Search

Objectives: The objectives of this study were to summarize antiretroviral drug concentrations in breast milk (BM) and exposure of breast-fed infants., Methods: This was a systematic review of pharmacokinetic studies of HIV-positive women taking antiretrovirals that measured drugs in BM. The quality of pharmacokinetic and laboratory methods was assessed using pre-defined criteria. Pooled ratios and 95% CIs were calculated using the generalized inverse variance method and heterogeneity was estimated by the I(2) statistic. PubMed Central, SCOPUS and LactMed databases were searched. No date or language restrictions were applied. Searches were conducted up to 10 November 2014. Clinical relevance was estimated by comparing ingested dose with the recommended therapeutic dose for each drug., Results: Twenty-four studies were included. There was substantial variability in the clinical and laboratory methods used and in reported results. Relative to maternal plasma (MP), NRTIs accumulate in BM, with BM : MP ratios (95% CI estimates) from 0.89 to 1.21 (14 studies, 1159 paired BM and MP samples). NNRTI estimates were from 0.71 to 0.94 (17 studies, 965 paired samples) and PI estimates were from 0.17 to 0.21 (8 studies, 477 paired samples). Relative to the recommended paediatric doses, a breast-fed infant may ingest 8.4% (95% CI 1.9-15.0), 12.5% (95% CI 2.6-22.3) and 1.1% (95% CI 0-3.6) of lamivudine, nevirapine and efavirenz, respectively, via BM., Conclusions: Transfer to untreated infants appears quantitatively important for some NRTIs and NNRTIs. The pharmacokinetic methods varied widely and we propose standards for the design, analysis and reporting of future pharmacokinetic studies of drug transfer during breastfeeding., (© The Author 2015. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy.)

Objectives: Despite recent advances, antibiotic therapy of ventilator-associated pneumonia (VAP) in ICU patients is still challenging. We assessed the impact of imipenem and amikacin pharmacokinetic and pharmacodynamic parameters on microbiological outcome in these patients., Patients and Methods: Patients with Gram-negative bacilli (GNB) VAP were prospectively included. Blood samples for pharmacokinetic analysis were collected after empirical administration of a combination of imipenem three times daily and one single dose of amikacin. MICs were estimated for each GNB obtained from respiratory samples. Microbiological success was defined as a ≥10(3) cfu/mL decrease in bacterial count in quantitative cultures between baseline and the third day of treatment., Results: Thirty-nine patients [median (min-max) age = 60 years (28-84) and median SAPS2 at inclusion = 40 (19-73)] were included. Median MICs of imipenem and amikacin were 0.25 mg/L (0.094-16) and 2 mg/L (1-32), respectively. Median times over MIC and over 5× MIC for imipenem were 100% (8-100) and 74% (3-100), respectively. The median C1/MIC ratio for amikacin was 23 (1-76); 34 patients (87%) achieved a C1/MIC ≥10. Microbiological success occurred in 29 patients (74%). No imipenem pharmacodynamic parameter was significantly associated with the microbiological success. For amikacin, C1/MIC was significantly higher in the microbiological success group: 26 (1-76) versus 11 (3-26) (P = 0.004)., Conclusions: In ICU patients with VAP, classic imipenem pharmacodynamic targets are easily reached with usual dosing regimens. In this context, for amikacin, a higher C1/MIC ratio than previously described might be necessary., (© The Author 2015. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

