Beta-adrenergic blockade. An update

Betaxolol eye drops. A clinical trial of safety and efficacy

OBJECTIVE

To study the cardiopulmonary safety and ocular hypotensive efficacy of topical betaxolol hydrochloride 0.5% (a selective beta-1 blocker) in patients with unacceptably elevated intraocular pressure (IOP) and respiratory dysfunction.

METHODS

Thirty-one patients with poor control of elevated IOP were selected on the basis of coexistent respiratory disease which could be exacerbated by beta-antagonist administration and/or who had past adverse reactions to topical timolol. Using an open-label design, the ophthalmic, cardiovascular and pulmonary parameters of these patients were measured before betaxolol therapy, for four hours immediately after the first administration of the drug, and after one, four and 12 weeks of therapy. The screening and 12-week examinations included a bronchial challenge with methacholine, a non-specific bronchoconstricting agent.

RESULTS

IOP reduction was significant at all time points measured after first instillation of betaxolol, with a mean maximum fall of 8.4 (SD, 3.2) mmHg (95% Cl -9.545 to -7.261) from a baseline mean IOP of 23.9 (SD, 3.8) mmHg. Over 12 weeks of therapy, the mean reduction from baseline in IOP was 3.9 (SD, 2.6) mmHg (95% Cl -4.908 to -2.988). After first instillation of betaxolol, mean arterial pressure (MAP) fell transiently to a mean maximum fall of 3.9 (SD, 9.3) mmHg (95% Cl -7.159 to -0.582), from a mean baseline MAP of 107.7 (SD, 9.4) mmHg. Heart rate did not change. There were no changes in any of the respiratory parameters measured: forced expiratory volume in one second, forced vital capacity and peak expiratory flow rate. Over 12 weeks of betaxolol therapy, there were no changes in any of the above systemic parameters and no change in mean bronchial reactivity as measured by methacholine challenge. Of the 31 patients, who included 13 patients with previous intolerance to timolol (a non-selective beta-antagonist), only one showed intolerance to betaxolol.

CONCLUSIONS

Betaxolol appears to be an effective and well tolerated ocular hypotensive agent in a typical glaucoma population, which includes many patients with cardiopulmonary disease. Individual intolerance to betaxolol will continue to occur and care is always required when patients with cardiac or respiratory dysfunction are exposed to any beta-antagonist.

Comparison of bisoprolol and diazepam in the treatment of cardiac neurosis

In order to compare the beta blockers bisoprolol and diazepam in the treatment of cardiac neurosis, 40 patients (16 males and 24 females, mean age: 39 +/- 11 years) were examined in a double-blind, crossover study. Following a 4-week placebo period, patients were randomized to receive either bisoprolol 10 mg daily or diazepam 5 mg twice daily for 4 weeks. After a second 4-week washout period on placebo, patients were switched to the alternative regimen for a further 4 weeks. At the end of the placebo periods and during each phase of treatment, the following parameters were evaluated: somatic symptoms by self-assessment questionnaire, anxiety state by Hamilton rating scale, reaction time to both acoustic and visual stimuli, blood pressure, and heart rate. Both treatments were effective in reducing somatic symptoms of cardiac neurosis, but bisoprolol was significantly more effective than diazepam (p less than 0.01). On the contrary, diazepam was superior to bisoprolol in improving the Hamilton scale related to psychic symptoms. Only diazepam prolonged reaction times. Both treatments were well tolerated; however, 12 patients complained of drowsiness and nine of sedation under diazepam. In conclusion, bisoprolol appeared to be as effective as diazepam in the treatment of cardiac neurosis, but with better effects on somatic symptoms and without affecting patients' psychomotor performance.

