Entire Treatment Duration Research Articles

Kinetics and intrapulmonary disposition of tilmicosin after single and repeated oral bolus administrations to rabbits

Tilmicosin (TIM, Pulmotil) was administered to eight rabbits by oral gavage at a dose of 12.5 mg/kg body weight for 2, 5, and 7 days, and its plasma kinetics and intrapulmonary disposition were investigated. TIM concentrations in plasma samples collected after days 1 and 6 of treatment were measured by high-performance liquid chromatography with ultraviolet detection. The pharmacokinetic parameters, obtained by non-compartmental analysis of TIM plasma concentrations, did not show any significant variations between days 1 and 6. From the second day of treatment, TIM concentrations attained in lung tissue and pulmonary alveolar macrophages (PAM) exceeded those in plasma by 7- and 400-fold, respectively, and high levels were maintained in lung tissues during the entire treatment duration. After the first day of withdrawal, a fast decline in TIM levels in both plasma and lung tissue was observed, but in PAM, much higher concentrations were maintained after 3 days of TIM withdrawal.

Topiramate concentrations in neonates treated with prolonged whole body hypothermia for hypoxic ischemic encephalopathy

Therapeutic hypothermia reduces mortality and neurologic impairment in neonates with hypoxic-ischemic encephalopathy. Topiramate exerts a neuroprotective effect in asphyxiated neonatal animal models. However, no studies have investigated the association of hypothermia and topiramate, because topiramate pharmacokinetics during hypothermia and the optimal administration schedule are unknown. The influence of hypothermia on topiramate pharmacokinetics was evaluated in asphyxiated neonates treated with prolonged whole-body hypothermia and topiramate. Thirteen term newborns were treated with mild or deep whole body hypothermia for 72 h; all received oral topiramate, 5 mg/kg once a day for the first 3 days of life, and seven had concomitant phenobarbital treatment. Topiramate concentrations were measured on serial dried blood spots. Topiramate concentrations were within the reference range in 11 of 13 newborns, whereas concentrations exceeded the upper limit in 2 of 13, both newborns on deep hypothermia. Topiramate concentrations reached a virtual steady state in nine newborns, for whom pharmacokinetic parameters were calculated. Values of topiramate maximal and minimal concentration, half-life, average concentration, and area under the time-concentration curve resulted in considerably higher values than those reported in normothermic infants. With respect to normothermic infants, time of maximal concentration was mildly delayed and apparent total body clearance was lower, suggesting slower absorption and elimination. Pharmacokinetic parameters did not differ significantly between infants on deep versus mild hypothermia and in those on topiramate monotherapy versus add-on phenobarbital. Most neonates on prolonged hypothermia treated with topiramate 5 mg/kg once a day exhibited drug concentrations within the reference range for the entire treatment duration.

The impact of duration of antibiotic exposure on bacterial resistance predictions using in vitro dynamic models

To explore whether the duration of in vitro simulated antibiotic exposure influences bacterial resistance, time-dependent amplification of resistant subpopulations of Staphylococcus aureus was studied in 10 day simulations in a dynamic model with daptomycin as a prototypic agent. S. aureus ATCC 43300 was exposed to once-daily dosing of daptomycin at subtherapeutic ratios of 24 h area under the curve (AUC(24)) to the MIC (32 and 64 h). To provide an integral presentation of the time course of mutants grown on agar plates containing 2x and 4x the MIC of daptomycin, areas under the bacterial mutant kinetic curves (AUBC(M)s) were calculated. Daptomycin-resistant S. aureus mutants were enriched gradually over the entire treatment duration, with systematic increases in AUBC(M) and concomitant decreases in susceptibility. AUBC(M) analyses were also applied to resistance data reported from other studies with S. aureus exposed to daptomycin and garenoxacin over a wide range of AUC(24)/MIC ratios. Although the maximal AUBC(M)s were greater with longer than with shorter exposures, the treatment or observation durations did not influence the predicted anti-mutant AUC(24)/MIC ratios. These findings suggest that the duration of in vitro simulated antibiotic exposure is important for estimates of the maximal enrichment of resistant mutants but not for the prediction of the anti-mutant AUC(24)/MIC ratio.

Obstructive sleep apnoea is improved by a prolonged treatment of gastrooesophageal reflux with omeprazole

Background Obstructive sleep apnoea has been demonstrated to induce gastrooesophageal reflux through highly negative intrathoracic pressure during the attacks. However, we believe that gastrooesophageal reflux on its part may favour or aggravate the apnoea attacks. Aims We investigated whether the treatment of gastrooesophageal reflux with omeprazole is able to decrease apnoea attacks. Patients and methods Twenty patients (mean age 55.4 years, range 49–73 years; 17 males) with confirmed obstructive sleep apnoea at overnight polysomnography and pathological gastrooesophageal reflux at ambulatory 24-h oesophageal pHmetry were asked to note in a diary the occurrence of apnoea attacks for a basal period of 4 weeks. Subsequently, the patients were randomly and in a double-blind manner treated with omeprazole 20 mg (10 patients, group A) or placebo (10 patients, group B) by giving 1 cp 30 min before breakfast and 1 cp 30 min before dinner for another 6 weeks with a diary documentation. The results were averaged weekly and over the entire treatment duration and a statistical comparison was made between the groups and within each group before and after treatment. Results The mean weekly frequency of apnoea attacks of group A during the entire period of treatment with omeprazole was significantly decreased with respect to the basal period and was significantly lower than that of group B. The weekly frequency of apnoea attacks in group A started to be significantly lower from the third week than the corresponding values of both group B and the basal period, reaching a decrease of about 73% in the sixth week. Conclusion The occurrence of apnoea attacks progressively decreased during the treatment of gastrooesophageal reflux with omeprazole. This fact suggests that gastrooesophageal reflux may play a role in triggering and/or worsening obstructive sleep apnoea.