Background: The determination of dosing regimens for the treatment of malaria is largely empirical and thus a better understanding of the pharmacokinetic/pharmacodynamic properties of antimalarial agents is required to assess the adequacy of current treatment regimens and identify sources of suboptimal dosing that could select for drug-resistant parasites. Mefloquine is a widely used antimalarial, commonly given in combination with artesunate., Patients and Methods: Mefloquine pharmacokinetics was assessed in 24 healthy adults and 43 patients with Plasmodium falciparum malaria administered mefloquine in combination with artesunate. Population pharmacokinetic modelling was conducted using NONMEM., Results: A two-compartment model with a single transit compartment and first-order elimination from the central compartment most adequately described mefloquine concentration-time data. The model incorporated population parameter variability for clearance (CL/F), central volume of distribution (VC/F) and absorption rate constant (KA) and identified, in addition to body weight, malaria infection as a covariate for VC/F (but not CL/F). Monte Carlo simulations predict that falciparum malaria infection is associated with a shorter elimination half-life (407 versus 566 h) and T>MIC (766 versus 893 h)., Conclusions: This is the first known population pharmacokinetic study to show falciparum malaria to influence mefloquine disposition. Protein binding, anaemia and other factors may contribute to differences between healthy individuals and patients. As VC/F is related to the earlier portion of the concentration-time profiles, which occurs during acute malaria, and CL/F is more related to the terminal phase during convalescence after treatment, this may explain why malaria was found to be a covariate for VC/F but not CL/F., (© The Author 2014. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

Objectives: To develop a population model to describe the pharmacokinetics (PK) of intravenous meropenem in adult patients with severe burns and investigate potential relationships between dosage regimens and antimicrobial efficacy., Patients and Methods: A dose of 1 g every 8 h was administered to adult patients with total body surface area burns of ≥15%. Doses for subsequent courses were determined using results from the initial course and the patient's clinical condition. Five plasma meropenem concentrations were typically measured over the dosage interval on one to four occasions. An open, two-compartment PK model was fitted to the meropenem concentrations using NONMEM and the effect of covariates on meropenem PK was investigated. Monte Carlo simulations investigated dosage regimens to achieve a target T>MIC for ≥40%, ≥60% or ≥80% of the dose interval., Results: Data comprised 113 meropenem concentration measurements from 20 dosage intervals in 12 patients. The parameters were CL (L/h) = 0.196 L/h/kg × [1 - 0.023 × (age - 46)] × [1 - 0.049 × (albumin - 15)], V1 = 0.273 L/kg × [1 - 0.049 × (albumin - 15)], Q = 0.199 L/h/kg and V2 = 0.309 L/kg × [1 - 0.049 × (albumin - 15)]. For a target of ≥80% T>MIC, the breakpoint was 8 mg/L for doses of 1 g every 4 h and 2 g every 8 h given over 3 h, but only 4 mg/L if given over 5 min., Conclusions: Although 1 g 8 hourly should be effective against Escherichia coli and CoNS, higher doses, ideally with a longer infusion time, would be more appropriate for empirical therapy, mixed infections and bacteria with MIC values ≥4 mg/L., (© The Author 2014. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

Objectives: Previous studies of raltegravir and rifampicin have not studied the interaction when rifampicin is dosed intermittently. This study aimed to assess the pharmacokinetics of twice daily raltegravir and intermittently dosed rifampicin., Methods: This was a prospective, open, single-arm, three-part, controlled study in healthy volunteers. Over a period of 38 days subjects received 5 days of standard-dose raltegravir (400 mg twice daily) followed by 28 days of standard-dose raltegravir plus rifampicin three times a week followed by 5 days of high-dose (800 mg twice daily) raltegravir plus rifampicin three times a week. Pharmacokinetic sampling was performed on days 5, 33 and 38. Raltegravir pharmacokinetic parameters were determined by non-compartmental analysis and reported as geometric means and 90% CIs. ClinicalTrials.gov: NCT01424826., Results: Sixteen subjects (12 females) completed the study. Raltegravir trough plasma concentration (C12) was significantly lower in the presence of rifampicin when dosed at 400 mg twice daily (40%), which was not observed with 800 mg twice daily dosing. Raltegravir Cmax and AUC0-12 were both significantly higher in the presence of rifampicin when dosed at 800 mg twice daily (76% and 84%, respectively), but this dose was well tolerated., Conclusions: This study suggests that rifampicin induction of raltegravir is comparable between daily and intermittent rifampicin. In the absence of definitive clinical efficacy data to suggest otherwise, doses of 800 mg of raltegravir twice daily with rifampicin thrice weekly are well tolerated and yield higher AUCs and comparable C12 when compared with raltegravir alone., (© The Author 2014. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

