in rabbits) drug release, and also histological examinations for biocompatibility studies (in rabbits and rats) were carried out.Results: ISFIs showed good injectability from 20-gauge needle and their in vitro drug release increased in the following rank order of solvent/solvent combinations: dimethylsulphoxide (DMSO) &gt; DMSO:prophylenecarbonate (PC) &gt; DMSO:triacetin(TA) &gt; DMSO:benzylbenzoate (BB). DMSO:PC incorporating ISFI gave zero order (r2 = 0.9503) drug release for 21 days; application of gamma irradiation accelerated drug release with a difference factor (f1) of 53 but zero order release (r2 = 9690) was maintained. Following test results for DMSO:PC including ISFI as decrease in molecular weight of polymer was descriptive for drug release behavior and sterilization effect, additionally dynamic viscosities decreased in line with polymer degradation and all forms of this ISFI showed plastic flow(fresh, irradiated, aged at 4 and 25 oC for 4 months). In vivo performance showed steady state plasma drug concentrations between 2 to 21 days with value of 0.55 ± 0.03 ìg/ml and biocompatibility was confirmed by histological results obtained at specific stages of tissue reactions, and also by lack of fibrous capsule formation.Conclusion: An ISFI for long-term antiemetic therapy achieved in this preliminary study is promising and, therefore, further investigations are required.Keywords: Implant, Poly(DL-lactide-co-glycolide), Granisetron, Gamma irradiation, Sterilization, Degradation, Viscosity, Stability, Pharmacokinetic, Biocompatibility.

Chronic ethanol use in alcoholic beverages by HIV-infected patients affects the therapeutic window of stavudine, lamivudine and nevirapine during the 9-month follow-up period: using chronic alcohol-use biomarkers.

Abstract Background: Chronic ethanol use is a global problem including among HIV-infected patients on stavudine/lamivudine/nevirapine (d4T/3TC/NVP) regimen. The study determined the effect of chronic ethanol use on the therapeutic window of d4T, 3TC and NVP in HIV-infected patients using alcohol-use biomarkers to screen patients for chronic ethanol use. Methods: A case-control study using repeated measures design with serial measurements was used to quantify drugs in plasma. The WHO alcohol use disorder identification test (AUDIT) tool was initially used to screen patients for chronic alcohol use, and then they were further sorted using alcohol-use bioamarkers (γ-glutamyl transferase ≥55.0 IU; mean corpuscular volume, ≥96 fl, aspartate amino transferase/alanine aminotransferase ratio ≥2.0 value). A total of 41 patients (26 in the alcohol group and 15 in the control group) were followed up for 9 months with blood sampling done at 3-month intervals. Plasma drug concentrations were quantified using a Shimadzu Class-VP™ HPLC data system version 6.1. Data was analyzed using SAS 2003 version 9.1 statistical package with repeated measures fixed model. Means were compared using Student's t-test. Results: The mean steady-state plasma drug concentrations of d4T and 3TC in the alcohol group were lower than that in the control group during the 9-month period of follow-up. For 3TC, there was a statistical difference in the mean steady-state plasma drug concentrations between the alcohol group and the control group (p≤0.05) in the 6- and 9-month period of follow-up. For NVP, in both groups they were within the reference ranges, although the drug plasma concentrations were higher in the alcohol group compared to the control group and were statistically significant (p<0.05) in 0, 3 and 6 months of follow-up. Conclusions: Chronic ethanol use by HIV-infected patients reduced the therapeutic steady-state plasma drug concentrations of d4T and 3TC and increased the NVP drug concentrations in the HIV-infected patients.

Pharmacodynamic and pharmacokinetic evaluation of coadministration of lacosamide and an oral contraceptive (levonorgestrel plus ethinylestradiol) in healthy female volunteers

