Terbutaline

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Terbutaline is a β2-adrenergic receptor agonist which acts to block smooth muscle activity in the dog[1].

It is frequently used for human sufferers of asthma.

This drug is acts as a tocolytic (postpones uterine contractions during labor) as well as a fast-acting bronchodilator, causing relaxation of proximal and distal airways, similar in effect to aminophylline and diltiazem, but whose mechanism of action differs[2].

In dogs it is indicated for respiratory distress syndrome where it may improve symptoms in acute lung injury by recruiting damaged pulmonary capillaries, leading to increased lung endothelial permeability.[3].

Terbutaline has also been show to reduced arterial blood flow and mucosal volume in the nasal mucosa in dogs[4], implicating its benefits in chronic rhinitis cases[5].

Toxicosis has been reported in dogs from overdoses or accidental ingestion and symptoms include lethargy, tachycardia, tachypnea, and muscle tremors[6].

These effects can be mitigated by propranolol.

References

  1. Wang D et al (1992) Terbutaline acts at multiple sites to inhibit bronchoconstriction induced by dry air in canine peripheral airways. Am Rev Respir Dis 145(6):1295-1300
  2. Akhtar S et al (1999) Differential bronchodilatory effects of terbutaline, diltiazem, and aminophylline in canine intraparenchymal airways. Crit Care Med 27(8):1551-1556
  3. Lee JW (2009) beta2 adrenergic agonists in acute lung injury? The heart of the matter. Crit Care 13(6):1011
  4. Lacroix, JS et al (1995) Beta-adrenergic mechanisms in the nasal mucosa vascular bed. Eur Arch Otorhinolaryngol 252:298–303
  5. Wang M & Lung M (2003) Adrenergic mechanisms in canine nasal venous systems. Br J Pharmacol 138(1):145-155
  6. Gustafson BW (1994) Terbutaline toxicosis in a dog. J Am Vet Med Assoc 204(12):1922-1923