Background: Current guidelines for dosing of anti-TB drugs in children advocate higher doses for rifampicin and isoniazid despite limited availability of paediatric data on the pharmacokinetics of these drugs, especially from Africa, where the burden of childhood disease remains high., Methods: Thirty children aged 6 months to 15 years underwent intensive pharmacokinetic sampling for first-line anti-TB drugs at Queen Elizabeth Central Hospital, Blantyre, Malawi. Rifampicin, isoniazid, pyrazinamide and ethambutol were dosed at 10, 5, 25 and 20 mg/kg, respectively. Plasma drug concentrations were determined using sensitive, validated bioanalytical methods and summary pharmacokinetic parameters were estimated using non-compartmental analysis., Results: The median (IQR) Cmax was 2.90 (2.08-3.43), 3.37 (2.55-4.59), 34.60 (32.30-40.90) and 1.20 (0.85-1.68) mg/L while the median (IQR) AUC0-∞ was 16.92 (11.10-22.74), 11.48 (7.35-18.93), 333.50 (279.50-487.2) and 8.65 (5.96-11.47) mg·h/L for rifampicin, isoniazid, pyrazinamide and ethambutol, respectively. For all drugs, pharmacokinetic parameters relating to drug absorption and exposure were lower than those published for adults, though similar to existing paediatric data from sub-Saharan Africa. Weight and/or dose predicted at least one measure of exposure for all drugs. Age-related decreases in CL/F for rifampicin and pyrazinamide and a biphasic elimination pattern of isoniazid were observed. Predicted AUC0 -∞ for rifampicin dosed at 15 mg/kg was comparable to that of adults while the dose required to achieve ethambutol exposure similar to that in adults was 55 mg/kg or higher., Conclusions: These data support recently revised WHO recommendations for dosing of anti-TB drugs in children, but dosing of ethambutol in children also appears inadequate by comparison with adult pharmacokinetic data., (© The Author 2015. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy.)

Objectives: Boceprevir is a first-generation direct-acting antiviral licensed for the treatment of hepatitis C infection. Sildenafil is an oral therapy for erectile dysfunction. As boceprevir is a potent inhibitor of CYP3A4, potential pharmacokinetic interactions may occur when it is coadministered with sildenafil. The aim of this study was to assess the pharmacokinetic profile of sildenafil and boceprevir when dosed separately and together in healthy volunteers., Methods: Thirteen male subjects completed the following study procedures: phase 1 (Day 0), a single dose of 25 mg of sildenafil was administered; washout period (Days 1-9); phase 2 (Days 10-15), 800 mg of boceprevir three times a day was administered; and phase 3 (Day 16), 800 mg of boceprevir and 25 mg of sildenafil were administered. All drugs were administered in the fed state. Intensive pharmacokinetic sampling was undertaken on Days 0, 15 and 16. Differences in the pharmacokinetic parameters of sildenafil, N-desmethyl-sildenafil and boceprevir between phase 3 and the earlier phases were evaluated by changes in the geometric mean ratios (GMRs)., Results: All the drugs were well tolerated with no safety concerns arising. In the presence of boceprevir (phase 3 versus phase 1), the GMR for the plasma Cmax and the AUC24 for sildenafil increased by 1.9-fold (95% CI 1.5-2.4) and 2.7-fold (95% CI 2.1-3.4), respectively, whereas a reduction in the Cmax of N-desmethyl-sildenafil was observed (GMR 0.5, 95% CI 0.4-0.7). No significant changes in boceprevir exposure were observed between phases 3 and 2., Conclusions: Exposure of sildenafil is increased in the presence of boceprevir. A dose adjustment of sildenafil is therefore necessary. An initial dose of 25 mg of sildenafil is suggested., (© The Author 2015. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