To determine whether the antiepileptic drug lacosamide affects the pharmacokinetics or pharmacodynamics of a combined oral contraceptive (OC; ethinylestradiol 0.03mg plus levonorgestrel 0.15mg). This was an open-label trial in healthy female volunteers. Eligible women entered cycle 1 of the trial on the first day of menstruation. Cycle 1 was a medication-free, run-in phase of approximately 28days to confirm that normal ovulation occurred. Volunteers with confirmed ovulation entered the subsequent cycle and started taking OCs. After establishing ovulation suppression (defined as progesterone serum concentration <5.1nm on day 21 of the menstrual cycle) in volunteers taking the OCs in cycle 2, lacosamide 400mg/day was administered concomitantly in the subsequent cycle (cycle 3). The pharmacokinetic parameters of area under the concentration-time curve (AUC), maximum steady-state plasma drug concentration (Cmax ), and time to maximum concentration (tmax ) were measured for the OC components and lacosamide. A total of 37 volunteers completed cycle 1, and 32 completed cycle 2. In each of the 31 volunteers who completed the trial (through cycle 3), pharmacodynamic assessment showed progesterone serum concentration was <5.1nm on day 21 of cycle 2, when the OC was administered alone, and on day 21 of cycle 3, when lacosamide was administered concomitantly. The AUC of ethinylestradiol alone versus together with lacosamide was 1,067±404 versus 1,173±330pgh/ml. Corresponding values of Cmax were 116.9±48.8 versus 135.7±28.6pg/ml. For levonorgestrel, the AUC alone was 74.2±21.4 versus 80.9±18.5ngh/ml with lacosamide. Corresponding values of Cmax were 6.7±1.9 versus 7.4±1.5ng/ml. The AUC and Cmax point estimates and almost all 90% confidence intervals (except for Cmax of ethinylestradiol) for ethinylestradiol and levonorgestrel (with and without lacosamide) were within the conventional bioequivalence range, and no relevant changes in tmax were observed for ethinylestradiol (1.5±0.6h alone vs. 1.4±0.7h with lacosamide) or for levonorgestrel (1.5±1.0h alone vs. 1.1±0.6h with lacosamide). Lacosamide pharmacokinetics were consistent with those observed in previous studies of lacosamide alone, with values for AUC of 113.5±20.7μgh/ml, Cmax of 13.8±2.2μg/ml, and tmax of 1.1±0.4h. Lacosamide and an OC containing ethinylestradiol and levonorgestrel have low potential for drug-drug interaction; therefore, coadministration of the two drugs is unlikely to result in contraceptive failure or loss of seizure control.

Chronic alcohol use affects therapeutic steady state plasma drug concentrations of stavudine, lamivudine and nevirapine in HIV-infected patients during 9 months follow up period: WHO AUDIT tool application

Chronic alcohol consumption is a common problem among the HIV-infected patients on HAART. The study determined the effect of chronic alcohol use on steady state plasma drug concentrations of stavudine (d4T), lamivudine (3TC) and nevirapine (NVP) in HIV-infected patients during the 9 months follow up period. It also determined whether there were some patients with undetectable plasma drug concentrations in their plasma during the follow up. A case control using repeated measures design with serial measurements model, where plasma drug concentrations were measured at 3 month intervals was used. Chronic alcohol-use using WHO AUDIT tool was used to screen patients. A total of 41 patients (21 alcohol group and 20 control group) were followed up for 9 months with blood sampling done at 3 month intervals. The Shimadzu Class-VPTM HPLC Chromatography data system version 6.1 equipment with UV detector was used to measure the plasma drug concentrations. Data was analyzed using SAS 2003 version 9.1 statistical package with repeated measures fixed the model and means were compared using the student t-test. The mean steady state plasma concentration of both d4T and 3TC in chronic alcohol use group were lower than in the control group all throughout the 9 months period of follow-up. The mean steady state plasma drug concentrations of NVP were higher in the alcohol group at 0 and 3 months and lower in the 6 and 9 months as compared to the control group. The mean total plasma NVP concentration was higher in the chronic alcohol group as compared to the control group and the difference was statistically significant (p≤0.05). However some patients had undetectable plasma drug concentrations despite of having ≥ 95 % adherence rate. Chronic alcohol use by the HIV-infected patients lowers the steady state plasma drug concentrations of d4T, 3TC and NVP in patients.

No Pharmacokinetic Interaction Between Lacosamide and Valproic Acid in Healthy Volunteers

Two open-label, randomized, multiple-dose clinical studies evaluated the potential for pharmacokinetic interaction between the antiepileptic drugs lacosamide and valproic acid. The influence of lacosamide on valproic acid pharmacokinetics (trial A) and valproic acid on lacosamide pharmacokinetics (trial B) was investigated in 32 healthy male volunteers, 16 in each trial. Volunteers in trial A received valproic acid (300 mg bid) with randomization to either early or late addition of lacosamide (200 mg bid). Those in trial B received lacosamide (200 mg bid) with randomization to either early or late addition of valproic acid (300 mg bid). Area under the concentration-time curve during a 12-hour dosing interval at steady state (AUC(τ,ss)) and maximum steady-state plasma drug concentration (C(max,ss)) were measured for each drug alone and together and tested for equivalence. The point estimates (90% confidence intervals) for AUC(τ,ss) and C(max,ss) were 104% (99%-109%) and 101% (97%-107%), respectively, for valproic acid and 100% (98%-103%) and 101% (96%-107%), respectively, for lacosamide, which were within the generally accepted equivalence range of 80% to 125%. No changes in the rate or extent of absorption, terminal half-life, or time to maximum concentration were observed. These results suggest that lacosamide and valproic acid have no relevant pharmacokinetic drug-drug interaction.