A comparison of guanfacine, bunazosin, atenolol and nadolol on blood pressure and plasma noradrenaline responses to cold pressor testing

1. The role of the presynaptic adrenoceptor subtypes in man was investigated based on observation of the changes in blood pressure (delta BP) and plasma noradrenaline concentration (delta NA) with the cold pressor test (CPT). 2. The CPT was well reproducible for BP and NA when performed at a 2 week interval in patients with mild hypertension. 3. After administration for 4 weeks, guanfacine (Gf; alpha 2-adrenoceptor agonist) decreased the delta NA response to CPT. 4. After administration for 2 or 4 weeks, bunazosin (Bu; alpha 1-adrenoceptor antagonist) atenolol (At; beta 1-adrenoceptor antagonist) and nadolol (Nd; non-selective beta-adrenoceptor antagonist) did not affect the delta NA response to CPT. 5. Both Gf and Bu decreased the systolic blood pressure response (delta SBP) to CPT after 4 weeks of the administration. Neither At nor Nd significantly changed the delta SBP response to CPT. 6. It is likely that Gf stimulated the presynaptic alpha 2 adrenoceptors at the sympathetic nerve endings as well as the central alpha 2 adrenoceptors, inhibiting the release of noradrenaline. It is unlikely that Bu, At and Nd exerted any clearly defined action on the presynaptic adrenoceptors in human hypertensive subjects.

Advances in cardiovascular pharmacological therapy

Progress in the pharmacological management of cardiovascular disease has been accompanied by the appearance of drugs with never before seen capabilities to alter human physiological processes. The widespread use of these potent agents poses a challenge to the oral and maxillofacial surgeon attempting to safely manage patients in the ambulatory setting. This article reviews the field of contemporary cardiovascular pharmacotherapy from the aspect of how it affects the practice of oral and maxillofacial surgery.

Clinical safety and efficacy of celiprolol

The management of essential hypertension requires therapeutic selections that are not only effective in reducing diastolic blood pressure but are also tailored to the individual patient, with minimal effect on patient demographics, concurrent illnesses, and cardiovascular risk factors. Celiprolol hydrochloride is a new highly cardioselective vasodilating beta-adrenoceptor antagonist that has been proven effective and safe for the treatment of essential hypertension. It is comparable to other therapies in blood pressure control while demonstrating an excellent safety profile, favorable hemodynamic activity, and minimal effects on other cardiovascular risk factors. Celiprolol may offer the physician a unique therapeutic alternative.

Stereoselective hemodynamic effects of (R)-and (S)-propranolol in man

In a randomized, double-blind, placebo-controlled, cross-over study 24 healthy volunteers were examined before and 2 h after oral administration of 80 mg (R,S)-, 40 mg (R)- and 40 mg (S)-propranolol.HCl; 8 of them received placebo in an additional run. During exercise on a bicycle ergometer and a rest period the rate pressure product was decreased by 80 mg (R,S)-propranolol.HCl (-32.8% p less than 0.0001) and 40 mg (S)-propranolol.HCl (-32.3%; p less than 0.0001), whereas 40 mg (R)-propranolol.HCl as well as placebo showed no effect. Corresponding binding inhibition experiments using (-)-(125I)iodocyanopindolol in a sarcolemma-enriched cardiac membrane preparation yielded a eudismic ratio of 179 for (S)- over (R)-propranolol. 2 h after oral application, stereospecific HPLC analysis revealed different individual concentrations in plasma of (R)- 22.3 +/- 21.7 ng/ml) and (S)-propranolol (30.4 +/- 26.9 ng/ml) when 80 mg of (R,S)-propranolol.HCl was administered. The plasma levels were similar when 40 mg of the pure enantiomer of (R)- (22.7 +/- 20.3 ng/ml) or (S)-propranolol.HCl (28.7 +/- 22.5 ng/ml) was applied. (R)- and (S)-propranolol are two substances with different pharmacodynamic and pharmacokinetic properties. As there are methods available to produce the optically pure enantiomers, they should be used rather than the racemic mixture.

Betaxolol

Drugs classified as beta-blockers have proved to be valuable in the treatment of patients with glaucoma. Timolol has become the most widely used ocular hypotensive agent. Actual and potential side effects associated with its non-selective beta-blockade have prevented its use in patients with reactive airways disease, and to a lesser extent, with various cardiovascular conditions. Betaxolol is a relatively selective beta-1 blocker which in most patients is almost as effective as timolol in lowering intraocular pressure, and may be partly additive with dipivefrin. It is probably safer in patients unable to tolerate non-selective beta-blockers. However, it needs to be used with caution in these patients, who are unpredictably susceptible to systemic side effects.

