Comparison of the effects of nadolol and bisoprolol on the isoprenaline-evoked dilatation of the dorsal hand vein in man

A Comprehensive Physiologically Based Pharmacokinetic Model of Nadolol in Adults with Renal Disease and Pediatrics with Supraventricular Tachycardia

Nadolol is a long-acting non-selective β-adrenergic antagonist that helps treat angina and hypertension. The current study aimed to develop and validate the physiologically based pharmacokinetic model (PBPK) of nadolol in healthy adults, renal-compromised, and pediatric populations. A comprehensive PBPK model was established by utilizing a PK-Sim simulator. After establishing and validating the model in healthy adults, pathophysiological changes i.e., blood flow, hematocrit, and GFR that occur in renal failure were incorporated in the developed model, and the drug exposure was assessed through Box plots. The pediatric model was also developed and evaluated by considering the renal maturation process. The validation of the models was carried out by visual predictive checks, calculating predicted to observed (Rpre/obs) and the average fold error (AFE) of PK parameters i.e., the area under the concentration-time curve (AUC0-t), the maximum concentration in plasma (Cmax), and CL (clearance). The presented PBPK model successfully simulates the nadolol PK in healthy adults, renal-impaired, and pediatric populations, as the Rpre/obs values of all PK parameters fall within the acceptable range. The established PBPK model can be useful in nadolol dose optimization in patients with renal failure and children with supraventricular tachycardia.

Superficial venous vascular response of the resting limb during static exercise and postexercise muscle ischemia

Superficial venous vascular response to exercise is mediated sympathetically, although the mechanism is not fully understood. We examined whether sympathetic activation via muscle metaboreflex plays a role in the control of a superficial vein in the contralateral resting limb during exercise. The experimental condition involved selective stimulation of muscle metaboreceptors: 12 subjects performed static handgrip exercises at 45% maximal voluntary contraction for 1.5 min followed by a recovery period with arterial occlusion of the exercise arm (OCCL). For the control condition (CONT), the same exercise protocol was performed except that the recovery period occurred without arterial occlusion. Heart rate (HR) and mean arterial blood pressure (MAP) were measured. The cross-sectional area of the basilic superficial vein (CSAvein) and blood velocity (Vvein) in the resting upper arm were measured by ultrasound while the cuff on resting upper arm was inflated constantly to a subdiastolic pressure of 50 mm Hg. Basilic vein blood flow (BFvein) was calculated as CSAvein × Vvein. During exercise under both OCCL and CONT, HR and MAP increased (p < 0.05), while CSAvein decreased (p < 0.05). During recovery under OCCL, HR returned to baseline, but the exercise-induced increase in MAP and decrease in CSAvein were maintained (p < 0.05). During recovery under CONT, HR, MAP, and CSAvein returned to baseline. BFvein did not change during exercise or recovery under either condition. These results suggest that sympathoexcitation via muscle metaboreflex may be one of the factors responsible for exercise-induced constriction of the superficial veins per se in the resting limb.

Reproducibility of dorsal hand vein responses to phenylephrine and prostaglandin F2 alpha using the dorsal hand vein compliance method

Assessment of drug-induced venodilation by the dorsal hand vein compliance method requires stable constriction of the vein. This study was designed to investigate intra- and intersubject reproducibility of the venous preconstriction technique in response to phenylephrine and prostaglandin F2 alpha and to determine the influence of basal vein size. Twelve healthy male nonsmokers participated in a prospective cross-over study. Inter- and intrasubject variability was tested in response to phenylephrine and PGF2 alpha on different study days in the same hand vein. The dose of the respective constrictor causing approximately 80% constriction of the vein (ED80) was determined and infused for another 100 minutes. Actual vein size was measured every 5 minutes. Coefficient of variation and regression analyses were performed to analyze influence of vessel size on ED80 of the respective constrictor. Adjusted constriction levels were stable and well reproducible in all subjects. The intersubject coefficient of variation of ED80 ranged from 0.9% to 6.7% for phenylephrine and from 0.9% to 6.9% for PGF2 alpha. Whereas responses to phenylephrine were independent of basal vein diameter, there was a positive correlation between ED80 of PGF2 alpha and basal vein size. Thus, the hand vein compliance method is a suitable method to study dilatory responses in phenylephrine- or PGF2 alpha-constricted veins with considerable interindividual but small intraindividual variability. However, in such studies, phenylephrine appears to be a more reliable tool than PGF2 alpha.