Objectives: Caspofungin is used for treatment of invasive fungal infections. As the pharmacokinetics (PK) of antimicrobial agents in critically ill patients can be highly variable, we set out to explore caspofungin PK in ICU patients., Methods: ICU patients receiving caspofungin were eligible. Patients received a loading dose of 70 mg followed by 50 mg daily (70 mg if body weight >80 kg); they were evaluable upon completion of the first PK curve at day 3. Additionally, daily trough samples were taken and a second PK curve was recorded at day 7. PK analysis was performed using a standard two-stage approach., Results: Twenty-one patients were evaluable. Median (range) age and body weight were 71 (45-80) years and 75 (50-99) kg. PK sampling on day 3 (n = 21) resulted in the following median (IQR) parameters: AUC0-24 88.7 (72.2-97.5) mg·h/L; Cmin 2.15 (1.40-2.48) mg/L; Cmax 7.51 (6.05-8.17) mg/L; V 7.72 (6.12-9.01) L; and CL 0.57 (0.54-0.77) L/h. PK sampling on day 7 (n = 13) resulted in AUC0-24 107.2 (90.4-125.3) mg·h/L, Cmin 2.55 (1.82-3.08) mg/L, Cmax 8.65 (7.16-9.34) mg/L, V 7.03 (5.51-7.73) L and CL 0.54 (0.44-0.60) L/h. We did not identify any covariates significantly affecting caspofungin PK in ICU patients (e.g. body weight, albumin, liver function). Caspofungin was well tolerated and no unexpected side effects were observed., Conclusions: Caspofungin PK in ICU patients showed limited intraindividual and moderate interindividual variability, and caspofungin was well tolerated. A standard two-stage approach did not reveal significant covariates. Our study showed similar caspofungin PK parameters in ICU patients compared with non-critically ill patients., (© The Author 2014. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

Objectives: Mefloquine/artesunate has recently been developed as a fixed-dose combination, providing a promising rescue/alternative treatment for malaria during pregnancy. However, limited data are available on the effect of pregnancy on its pharmacokinetic properties. This study was conducted to assess the pharmacokinetic properties of mefloquine/carboxymefloquine and artesunate/dihydroartemisinin in pregnant and non-pregnant women with uncomplicated malaria., Methods: Twenty-four women in their second and third trimesters of pregnancy and 24 paired non-pregnant women were enrolled. All patients were treated for uncomplicated Plasmodium falciparum malaria with a standard fixed-dose combination of oral mefloquine and artesunate one daily over 3 days. Frequent blood samples were collected before treatment and at scheduled times post-dose for the drug measurements and pharmacokinetic analyses. The study was registered at www.clinicaltrials.gov (identifier: NCT00701961)., Results: The total median exposure to mefloquine and dihydroartemisinin was not significantly different between the pregnant and non-pregnant women (P>0.05). There was a trend of higher exposure to mefloquine in the pregnant women, but this difference did not reach statistical significance (656700 versus 542400 h × ng/mL; P=0.059). However, the total exposure to carboxymefloquine was 49% lower during pregnancy (735600 versus 1499000 h × ng/mL; P<0.001) and the total drug exposure to artesunate was 42% higher during pregnancy (89.0 versus 62.9 h × ng/mL; P=0.039) compared with non-pregnant controls., Conclusions: The plasma levels of mefloquine and dihydroartemisinin appeared to be similar in both pregnant and non-pregnant women, but there were significant differences in carboxymefloquine and artesunate exposure. The data presented here do not warrant a dose adjustment in pregnant patients, but an extensive analysis of the data could provide a better understanding of these findings., (© The Author 2014. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