The conundrum of the effect of beta-blockade on myocardial oxygen consumption

The effect of propranolol on myocardial oxygen consumption was studied in in situ canine hearts. In 12 afterload independent isovolumic hearts propranolol increased MVO2 an average of 19 +/- 3% (P less than 0.01) for all peaked developed pressure intervals from 75 to 175 mm Hg, secondary to increased wall stress. In 10 hearts instrumented for computer acquisition of pressure-volume workloops during progressive volume loading on right heart bypass, propranolol decreased preload recruitable stroke work an average of 36% (P less than 0.05). However, propranolol failed to decrease the amount of oxygen consumed for basal metabolism or external mechanical work when MVO2 is indexed for heart rate, heart weight, and stroke work. Therefore, propranolol does not decrease MVO2 for individual contractions and does not affect the energy requirements for basal metabolism, excitation-contraction coupling, and heat generation, in contrast to results obtained with beta agonists.

A double-masked comparison of carteolol and timolol in ocular hypertension

We performed a double-masked study in which 98 patients with ocular hypertension who had been previously treated with timolol received either timolol 0.25% or carteolol 1%, a beta-blocker with intrinsic sympathomimetic activity. The drugs were administered topically twice daily for one month after a one-week washout period. Intraocular pressure was measured at baseline and after one and four weeks of treatment. The appearance of the fundus, external eye, visual fields, tear secretion, blood pressure, and pulse were recorded. Adverse symptoms were elicited using a menu-type questionnaire and an overall judgment of therapy was recorded. Carteolol was as effective as timolol in reducing intraocular pressure. There were significantly fewer patients reporting adverse events overall (P = .019), and eye irritation specifically (P = .02), in the group treated with carteolol.

The beta 1- and beta 2-adrenoceptor affinity of atenolol and metoprolol. A receptor-binding study performed with different radioligands in tissues from the rat, the guinea pig and man

The radioligand binding technique was used to perform a systematic investigation of the beta 1- and beta 2-adrenoceptor affinity of atenolol and metoprolol in tissues from the rat, the guinea pig and man. Radioligands, [125I](+/-)hydroxybenzylpindolol, [125I](-)pindolol, [3H](-)dihydroalprenolol and [3H](-)CGP12177, with different degrees of lipophilicity were used in the binding experiments. In membrane preparations of rat ventricular myocardium and uterus, the number of specific binding sites was similar when comparing experiments performed with the different radioligands. The percentage of the beta 1- and beta 2-adrenoceptor subpopulations in the tissues studied was not dependent on the radioligand or displacing compound used. Furthermore, the affinity of metoprolol and atenolol for beta 1- and beta 2-adrenoceptors was independent of the radioligand used or the tissue studied. The beta 1-adrenoceptor affinity of metoprolol was about 6-7 times higher than that of atenolol, while the beta 1-adrenoceptor selectivity was similar (about 30-fold) for the two beta-blockers. It is concluded that the physical-chemical properties of the radioactive ligands and beta-blockers studied do not affect the results obtained from beta-adrenoceptor-binding experiments in cellular membrane fractions. The beta 1- and beta 2-adrenoceptor affinities did not change in any experiments performed in tissues from the rat, the guinea pig and man for either atenolol or metoprolol.

Antihypertensive therapy and the concept of total cardiovascular protection

Drug-induced reduction of elevated blood pressure decreases cardiovascular mortality and morbidity in patients with moderate and severe hypertension. Furthermore, antihypertensive drug studies in mild hypertensive subjects (diastolic blood pressure 90 to 104 mm Hg) have shown protection against stroke, left ventricular hypertrophy, congestive heart failure and progression of renal damage, as well as improved patient longevity. The Hypertension Detection and Follow-up Program trial, recently carried out in the U.S., documented reduced coronary artery disease events (fatal and nonfatal) in special drug-treated patients with mild hypertension. From the standpoint of practical management and considering the ubiquity of essential hypertension, a modified stepped-care regimen advocating initial drug therapy with a beta blocker and addition of low-dose thiazide diuretic when necessary constitutes a judicious approach for widespread application. Although there are 8 orally active beta blockers currently approved in the U.S. for clinical use in systemic hypertension, only acebutolol possesses all of the salutary pharmacologic properties of cardioselectivity, intrinsic sympathomimetic activity and hydrophilicity, thereby making this compound an effective and safe beta-blocking agent for first-order management of a broad segment of the hypertensive population.