Voriconazole pharmacokinetics and photosensitivity in children with cystic fibrosis

BackgroundA high incidence of adverse skin reactions following long-term oral administration of voriconazole in children with cystic fibrosis and allergic bronchopulmonary aspergillosis (ABPA). The aim was to study the pharmacokinetics of voriconazole in these patients and to determine a possible association between drug levels and adverse effects. MethodsMultiple venous blood samples were collected for HPLC determination of voriconazole concentrations and routine blood tests. Adverse events were recorded. ResultsNo significant correlation was found between incidence of photosensitivity and voriconazole serum levels in 6 of 8 children with ABPA. 80% of patients had trough voriconazole concentrations<1000ng/mL and were highly variable. ConclusionsLong-term voriconazole therapy and greater sun exposure in Greece appear to play a major role in the occurrence of photosensitivity. Steady-state plasma drug concentrations were found to be highly variable and below the recommended therapeutic range in most patients, without any apparent negative influence on outcome.

Bioavailability and pharmacokinetics of S-propargyl-L-cysteine, a novel cardioprotective agent, after single and multiple doses in Beagle dogs

As a novel hydrogen sulfide-modulated agent, S-propargyl-L-cysteine (SPRC) is proven to be a potent cardioprotective candidate. Bioavailability and pharmacokinetics of SPRC (20 mg/kg) in beagle dogs after oral and intravenous administrations were investigated in this study. Plasma concentrations of SPRC were measured by a LC-MS/MS method.Intravenous administration of SPRC (single dose) to beagle dogs gave a mean plasma half-life of 14.7 h, mean clearance of 0.4 ml min−1 kg−1 and mean apparent volume of distribution of 0.56 L/kg. Single oral administration was completely, fast absorbed (Tmax= 0.33 ± 0.20 h) with a mean absolute availability of 112% and mean plasma half-life of 16.5 h.Multiple oral administration (once daily for 10 consecutive days) of SPRC to dogs resulted in steady state plasma drug concentration being reached after seven doses and didn’t cause obvious accumulation. No significant difference was found between the single and multiple pharmacokinetic parameters.

Prediction of Human Oral Plasma Concentration-Time Profiles Using Preclinical Data

Empirically based methods remain one of our tools in human pharmacokinetic predictions. The Dedrick approach and the steady-state plasma drug concentration (C(ss))-mean residence time (MRT) approach are based on the assumption that concentration-time profiles are similar among species, including man, and that curves derived from a variety of animal species can be superimposed after mathematical transformation. In the Dedrick approach the transformation is based on the slope and intercept of the allometric relationship. The C(ss)-MRT approach is based on the implementation of measured animal and predicted human MRT and dose/volume of distribution at steady state (V(ss)). The aims of the present study were to compare the predictive performance of concentration-time profiles obtained by these approaches, to evaluate the prediction of individual pharmacokinetic parameters by these approaches and to further refine these approaches incorporating the experience from our previous work. A retrospective analysis using 35 proprietary compounds developed at Johnson & Johnson Pharmaceutical Research and Development was conducted to compare the accuracies of the Dedrick and C(ss)-MRT approaches for predicting oral concentration-time profiles and pharmacokinetic parameters in man. In the first step, input for the transformation was based on simple allometry. Then we assessed whether both methods could be fine-tuned by systematically incorporating correction factors (maximum life span potential, brain weight and plasma protein binding), depending on the interspecies relationship. In addition, for the C(ss)-MRT approach, we used formulas based on multivariate regression analysis as input for the transformation. Inclusion of correction factors significantly improved the profile predictability for the Dedrick and C(ss)-MRT approaches. This was mainly linked to an improved prediction of terminal elimination half-life (t(½)), MRT and the ratio between the maximum plasma concentration and the concentration at the last observed time point (C(max)/C(last)). No significant differences were observed between the Dedrick approach with correction factors, the C(ss)-MRT approach with correction factors and the C(ss)-MRT approach, based on the regression equations. Based on the dataset evaluated in this study, we demonstrated that human plasma concentration-time profiles and pharmacokinetic parameters could be predicted with the Dedrick and C(ss)-MRT approaches and that if correction factors were implemented, the predictions improved significantly. With the requirement of only a limited preclinical in vivo pharmacokinetic dataset, these empirical methods could offer potential in the early stages of drug discovery.