Population pharmacokinetics of olanzapine in children.

AIMS: The aim of this study was to evaluate the population pharmacokinetics (PopPK) of olanzapine in children and devise a model-informed paediatric dosing scheme. METHODS: The PopPK of olanzapine was characterized using opportunistically collected plasma samples from children receiving olanzapine per standard of care for any indication. A nonlinear mixed effect modelling approach was employed for model development using the software NONMEM (v7.4). Simulations from the developed PopPK model were used to devise a paediatric dosing scheme that targeted comparable plasma exposures to adolescents and adults. RESULTS: Forty-five participants contributed 83 plasma samples towards the analysis. The median (range) postnatal age and body weight of participants were 3.8 years (0.2-19.2) and 14.1 kg (4.2-111.7), respectively. The analysis was restricted to pharmacokinetic (PK) samples collected following enteral administration (oral and feeding tube). A one-compartment model with linear elimination provided an appropriate fit to the data. The final model included the covariates body weight and postmenstrual age (PMA) on apparent olanzapine clearance (CL/F). Typical CL/F and apparent volume of distribution (scaled to 70 kg) were 16.8 L/h (21% RSE) and 663 L (13% RSE), respectively. Developed dosing schemes used weight-normalized doses for children ≤6 months postnatal age or <15 kg and fixed doses for children ≥15 kg. CONCLUSION: We developed a paediatric PopPK model for enterally-administered olanzapine. To our knowledge, this analysis is the first study to characterize the PK of olanzapine in participants ranging from infants to adolescents. Body weight and PMA were identified as influential covariates for characterizing developmental changes in olanzapine apparent clearance.

Population Pharmacokinetics of Doxycycline in Children.

Doxycycline is a tetracycline-class antimicrobial labeled by the United States (U.S.) Food and Drug Administration for children >8 years of age for many common childhood infections. Doxycycline is not labeled for children ≤8 years of age, due to the association between tetracycline class antibiotics and tooth staining, although doxycycline may be used off-label in severe conditions. Accordingly, there is a paucity of pharmacokinetic (PK) data to guide dosing in children 8 years and younger. We leveraged opportunistically-collected plasma samples after intravenous (IV) and oral doxycycline doses received per standard of care to characterize the PK of doxycycline in children of different ages, and evaluated the effect of obesity and fasting status on PK parameters.We developed a population PK model of doxycycline using data collected from 47 patients 0-18 years of age, including 14 participants ≤8 years. We developed a 1 compartment PK model and found doxycycline clearance to be 3.32 L/h/70 kg and volume to be 96.8 L/70kg for all patients; comparable to values reported in adults. We estimated a bioavailability of 89.6%, also consistent with adult data. Allometrically scaled clearance and volume of distribution did not differ between children 2 to ≤8 years of age and children >8 to ≤18 years of age, suggesting that younger children may be given the same per kg dosing. Obese and fasting status were not selected for inclusion in the final model. Additional doxycycline PK samples collected in future studies may be used to improve model performance and maximize its clinical value.

Enhancement in deposition and permeation of 5-fluorouracil through human epidermis assisted by peptide dendrimers.

Enhancing the deposition and permeation of 5-fluorouracil across human epidermis assisted by appropriately charged and well-defined peptide dendrimers was investigated. Peptide dendrimers with arginine as the terminal amino acid and having a range of terminal positive charges (4(+), 8(+) and 16(+)) were synthesized by solid phase peptide synthesis. Various parameters including effect of peptide dendrimers on the solubility and partition coefficient of 5-FU, degradation of drug in skin as well as deposition and permeation of 5-FU in/through skin were studied. All the tested dendrimers increased the aqueous solubility and partition coefficient of 5-FU with each also significantly (p < 0.05) enhancing the deposition and permeation of 5-FU in/across human epidermis in a concentration-dependent manner. Of the three peptide dendrimers examined, R8 dendrimer (bearing 8(+) charge derived from four terminal arginines and MW of ≈1000 Da) showed greatest values for flux, Q(48) (cumulative amount of drug permeated at the end of 48 h) and amount of drug retained in human skin. Furthermore, this study also scrutinized and reports on the likely mechanisms by which peptide dendrimers act as transdermal permeation enhancers.

Sonophoresis-mediated permeation and retention of peptide dendrimers across human epidermis.

PURPOSE: The objective of the present study was to assess the effect of sonophoresis on the permeation rate of peptide dendrimers through human skin. METHODS: Peptide dendrimers containing arginine and histidine as terminal amino acids and having varying positive charges (arginine group: R4, R8 and R16 dendrimers, having 4(+) , 8(+) and 16(+) charges, respectively; histidine group: H4, H8 and H16 dendrimers, having 4(+) , 8(+) and 16(+) charges, respectively) were synthesized by Fmoc solid-phase peptide synthesis. The in vitro skin permeation studies were conducted using vertical-type diffusion cells and ultrasound was applied using a probe sonicator to the donor solution. The effects of varying concentrations of dendrimer with differing pH of the donor solution on the permeation rate were studied. RESULTS: All the dendrimers exhibited significantly (P<0.05) higher permeation rates with the application of ultrasound in comparison with passive diffusion studies (without ultrasound). High concentrations of H4 and R4 dendrimers were found in the receptor media compared with other dendrimers at all the concentrations tested, indicating appreciable permeation of low-molecular-weight dendrimers across the skin, assisted by sonophoresis. The opposite was true when assessing dendrimer 'retention' in skin, where it was shown to improve upon increasing dendrimer generation/molecular weight. Negligible loss of all the dendrimers (<2%) during skin permeation studies indicates that neither skin nor ultrasound adversely affects the stability of dendrimers. CONCLUSION: The present study reveals the successful application of sonophoresis in enhancing the permeation of peptide dendrimers across human skin.

Pharmacological inhibition of inducible nitric oxide synthase attenuates the development of seizures in mice.

The present study has been designed to pharmacologically expound the significance of inducible nitric oxide synthase in the pathophysiological progression of seizures using mouse models of chemically induced kindled epilepsy and status epilepticus induced spontaneous recurrent seizures. Pentylenetetrazole (40 mg kg(-1)) (PTZ) administration every second day for a period of 15 days was used to elicit kindled seizure activity in mice. Severity of kindled seizures was assessed in terms of a composite kindled seizure severity score (KSSS). Pilocarpine (100 mg kg(-1)) was injected every 20 min until the onset of status epilepticus. A spontaneous recurrent seizure severity score (SRSSS) was recorded as a measure of quantitative assessment of the progressive development of spontaneous recurrent seizures induced after pilocarpine status epilepticus. Sub-acute PTZ administration induced the development of severe form of kindled seizures in mice. Further, pharmacological status epilepticus elicited a progressive evolution of spontaneous recurrent seizures in the animals. However, treatment of aminoguanidine, a relatively selective inhibitor of inducible nitric oxide synthase, markedly and dose dependently suppressed the development of both PTZ induced kindled seizures as well as pilocarpine induced spontaneous recurrent seizures. Therefore inducible nitric oxide synthase may be implicated in the development of seizures.