Receptor occupancy in lumbar CSF as a measure of the antagonist activity of atenolol, metoprolol and propranolol in the CNS

The Safety and Effectiveness of High-Dose Propranolol as a Treatment for Challenging Behaviors in Individuals With Autism Spectrum Disorders

PURPOSE/BACKGROUND

Individuals with autism spectrum disorders present with social communication deficits and a rigid adherence to sameness. Along with these symptoms, many individuals also present with severe challenging behaviors that place themselves as well as their families and communities at risk for injury. For these individuals, new and effective treatments are acutely needed. Propranolol has been used worldwide for over 50 years. Its primary indication is for hypertension, but there is evidence that, at higher doses, propranolol inhibits rage and anger through its effects on the central nervous system. This effect has been demonstrated in a variety of neuropsychiatric disorders.

METHODS/PROCEDURES

Here, we present 46 retrospective analyses of clinical cases that were followed by a psychiatrist. Propranolol was prescribed as an add-on to the patients' existing medications. The doses ranged from 120 to 960 mg per day (mean = 462 mg).

FINDINGS/RESULTS

Thirty-nine (85%) of 46 patients were found to be much improved or very much improved on the physician-rated Clinical Global Impression Improvement scale. There were few side effects noted, with only 2 subjects unable to tolerate the propranolol.

IMPLICATIONS/CONCLUSIONS

It appears that high-dose propranolol can be given safely with minimal adverse cardiovascular problems, provided that close clinical monitoring is maintained. A more rigorous clinical trial is needed to elucidate and verify its clinical utility, clinical practice parameters, and the effects of propranolol as a monotherapy versus as an add-on to the patient's existing medication regimen.

Response of nasal airway and heart rate variability to controlled nasal breathing

To investigate the responses of nasal airway and autonomic nervous system (ANS) under controlled nasal breathings. Ten healthy volunteers, aged between 21 and 37 years, were enrolled. The participants breathed either through bilateral nostrils (BNB) or unilaterally through the left nostril (UNB) at 0.25 Hz for 5 min. The electrocardiography was simultaneously recorded and the ANS activities were evaluated using heart rate variability analysis. Nasal airway resistance and related factors were measured by rhinomanometry. The results showed that the mean heartbeat interval during UNB was significantly greater than during BNB. The sympathetic modulation decreased significantly during UNB. The correlations between nasal airway resistance and mean heartbeat interval were significant for both UNB and BNB. The increase of heartbeat intervals during UNB was associated with the decrease of cardiac sympathetic activities. The changes of ANS activities and nasal airway resistance during UNB are similar to the changes caused by a prolonged lying.

A double blind, randomized trial on augmentation of labour with a combination of intravenous propranolol and oxytocin versus oxytocin only

OBJECTIVE

To compare the combination of intravenous propranolol and oxytocin with oxytocin only in augmentation of labour.

STUDY DESIGN

A prospective randomized double-blind study in an obstetric department of a large university hospital in Finland. A total of 107 parturients with arrested first stage of labour owing to inadequate uterine contractility were randomized to receive intravenously once or twice a 2 mg dose of propranolol or placebo combined with oxytocin infusion. The main outcome measure was the effect of intravenous propranolol on the frequency of Caesarean section among parturients with arrested labour. The secondary outcome measures were the duration of labour, the required dosage of oxytocin, CTG readings, neonatal outcome and maternal and cord plasma levels of beta-adrenoceptor-binding component of propranolol. Categorial variables between the groups were compared using Chi square and Fisher's exact tests. Continuous variables were compared using the Mann-Whitney U-test and Student's t-test.

