Effects of acepromazine maleate, isoxsuprine hydrochloride and prazosin hydrochloride on laminar microcirculatory blood flow in healthy horses

An Analgesic Evaluation of Isoxsuprine in Horses

“…Although the pharmacological activity of isoxsuprine was not tested after evaporation and reconstitution with ethanol, it is unlikely that these processes would have affected its activity. This is because profuse sweating was observed as it was reported after intravenous injection of isoxsuprine in horses (Matthews et al, 1986;Harkins et al, 1996;Adair et al, 1997). Hence, although physiological responses to isoxsuprine were noticed, it failed to increase mechanical nociceptive thresholds in horses.…”

“…In vivo, increased thermographic temperature of the cannon bone, fetlock and coronary band of forelimbs of horses has been reported after oral isoxsuprine administration, which suggests that isoxsuprine increases blood flow in the distal forelimbs of horses (Rose et al, 1983;Deumer et al, 1991). However, oral and intravenous administration of isoxsuprine did not modify digital or laminar blood flow in healthy horses (Adair et al, 1997;Ingle-Fehr and Baxter, 1999). Harkins et al (1996) reported diminished thermographic temperature of the forelimbs with a tendency, but with no significant difference, to increase cutaneous blood flow in the pastern of horses given isoxsuprine intravenously.…”

Treatment of Acute Laminitis

“…Phenoxybenzamine has been used to a limited extent clinically. Experimentally, acepromazine increases digital and lamellar blood flow in normal horses (Adair et al 1994(Adair et al , 1997Ingle-Fehr and Baxter 1999), but it has not been tested in horses with induced laminitis. However, due to its availability, widely accepted safety and subjective clinical impressions of efficacy, it is the most widely used vasodilator in the treatment of clinical laminitis.…”

“…Isoxsuprine is an effective dilator of isolated palmar digital vessels in vitro (Baxter et al 1989), but conflicting data regarding its ability to improve peripheral blood flow (Rose et al 1983;Harkins et al 1996;Adair et al 1997;Ingle-Fehr and Baxter 1999) and the inability to detect isoxuprine in the plasma after oral dosing raise questions about its efficacy (Matthews et al 1986;Harkins et al 1998). However, some clinicians have subjectively observed improvements in horses with clinical laminitis.…”

“…Pentoxyphylline is the principal drug that has been investigated, although isoxuprine is reported to have similar properties. However, experimentally, neither drug has been shown to increase lamellar blood flow (Adair et al 1997;Ingle-Fehr and Baxter 1999).…”