Objectives: To evaluate the pharmacokinetics of piperacillin/tazobactam in critically ill patients undergoing continuous renal replacement therapy (CRRT) and to assess the success of the therapy against susceptible bacteria., Patients and Methods: Sixteen patients undergoing CRRT with different degrees of renal function were included in the study. Blood and ultrafiltrate samples were drawn after administration of piperacillin/tazobactam (4/0.5 g) every 4, 6 or 8 h. The data were analysed by a population approach using NONMEM 7.2. The probability of target attainment (PTA) of maintaining free piperacillin levels above the MIC during the entire dosing interval was estimated by simulation of intermittent and continuous infusions., Results: The pharmacokinetics of piperacillin and tazobactam were best described by two-compartment models where the elimination of both drugs was conditioned by renal [dependent on creatinine clearance (CLCR)], non-renal and extracorporeal clearances. A 20 min infusion of piperacillin/tazobactam administered every 6 h provided high PTAs against MICs ≤ 32 mg/L in patients with severe renal failure. In patients with normal or moderate renal function PTAs ≥ 90% were only obtained up to MICs ≤ 8 mg/L with short infusions. However, simulating continuous infusion, higher probabilities of success were obtained against MICs of 32 and 16 mg/L when CLCR was 50 and 100 mL/min, respectively., Conclusions: Population pharmacokinetic models have been developed and validated for piperacillin and tazobactam. Based on the pharmacokinetic/pharmacodynamic analysis, dosing recommendations are given considering the residual renal function of the patient and the MIC for the isolated bacteria.

Objectives: To confirm whether 7 days of phenytoin, an enzyme inducer, would decrease the elimination half-life of single-dose nevirapine and to investigate its effect on the development of nevirapine resistance in pregnant, HIV-infected women., Methods: In a pharmacokinetic pilot trial (NCT01187719), HIV-infected, antiretroviral (ARV)-naive pregnant women ≥18 years old from Zambia and Tanzania and with CD4 cell counts >350 cells/mm(3) were randomized 1 : 1 to a control (zidovudine pre-delivery, single-dose nevirapine/zidovudine/lamivudine at delivery and zidovudine/lamivudine for 7 days post-delivery) or an intervention (control plus 184 mg of phenytoin once daily for 7 days post-delivery) group. Primary endpoints were the pharmacokinetics of and resistance to nevirapine., Results: Thirty-five and 37 women were allocated to the control and intervention groups, with median (IQR) ages of 27 (23-31) and 27 (23-33) years, respectively. Twenty-three and 23 women had detectable nevirapine levels at delivery and subsequent samples in the control and the intervention groups, respectively. Geometric mean (GM) (95% CI) plasma levels of nevirapine at delivery were 1.02 (0.58-1.78) mg/L and 1.14 (0.70-1.86) mg/L in the control and intervention groups, respectively (P = 0.76). One week after delivery, 0/23 (0%) and 15/22 (68%) control and intervention mothers, respectively, had undetectable levels of nevirapine (<0.05 mg/L; P<0.001). One week later, the figures were 10/21 (48%) and 18/19 (95%) mothers, respectively (P = 0.002). The GM (95% CI) half-life of nevirapine was 63.2 (52.8-75.7) versus 25.5 (21.6-30.1) h in the control group versus the intervention group (P < 0.001). New nevirapine mutations were found in 0/20 (0%) intervention-group mothers versus 1/21 (5%) control-group mothers. Overall, there was no difference in adverse events reported between the control and intervention arms (P > 0.28)., Conclusions: Adding 7 days of an enzyme inducer to single-dose nevirapine to prevent mother-to-child transmission of HIV significantly reduced subtherapeutic nevirapine levels by shortening the half-life of nevirapine. As prolonged subtherapeutic nevirapine dosage leads to the emergence of resistance, single-dose nevirapine could be used with phenytoin as an alternative if other ARVs were unavailable.