RESULTS

No reduction in Caesarean section rate was found in the propranolol group. Seventy-three percent of the parturients in the propranolol group and 85% in the placebo group had spontaneous vaginal delivery, RR=0.86 (95% CI 0.70-1.05). The percentage proportion of the augmented part of labour was significantly shorter in the propranolol group than in the placebo group. No differences in the required oxytocin dosage or CTG pathology were found between the groups. Propranolol was found to be safe for the neonates. The concentrations of its beta-adrenoceptor-binding component after a 2mg intravenous dose were quite similar in parturients and neonates at the time of delivery. The active drug component crossed placental barriers with an average neonate umbilical artery/parturient venous plasma ratio of 0.7. After a 4 mg dose the active drug concentrations in parturients were rather similar to those measured after 2 mg dose, whereas in neonates there were signs of drug accumulation. No picture could be obtained from the kinetics of the beta-adrenoceptor-binding component of propranolol from the data.

CONCLUSIONS

Propranolol (2 or 4 mg i.v.) combined with oxytocin, as treatment for arrested labour did not affect the Caesarean section rate compared with placebo plus oxytocin. The percentage proportion of the augmented part of labour was significantly shorter after propranolol. Propranolol was safe for the neonates and can be used as an additional medication among parturients with arrested labour.

Sympathetic restraint of respiratory sinus arrhythmia: implications for vagal-cardiac tone assessment in humans

Clinicians and experimentalists routinely estimate vagal-cardiac nerve traffic from respiratory sinus arrhythmia. However, evidence suggests that sympathetic mechanisms may also modulate respiratory sinus arrhythmia. Our study examined modulation of respiratory sinus arrhythmia by sympathetic outflow. We measured R-R interval spectral power in 10 volunteers that breathed sequentially at 13 frequencies, from 15 to 3 breaths/min, before and after beta-adrenergic blockade. We fitted changes of respiratory frequency R-R interval spectral power with a damped oscillator model: frequency-dependent oscillations with a resonant frequency, generated by driving forces and modified by damping influences. beta-Adrenergic blockade enhanced respiratory sinus arrhythmia at all frequencies (at some, fourfold). The damped oscillator model fit experimental data well (39 of 40 ramps; r = 0.86 +/- 0.02). beta-Adrenergic blockade increased respiratory sinus arrhythmia by amplifying respiration-related driving forces (P < 0.05), without altering resonant frequency or damping influences. Both spectral power data and the damped oscillator model indicate that cardiac sympathetic outflow markedly reduces heart period oscillations at all frequencies. This challenges the notion that respiratory sinus arrhythmia is mediated simply by vagal-cardiac nerve activity. These results have important implications for clinical and experimental estimation of human vagal cardiac tone.

Mechanisms underlying very-low-frequency RR-interval oscillations in humans

BACKGROUND

Survival of post-myocardial infarction patients is related inversely to their levels of very-low-frequency (0.003 to 0.03 Hz) RR-interval variability. The physiological basis for such oscillations is unclear. In our study, we used blocking drugs to evaluate potential contributions of sympathetic and vagal mechanisms and the renin-angiotensin-aldosterone system to very-low-frequency RR-interval variability in 10 young healthy subjects.

METHODS AND RESULTS

We recorded RR intervals and arterial pressures during three separate sessions, with the patient in supine and 40 degree upright tilt positions, during 20-minute frequency (0.25 Hz) and tidal volume-controlled breathing after intravenous injections: saline (control), atenolol (0.2 mg/kg, beta-adrenergic blockade), atropine sulfate (0.04 mg/kg, parasympathetic blockade), atenolol and atropine (complete autonomic blockade), and enalaprilat (0.02 mg/kg, ACE blockade). We integrated fast Fourier transform RR-interval spectral power at very low (0.003 to 0.03 Hz), low (0.05 to 0. 15 Hz), and respiratory (0.2 to 0.3 Hz) frequencies. Beta-adrenergic blockade had no significant effect on very-low- or low-frequency RR-interval power but increased respiratory frequency power 2-fold. ACE blockade had no significant effect on low or respiratory frequency RR-interval power but modestly (approximately 21%) increased very-low-frequency power in the supine (but not upright tilt) position (P<0.05). The most profound effects were exerted by parasympathetic blockade: Atropine, given alone or with atenolol, abolished nearly all RR-interval variability and decreased very-low-frequency variability by 92%.

