Colic drug proves effective in relieving heaves

The characteristic tucked-up look of a horse with heaves. Often, a line of abdominal muscle is visible along each side, called heave lines.
The characteristic tucked-up look of a horse with heaves. Often, a line of abdominal muscle is visible along each side, called heave lines.

A drug commonly used to treat spasmodic colic has been shown to relieve bronchial spasms in horses suffering from heaves, also known as recurrent airway obstruction.

Heaves, also known as chronic obstructive pulmonary disease (COPD), is a common problem of stabled horses.

It is initiated by inhaled stable dust, which contains agents that cause lung inflammation, including fungal spores, bacteria and endotoxin.

Severely affected animals show signs such as dilated nostrils, nasal discharge, and excessive chest movement. They may be incapable of any athletic activity.

Mild cases may appear to breathe normally and require further investigation to confirm the diagnosis. However, most cases fall somewhere between the two extremes.

Inhalation of stable dust by a susceptible horse leads to spasm of the airways and increased mucus production.

In many cases, providing good ventilation, housing the horse on dust-free bedding and feeding low-dust forage may be all that is needed.

Cases with severe respiratory distress may respond to bronchodilators. Atropine can be used to dilate the airways, but repeated administration of atropine may have an adverse effect on gut motility.

The latest issue of Equine Science Update reports on research in the area by Professor Laurent Couëtil and colleagues at Purdue University College of Veterinary Medicine, in West Lafayette, Indiana.

It has shown that N-butylscopolammonium bromide (NBB) – also known as Buscopan, N-butylscopolamine bromide, and hyoscin N-butylbromide – is effective at relieving bronchoconstriction in horses with RAO.

The double blind, placebo-controlled, randomised crossover trial involving nine horses with heaves. All had transpulmonary pressure (∆P(L)) greater than 15mmHg.

The horses were divided into two groups. The first was treated with NBB, the other with 0.9% saline as control.  Transpulmonary pressure ∆P(L) as a measure of lung function, and clinical scores were recorded before treatment and at intervals up to 120 minutes after treatment.

After a six week “wash out” period the procedures were repeated with the treatment groups swapped around.

The researchers found that NBB produced a significant improvement in both clinical score and lung function.

A significant decrease in ∆P(L) was first detected two minutes after administration. Maximum response occurred 10 minutes after administration. By 60 and 120 minutes after treatment, ∆P(L) no longer differed significantly between NBB and placebo.

The research team concluded that N-butylscopolammonium bromide was a potent bronchodilator, having maximum effect 10 minutes after intravenous administration. The effect wore off within 1 hour of drug administration.

Effects of N-butylscopolammonium bromide on lung function in horses with recurrent airway obstruction.
L Couetil, J Hammer, M Miskovic Feutz, N Nogradi, C Perez-Moreno, K Ivester.
J Vet Intern Med. 2012 Nov;26(6):1433-8.
doi: 10.1111/j.1939-1676.2012.00992.x.

Equine Science Update



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