Terbutaline, asthma

G. Persson, O. Pahlm, Y. Gnosspelius, Oral Bambuterol versus Terbutaline in Patients with Asthma , Curr. Then Res. 1995, 56, 457 - 465. 

The majority of the marketed products are used for asthma and COPD. Typical agents that are used for these indications are fl2-agonists such as salbutamol (albuterol), Terbutalin or formoterol, corticosteroids such as budesonide, FUxotide or beclomethasone and mast-cell stabilizers such as sodium cromoglycate or nedocromil. 

Bronchodilation. P2-Adrenocep-tor-mediated bronchodilation (e.g., with terbutaline, fenoterol, or salbutamol) plays an essential part in the treatment of bronchial asthma (p. 328). 

Terbutaline A bronchodilatorfor bronchial asthma and for reversible bronchospasm that may occur with bronchitis and emphysema. 

Therapeutically, terbutaline and albuterol are used to treat bronchial asthma and bronchospasm associated with bronchitis and emphysema (see Chapter 39). 

Inhaled salmeterol has a pharmacological half-life in excess of 12 hours, much longer than either albuterol or terbutaline. The likely basis for this long half-hfe is that the long lipophilic tail of salmeterol promotes retention of the molecule in the cell membrane. Its long duration of action makes salmeterol particularly suitable for prophylactic use, such as in preventing nocturnal symptoms of asthma. Because of its relatively slow onset of action, salmeterol should not be used to treat acute symptoms. 

Terbutaline, albuterol, salmeterol and other Pj-adrenoceptor agonists are used primarily in the management of asthma. Terbutaline and albuterol have very rapid onset of action and are indicated for acute symptom rehef Salmeterol, in contrast, has a slow onset of action but a long duration of action. Salmeterol is thus used as prophylactic therapy only, not to reverse acute symptoms. 

One of the most important uses of sympathomimetic drugs is in the therapy of bronchial asthma. This use is discussed in Chapter 20. Nonselective drugs (epinephrine), -selective agents (isoproterenol), and B2-selective agents (albuterol, metaproterenol, terbutaline) all are available for this indication. Sympathomimetics other than the 32-selective drugs are now rarely used because they are likely to have more adverse effects than the selective drugs. 

Of these agents, only terbutaline is available for subcutaneous injection (0.25 mg). The indications for this route are similar to those for subcutaneous epinephrine—severe asthma requiring emergency treatment when aerosolized therapy is not available or has been ineffective—but it should be remembered that terbutaline s longer duration of action means that cumulative effects may be seen after repeated injections. 

Philip-Joet, F., Bruguerolle, B., Lagier, F., et al. Effects of a constant dose rate of terbutaline on circadian peak expiratory flow, heart rate and systolic arterial pressure in patients with asthma exacerbation. Respiration 59 197—200, 1992. 

Salbutamol (Ventolin Accuhaler) - management of asthma, bronchospasm and/or reversible airways obstruction (also terbutaline, formoterol, salmeterol, etc.). 

Q1 The most commonly used reliever in asthma therapy is a short-acting bronchodilator, such as the beta-2-agonists (/ -agonists) salbutamol or terbutaline. These are safe and effective agents for mild to moderate symptoms and are taken directly into the respiratory tract via an inhaler device. 

INHALATIONAL- HALOTHANE TERBUTALINE, THEOPHYLLINE Cases of arrhythmias when these bronchodilators are co-administered with halothane Possibly due to sensitization of the myocardium to circulating catecholamines by the volatile anaesthetics to varying degrees Risk of cardiac events is higher with halothane. Desflurane is irritant to the upper respiratory tract, and t secretions can occur and are best avoided in patients with bronchial asthma. Sevoflurane is non-irritant and unlikely to cause serious adverse effects... 

Pj-selective agonists such as prenalterol (Figure 10.5) or dobutamine are used to stimulate heart contractility and heart rate in patients that exhibit too low blood pressure. P2-Selective agents such as terbutaline find application for relaxation and dilatation of the bronchi in the treatment of asthma or chronic obstmctive lung disease, and in the suppression of premature labour. The mechanism of P-receptor-induced relaxation of smooth muscle - cAMP-mediated phosphorylation and inhibition of myosin light chain kinase - has been described before. 

A female subject took several tablets of terbutaline during a severe night attack of asthma and died the next morning. The following postmortem tissue concentrations were reported serum 0.014pg/ml, heart 0.036 pg/g, kidney 0.054 pg/g, liver0.055 pg/g, lung 0.026 pg/g, muscle 0.063 pg/ g (J. G. Leferink et al., J. analyt. Toxicol., 1978,2, 86-88). 

Pj effects, used in asthma, or to relax the uterus, include salbutamol, terbutaline, fenoterol, pirbuterol, reproterol, rimiterol, isoxsuprine, orciprenaline, rit-odrine. 

Salbutamol, fenoterol, rimiterol, reproterol, pir-buterol, salmeterol, ritodrine and terbutaline are P-adrenoceptor agonists that are relatively selective for p2-receptors, so that cardiac (chiefly p -receptor) effects are less prominent. Tachycardia still occurs because of atrial (sinus node) p -receptor stimulation the P2-adrenoceptors are less numerous in the ventricle and there is probably less risk of serious ventricular arrhythmias than with the use of nonselective catecholamines. The synthetic agonists are also longer-acting than isoprenaline because they are not substrates for catechol-O-methyltransferase, which methylates catecholamines in the liver. They are used principally in asthma, and to reduce uterine contractions in premature labour. 

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