Tying up, also known as exertional rhabdomyolysis, is a condition in horses where strenuous exercise leads to muscle damage and pain. The condition gets its name from the stiff, cramped gait that affected horses display. Tying up occurs when glycoside stores in muscle cells break down during intense exercise, disrupting calcium regulation in the cells. This leads to muscle stiffness and cramping.
One of the blood markers used to diagnose tying up is serum glutamic oxaloacetic transaminase (SGOT). This enzyme is released into the bloodstream when muscle cells are damaged. In horses with tying up, SGOT levels are often extremely elevated, indicating significant muscle injury.
Dantrolene (trade name Dantrium) is a muscle relaxant medication commonly used to treat tying up in horses. Dantrolene works by inhibiting calcium release in muscle cells. This reduces muscle contraction and cramping. By decreasing muscle damage, dantrolene helps lower circulating SGOT back to normal levels.
The recommended dosage of dantrolene for horses with tying up is 2.5mg/kg intravenously. Effects are seen within 30 minutes. Dantrolene does not cure tying up but helps relax the muscles and prevent further muscle damage during an episode. This provides relief to the horse and allows SGOT levels to gradually recover.
The recommended dosage of oral dantrolene for horses with tying up is 25-30 mg/kg once daily. The oral formulation of dantrolene is typically used for preventative treatment in horses prone to episodes of tying up, rather than acute treatment during an episode. Oral dantrolene takes longer to achieve therapeutic blood levels compared to intravenous administration. However, oral dosing provides sustained muscle relaxation when given prophylactically. For acute tying up episodes, intravenous dantrolene is preferred due to its quicker onset of action. But the oral form can be useful in preventing muscle cramping in horses with a history of exertional rhabdomyolysis. The oral dantrolene dosage should be tailored to each horse based on its individual response and tolerance. With proper administration, it can help keep SGOT levels in the normal range by reducing muscle damage from tying up
Along with medication, management of tying up includes rest, correcting electrolyte imbalances, and modifying exercise programs to prevent future episodes. Dantrolene is a useful tool to minimize muscle damage and pain if a horse ties up during activity. By reducing cramping and injury to muscle cells, dantrolene can help return SGOT levels back to normal ranges. It is an important treatment option for this painful condition in horses.