Effects of Anabolic Androgenic Steroid Use on Cardiovascular Status and Reproduction in Adult Male Athletes

Anabolic androgenic steroid (AAS) abuse by man represents a significant health risk due to the potential long-term negative physical sequele. The present work aims to detect the effects of chronic (AAS) use in adult males and their consequences on cardiovascular and gonadal status. This study was divided into two parts: The human part was carried on eighteen strength athletes self- administered several steroids (oral and intramuscular) simultaneously for about 14 weeks. Serum lipids and lipoproteins were assessed during use and 6 weeks after drug cessation, as indicators of the risk for cardiovascular disease. Plasma sex hormones as testosterone (T), luteinizing hormone (LH) and follicle stimulating hormone (FSH) were also determined to clarify the effect of AAS on the testicular endocrine function. The experimental part was carried on 40 rats. They were divided into two groups: Control and an AAS-treated group. Each rat in AAS group administered 5 mg/kg body wt testosterone propionate (TP) intramuscularly twice weekly for 8 weeks. At the end, plasma sex hormones, intra-testicular T levels were assessed and testes of the sacrificed animals were examined histologically as well. The results of the human part showed significant increase in LDL level and significant fall in HDL. These changes were paralleled by significant increase in Apo lipoproteins-B concentration and decrease in both Apo-Al& Lp(a) concentration. On the other hand, sex hormones were significantly suppressed. Six weeks after AAS withdrawal, lipoprotein variables had not returned to baseline concentrations. As regard the experimental part; testes weight and testicular sperm numbers were markedly decreased compared with the control. Testicular tissue examination revealed arrest of advanced spermatogenesis in the seminiferous tubules and a severe depletion of the number of Leydig cells. Plasma levels of FSH and LH were decreased. Plasma T levels remained at the normal range throughout the entire treatment duration. Intra-testicular T levels were significantly reduced. It was concluded that administration of AAS produces comparable profound unfavorable effects on lipids.

Evaluation of intrafraction patient movement for CNS and head & neck IMRT.

Intrafraction patient motion is much more likely in intensity-modulated radiation therapy (IMRT) than in conventional radiotherapy primarily due to longer beam delivery times in IMRT treatment. In this study, we evaluated the uncertainty of intrafraction patient displacement in CNS and head and neck IMRT patients. Immobilization is performed in three steps: (1) the patient is immobilized with thermoplastic facemask, (2) the patient displacement is monitored using a commercial stereotactic infrared IR camera (ExacTrac, BrainLab) during treatment, and (3) repositioning is carried out as needed. The displacement data were recorded during beam-on time for the entire treatment duration for 5 patients using the camera system. We used the concept of cumulative time versus patient position uncertainty, referred to as an uncertainty time histogram (UTH), to analyze the data. UTH is a plot of the accumulated time during which a patient stays within the corresponding movement uncertainty. The University of Florida immobilization procedure showed an effective immobilization capability for CNS and head and neck IMRT patients by keeping the patient displacement less than 1.5 mm for 95% of treatment time (1.43 mm for 1, and 1.02 mm for 1, and less than 1.0 mm for 3 patients). The maximum displacement was 2.0 mm.

Abnormal bone architecture and biomechanical properties with near-lifetime treatment of rats with PTH.

Skeletal effects are described for near-lifetime treatment of young, female rats with recombinant human PTH (1-34) (PTH). Rats (5-8 wk of age) were administered 0, 5, 30, or 75 microg/kg x d sc PTH for up to 2 yr, as part of an oncogenicity evaluation, which is required by regulatory agencies for potential chronic therapies. Proliferative lesions were observed in the skeleton as described in Vahle et al. (1 ); in this paper, we describe the quantitative bone data for this study. In the appendicular skeleton, PTH stimulated trabecular and endocortical mineral apposition to the near exclusion of marrow spaces at 5 microg/kg, with some periosteal apposition at 30 microg/kg, followed by considerable periosteal apposition and altered geometry at 75 microg/kg. Increased bone mass was observed for all treatment groups that substantially exceeded normal levels attained by vehicle controls and exceeded skeletal efficacy reported previously for similar doses in shorter-term studies. Dose-dependent increases in osteocalcin levels and a linear increase in wet weight of femora were observed for the entire treatment duration, suggesting nearly continuous PTH stimulation of osteoblasts and skeletal growth throughout life. Histology showed many osteocytes and prominent osteoblasts, but a conspicuous absence of osteoclasts. Morphometry showed a lack of distinction between trabecular and cortical bone. Biomechanics of vehicle controls showed that optimal mechanical integrity for the normal skeleton is observed at about 11 months of age. PTH greatly strengthened and stiffened vertebra and femora; however, the midshaft showed reduced toughness and increased brittleness with treatment, which was not the case for vertebra. Related studies of 6 and 9 months duration showed that the optimal duration for PTH skeletal efficacy was about 6 months in rats, based on toughness, strength, ultimate displacement, and architecture, especially for cortical bone. Therefore, treatment duration is an under appreciated aspect of PTH pharmacology; and PTH skeletal effects are a complex function of dose and duration. Comparative analyses showed that short-term treatment (6 months or less) is more advantageous than near-lifetime treatment, because PTH stimulates skeletal growth throughout life, resulting in abnormal architecture and untoward biomechanical properties in rats.