CONCLUSIONS

Although very-low-frequency heart period rhythms are influenced by the renin-angiotensin-aldosterone system, as low and respiratory frequency RR-interval rhythms, they depend primarily on the presence of parasympathetic outflow. Therefore the prognostic value of very-low-frequency heart period oscillations may derive from the fundamental importance of parasympathetic mechanisms in cardiovascular health.

Receptor binding assays in analysing the bioavailability and pharmacodynamic bioequivalence of active drug moieties. A study of metoprolol

The bioavailability and pharmacodynamic bioequivalence of a conventional and an experimental sustained-release formulation of 100 mg metoprolol tartrate were studied in a randomised cross-over study in seven healthy volunteers by assessing over 24 h the plasma kinetics of R,S-metoprolol, its beta 1-adrenoceptor binding component, and by determining the extent to which the active drug moiety in plasma occupied rabbit lung beta 1- and rat reticulocyte beta 2-adrenoceptors. The formulations differed markedly in their kinetic characteristics: the peak plasma concentration (Cmax) of R,S-metoprolol after administration of the conventional formulation was 140 ng.ml-1, (n = 7) and it was approximately one-third of that after the sustained-release formulation, 49 ng.ml-1, (n = 6); the AUC0-24 h-values for the formulations were 700 and 310 ng.h.ml-1, respectively. The Cmax for the beta 1-adrenoceptor binding component of metoprolol was 180 ng.ml-1 (n = 7) after administration of the conventional, and 74 ng.ml-1 after administration of the sustained-release formulation. The corresponding AUC0-24 h-values for the receptor binding component were 920 and 470 ng.h.ml-1 (n = 7). Thus, the kinetic differences between R,S-metoprolol and the beta 1-receptor binding component were considerable and they were affected by the type of formulation. In general, after administration of the sustained-release formulation, the percentage beta 1- and beta 2-adrenoceptor occupancy of metoprolol in plasma was 5-15% less than after administration of the conventional formulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Extent of beta 1- and beta 2-receptor occupancy in plasma assesses the antagonist activity of metoprolol, pindolol, and propranolol in the elderly

We estimated antagonist activity of metoprolol, pindolol, and propranolol in elderly cardiovascular patients by determining the extent to which the drugs occupied rabbit lung beta 1- and rat reticulocyte beta 2-adrenoceptors in plasma samples during drug treatment. The randomized, double-blind, crossover study was carried out by administering twice daily 100 mg metoprolol, 5 mg pindolol, and 80 mg propranolol for 7 days to 20 hypertensive subjects with a mean age of about 70 years. A 2-week interval was kept between administration of the different regimens. Receptor occupancy was measured at 1 hour before and 2 hours after administration of the last dose of each regimen by adding rabbit lung beta 1- and rat reticulocyte beta 2-receptors to plasma samples and by labeling the receptors with a radiolabeled beta-antagonist, (-)-[3H]CGP-12177. The results and conclusions were the following: (a) The extent to which metoprolol, pindolol, and propranolol occupied rabbit lung beta 1- and rat reticulocyte beta 2-adrenoceptors in plasma samples estimated accurately the intensity of beta-receptor antagonism in the patients who did not tolerate physiological and pharmacological tests measuring the degree of beta 1- and beta 2-adrenoceptor blockade. (b) The mean beta 1- and beta 2-receptor occupancy of pindolol and propranolol varied between 76% and 99% during the treatments. The mean beta 1-receptor occupancy of the metoprolol regimen varied between 54% and 92%, and its beta 2-receptor occupancy varied between 6% and 38%. Thus the antagonist activity of the metoprolol regimen differed significantly from that of the other regimens (ANOVA for repeated measures, p < 0.05 and 0.001, for the beta 1- and beta 2-occupancy, respectively). (c) The extent of beta 1- and beta 2-receptor occupancy in plasma samples was in conformity with the literature on the intensity, selectivity, and duration of beta-blockade after similar drug doses. (d) The data on the receptor occupancy of beta-blocking drugs in plasma samples appear to be valuable in analyzing their effects, and it may be a method for optimizing drug therapy for aged cardiovascular patients.