Terbutaline may cause skeletal muscle tremor, but bronchospasm, contrary to its pharmacological effects, is rare. Ayed et al. reported a patient using terbutaline nebulization to cause dyspnea, cough, wheezing, and hypoxia (85% oxygen saturation), tachycardia ( 110 beats per minute)[1]. All short-acting β2 -adrenoceptor agonists approved by the FDA have warnings about causing paradoxical bronchospasm [4], and the instructions for terbutaline sulfate also suggest that the drug may cause bronchospasm, but the incidence rate the mechanisms are tillunknown.
Some studies suggest that bronchospasm caused by β2 -adrenoceptor agonists may be mediated by IgE, and that salbutamol, terbutaline, and pibuterol share common structural features: a tert-butyl group attached to a nitrogen atom may explain that they can all bind to proteins to produce IgE and cause bronchospasm [11–12]. Other studies have suggested that β2 -adrenoceptor agonists induced bronchospasm may be related to inhalant excipients (propellants and surfactants), preservatives (benzalkonium bromide), osmotic pressure, and/or pH [1,8]. Benzalkonium bromide has been mentioned several times in preservatives [13–15], and ededidine disodium has also been reported [16] .In this case, the patient used terbutaline sulfate nebulizate, which does not contain preservatives and excipients, but its excipients contain ededine disodium [1], which may be the cause of bronchospasm. In addition, osmotic pressure of nebulized fluids can cause bronchoconstriction, hypertonic buffers have been shown to cause the release of histamine from normal human basophils and mast lung cells, and both hypotonic or hypertonic saline solutions can induce bronchoconstriction[1]. The 2 ml of sterile water used as a nebulization dilution in this patient may also be related to the hypotonic nature of this nebulization solution.
β2 -adrenoceptor agonists are first-line agents for the treatment of airway spasm diseases such as asthma and chronic obstructive pulmonary disease. However, we should keep vigilance during use. They may lead to paradoxical bronchospasm, a serious adverse reaction, which is extremely rare but fatal. This case shows that terbutaline can rapidly cause bronchospasm after nebulization. The nebulized diluent used at the same time can also cause bronchoconstriction. The use of sterile water for injection should be avoided during the clinical use of terbutaline, and close monitoring is also required.