Beta, agonists effects

A pure alpha agonist will cause reflex bradycardia in a subject with intact cardiac innervation, but no change in hean rate if this innervation is severed, eg, in a heart transplant patient. The other drugs listed have direct beta agonist effects and will increase heart rate in the denervated heart. The answer is (D). 

Drug Y causes tachycardia that is not significantly influenced by any of the blockers therefore, drug Y must have a direct beta-agonist effect on the heart. The answer is (C). 

J. P. Hanrahan and co-workers, Beta-Agonists and Their Effects on Animal Growth and Carcass Quality, Elsevier Apphed Science, London, 1987, pp. 106-118. 

Taylor DR, Sears MR, Herbison GP, et al. (1993) Regular inhaled beta agonist in asthma effects on exacerbations and lung function. Thorax. 48,134—138. 

LTB4 is a potent bronchoconstrictor, as are several other leukotrienes. A 5-lip-oxygenase inhibitor, Zileuton, is approved for therapy of asthma (though it is not much used for this purpose) as is a leukotriene blocker, montelukast, marketed as Singulair. Singulair is widely used by asthmatics as a preventive for asthma attacks. Certain corticosteroids are employed for the same purpose. Neither montelukast nor the steroids are effective in terminating an established asthmatic attack. Beta agonists are employed for that purpose (see chapter 17). 

Orciprenaline is a partially selective adrenoceptor-agonist and hence it is more likely to have effects on the cardiovascular system, such as arrhythmias, than the selective adrenoceptor-agonists, such as salbutamol, terbutaline and the long-acting beta-agonists salmeterol and formoterol. Orciprenaline is available only as tablets or syrup and can be prescribed to 4-year-old children. 

A failure to detect these classes of ADE may have serious consequences, as the ADE itself may be disabling or even life threatening, but even when it is relatively trivial it may be a reason for the patient s discontinuing effective treatment, which in turn may cause a deterioration in their condition. An example would be the patient who discontinues the treatment of his asthma with a beta-agonist because of tremor and then goes into status asthmaticus, with fatal consequences. 

Previous trials with the beta-agonist salmeterol had given an average difference from placebo in PEF of 371/min while the effect of inhaled steroids was of the order of 251/min and A was chosen as a proportion of those effects. 

Oral or subcutaneous administration is usually associated with more side effects. However, when administered orally or subcutaneously, beta agonists may reach the more distal branches of the airway to a greater extent. The bronchioles are usually constricted during an asthmatic attack, and the drug may not reach the distal respiratory passages when administered by inhalation. 

Evidence also suggests that leukotriene inhibitors can be combined with other drugs (glucocorticoids, beta agonists) to provide optimal management in specific patients with asthma and COPD.11,60 In particular, it appears that these drugs may enhance the anti-inflammatory effects of glucocorticoids, and may therefore provide therapeutic effects at a relatively... 

Abramson MJ, Walters J, Walters EH. Adverse effects of beta-agonists are they clinically relevant Am J RespirMed. 2003 2 287-297. 

Wraight JM, Smith AD, Cowan JO, et al. Adverse effects of short-acting beta-agonists potential impact when anti-inflammatory therapy is inadequate. Respirology. 2004 9 215-221. 

The potential for consumer exposure to residues of tranquillisers and beta-agonists has been tested intensively over the past twenty years. This followed evidence of illegal drug availability and usage. These substances could have immediate effect on health if consumed in large amounts. Action was taken to protect consumers. Surveillance continues to ensure that no detectable contamination of the food supply occurs with these substances (see, for example, VMD, 1995). 

Tachycardia is an increase in the heart rate over 100 per minute. This can be due to excessive use or side-effects of a beta-agonist. It can be induced by anxiety and panic, which a patient may experience during an asthma attack. Tachypnoea is an increase in the respiratory rate due to airway narrowing and constriction, hence the body will increase its respiratory rate to try to increase the intake of oxygen. 

BETA-BLOCKERS COCAINE Risk of hypertensive crisis Cocaine produces both alpha- and beta-adrenergic agonist effects selective beta-blockade leads to unopposed alpha-agonism (vasoconstriction) Avoid concurrent use... 

Non-selective beta-agonists (ephedrine, orciprenaline) are now rarely used because of the higher incidence of cardiovascular side-effects by their action on beta-1 receptors... 

Muscle cramps have been reported in patients taking beta-blockers with partial agonist activity (273) it has been suggested (274) that this might be a beta2-partial agonist effect, although this has not subsequently been... 

Tomlinson B, Cruickshank JM, Hayes Y, Renondin JC, Lui JB, Graham BR, Jones A, Lewis AD, Prichard BN. Selective beta-adrenoceptor partial agonist effects of pindolol and xamoterol on skeletal muscle assessed by plasma creatine kinase changes in healthy subjects. Br J Clin Pharmacol 1990 30(5) 665-72. 

Sears MR. Adverse effects of beta-agonists. J Allergy Clin Immunol 2002 110(Suppl 6) S322-8. 

The beta-adrenoceptor agonist effect is sufficient to cause fetal tachycardia when isoxsuprine is given intravenously in late pregnancy, although one large survey suggested that it may be better tolerated by the mother (as regards cardiac and stimulant effects) than salbutamol (SED-12, 313). The fact that maternal blood... 

Taylor DR, Wilkins GT, Herbison GP, Flannery EM. Interaction between corticosteroid and beta-agonist drugs. Biochemical and cardiovascular effects in normal subjects. Chest 1992 102(2) 519-24. 

Enantiomer Preparations of Inhaled Drugs. There has been much interest in the differences in effects of enantiomers of many medications, and beta agonist adrenergic bronchodilators have received much attention. Evidence suggests that the (R)-enantiomer of albuterol is mainly responsible for bronchodilation while the (S)-enantiomer may stimulate airway reactivity. Data suggest, however, that after aerosol delivery, the systemic absorption for (R)-albuterol is faster than for (S)-albuterol and that, conversely, the lung retention of (S)-albuterol is longer, which may be detrimental [29]. The extent to which enantiomers will displace racemic preparations is not yet determined. 

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