Modeling Developmental Changes in Caffeine Clearance Considering Differences between Pre- and Postnatal Period

Taguchi et al. reported that postmenstrual age (PMA) is a promising factor in describing and understanding the developmental change of caffeine (CAF) clearance. The aim of the present study was to quantify how developmental changes occur and to determine the effect of the length of the gestational period on CAF clearance. We performed a nonlinear mixed effect model (NONMEM) analysis and evaluated the fit of six models. A total of 115 samples were obtained from 52 patients with a mean age of 34.3 ± 18.2 d. The median values of gestational age (GA) and postnatal age (PNA) were 196 and 31 d, respectively. Serum CAF levels corrected for dose per body surface area (BSA) (C/D ratioBSA) were dependent on PMA rather than PNA, which supports the findings of a previous study. NONMEM analysis provided the following final model of oral clearance: CL/F = 0.00603∙WT∙∙0.877GA ≤ 196 L/h. This model takes into account developmental changes during prenatal and postnatal periods separately. The model successfully described the variation in clearance of CAF. Our findings suggest that the dosage of CAF in preterm infants should be determined based not only on body weight (WT) but also on both PNA and GA.

Scoliosis, diabetes mellitus and total laminectomy at the 4th lumbar vertebra are independent risk factors for post-laminectomy fracture around the isthmus

OBJECTIVE

We aimed to identify the risk factors and clinical outcomes for post-laminectomy fracture around the isthmus, which can cause back pain or radiculopathy.

METHODS

We performed a retrospective cohort study involving all patients who underwent laminectomy splitting the spinous process for lumbar spinal stenosis between 2010 and 2014. The primary outcome measure was post-laminectomy fracture around the isthmus. Clinical outcomes were evaluated based on reoperation rate. To evaluate risk factors for fracture, the following parameters were collected: (1) patient characteristics and concomitant diabetes mellitus, (2) lumbar scoliosis and sagittal alignment parameters, and (3) surgical data, such as rate of total laminectomy. Logistic regression analysis was performed to identify the independent risk factors for post-laminectomy fracture.

RESULTS

Twelve of the 92 patients suffered a post-laminectomy fracture around the isthmus. Logistic regression analysis revealed that diabetes mellitus (odds ratio [OR]: 15.41; 95% confidence interval [CI]: 2.93-80.98; P=0.001), L4 total laminectomy (OR: 14.68; 95% CI: 1.51-142.76; P=0.021), and lumbar scoliosis (OR: 5.72; 95% CI: 1.16-28.21; P=0.032) were independent risk factors. The fracture group included 2 patients (16.7%) who required reoperation at the decompression level for recurrent leg pain, whereas the non-fracture group included 2 (2.5%) who underwent reoperation at a level different from the index procedure.

CONCLUSIONS

Post-laminectomy fractures around the isthmus were significantly associated with scoliosis, diabetes mellitus, and total laminectomy at L4. Total laminectomy at L4 is best avoided to reduce the risk of post-laminectomy fracture in patients with scoliosis or diabetes mellitus.

Cardiovascular and adenylate cyclase stimulant properties of NKH477, a novel water-soluble forskolin derivative

The cardiovascular effects of NKH477 (6-(3-dimethylaminopropionyl)forskolin hydrochloride), a novel water-soluble forskolin derivative, were investigated in dogs. Intravenous (i.v.) injections of NKH477 (1-30 micrograms/kg) caused dose-related increases in left ventricular dP/dtmax (LVdP/dtmax), coronary and femoral artery blood flow (CBF, FBF), heart rate (HR), and myocardial oxygen consumption (MVO2) and a dose-related decrease in blood pressure (BP) in anesthetized dogs. The regression analysis between CBF and MVO2 showed that NKH477 did not influence substantially the balance of oxygen supply and demand. Infusions of NKH477 (0.15-0.6 microgram/kg/min i.v.) also increased LVdP/dtmax, cardiac output (CO), and HR and decreased BP, pulmonary arterial diastolic pressure, and total peripheral resistance (TPR) in a dose-dependent manner. In contrast to forskolin, NKH477 administered intraduodenally (0.05-0.2 mg/kg) and orally (0.15 and 0.3 mg/kg) clearly exhibited cardiovascular actions, as it did in i.v. administration, indicating that NKH477 is orally active. No arrhythmias were induced by NKH477 in any study. NKH477, like forskolin, showed adenylate cyclase stimulant activity in guinea pig ventricular membrane but did not inhibit Na+, K(+)-ATPase or phosphodiesterase (PDE) activity. Thus, NKH477 can be characterized as a potent, orally active, water-soluble forskolin derivative, which suggests that NKH477 is a useful inodilator for treatment of heart failure, especially in the severe stage with beta-adrenoceptor downregulation.

Mechanisms of inhibitory action of phenylephrine in guinea-pig taenia coli

The effect of phenylephrine, an alpha-agonist, on the Ca movements and the influence of removal of external Na+ on the relaxant activity of phenylephrine were examined in the taenia coli of guinea pigs. Phenylephrine (10(-7)-10(-5)M) caused dose-dependent relaxation of the taenia coli contracted by 20 mM KCl in Locke-Ringer solution. Phenylephrine (10(-5) M) suppressed the spike discharges of the taenia coli evoked by 20 mM KCl without affecting the membrane potential, and this was accompanied by the muscle relaxation. Phenylephrine also inhibited the cellular 45Ca-uptake in the taenia coli, but had no discernible effect on the 45Ca-efflux from the smooth muscle. These effects of phenylephrine were not observed in a Na-free solution or in the highly depolarized smooth muscle. These findings suggest that the inhibition of Ca-influx in the taenia coli may be involved in the phenylephrine-induced relaxation in the partly depolarized tissue. Reasons for reduction of phenylephrine action encountered under the Na-free condition were also discussed.