Horses colic

Flunixin is registered or is under development in many countries for use in horses, cattle, and swine for treatment of equine colic, musculoskeletal disorders, acute endotoxin-induced mastitis in cattle, and respiratory disease (89-91). It is administered orally or parenterally for a maximum of 5 successive days (92). Flunixin is a genotoxic but not carcinogenic compound. Its mechanism of action is believed to be via the inhibition of cycloxygenase to reduce the presence of arachidonic acid metabolites produced during inflammation (93). 

Proudman, C.J., French, N.J. and Trees, A.J. (1 998) Tapeworm infection is a significant risk factor for spastic colic and ileal impaction colic in the horse. Equine Veterinary journal 30, 194-199. 

Equine platelets rq >ear to be highly reactive in vivo, however, the bleeding time for horses is 3 to 4 times longer than that of other species. The horse suffers from several thrombotic diseases including fimmiboembohe colic and iliac thromboembolism. Horses also readily... 

Proudman C J, Edwards G B 1992 Vaiidation of a centrifugation/fiotation technique for the diagnosis of equine cestodiasis. Veterinary Record 131 71-72 Proudman C J, Matthews J B 2000 Control of Intestinal parasites in horses, in Practice 22 90-97 Proudman C J, French N P, Trees A J 1998 Tapeworm infection as a significant risk factor for spasmodic colic and Ileal impaction colic in the horse. Equine Veterinary Journal 30 194-199... 

The broad-spectrum anthelmintic nitazoxanide has been undergoing efficacy trials in the USA for the treatment of EPM (Vatistas et al 1999). This drug is currently used to combat intestinal parasites of humans in developing countries and in patients with the acquired immimodeficiency syndrome complicated by secondary protozoal infections. Nitazoxanide is administered daily for 28 days as an oral paste. The side-effects of this drug are more serious than with other medications because it kills other parasites in addition to S. neurona. This has led to recommendations for deworming with another anthelmintic prior to starting this treatment (McClure Palma 1999). Nitazoxanide may also cause colic in treated horses. 

The adverse effects of quinidine can be divided into cardiac and non-cardiac manifestations. Depression and paraphimosis are seen in many horses treated with quinidine sulfate and resolve once treatment is discontinued. Gastrointestinal effects include flatulence, which is rarely of clinical significance, and colic and diarrhea, both of... 

Scopolamine is an anticholinergic agent used for the treatment of spasmodic colic it has been shown to inhibit romifidine-induced bradyarrhythmias (Marques et al 1998). Unlike atropine, scopolamine does not induce an initial bradycardia (Grainger Smith 1983) and decreased gastrointestinal motility lasts only 20-30 min in horses (Roelvink et al 1991). The use of scopolamine in the face of life-threatening bradycardias in horses has not been established. 

TTie ability of certain drugs to cross the ocular and nasolacrimal epithelium means that these drugs are to some extent absorbed systemically. The degree to which this occurs in the horse has not been investigated extensively. However, topical atropine has been recognized as causing transient ileus, particularly in foals, and has been implicated in a very small number of fatal colic cases in adult horses (Brooks 1999). Dexametha-sone has been detected in the serum of horses 24 h after cessation of administration of a 0.1% ointment three times a day (Speiss et al 1999) and trainers of competition horses should be made aware of the possibility of forensic detection of topically administered ophthalmic drugs. 

Ileus is a potential side-effect of the systemic absorption of ophthalmic atropine in the horse. This may be an idiosyncratic response affecting only a few individual horses but all atropine-treated horses should be monitored for signs of colic. 

The NSAIDs are amongst the most commonly prescribed agents for use in horses. Musculoskeletal pain and inflammation are the most common indications for chronic administration of NSAIDs to horses, with phenylbutazone being the NSAID used most frequently for that purpose. Flunixin meglumine is most commonly administered for relief of acute gastrointestinal distress or colic, fever and soft-tissue inflanunation. In addition. 

Flunixin meglumine, a nicotinic acid derivative, is a potent analgesic commonly used to control severe intestinal pain or colic in the horse. In this setting, it has effects comparable to opioid analgesics without inducing the unwanted side-effects commonly observed with opiates in horses, such as CNS excitation and ileus (Boothe 1995). In addition, flunixin meglumine has been shown in several experimental models to produce antien-dotoxic effects at doses lower than those used for anti-inflammatory effects (Jackman et al 1994, Moore et al 1986, Templeton et al 1987). 

The hemodynamic effects of the phenothiazines can be significant. Acepromazine is associated with decreased systolic, mean and diastolic blood pressures (Marroum et al 1994). The heart rate is usually unchanged after acepromazine administration. The fall in blood pressure is a result of decreased total peripheral resistance caused by antagonism of adrenoceptors in the vasculature. Despite a fall in blood pressure, administration of acepromazine (0.05 mg/kg) can be associated with improved cardiac output, as stroke volume increases with the decrease in peripheral resistance (Steffey et al 1985). This would not be the case in a horse that is volume depleted as a result of colic or blood loss and acepromazine is contraindicated in these cases because of the potential for the development of extreme hypotension and cardiovascular collapse. There can be significant individual variability in the degree of hypotension that results from the... 

Lidocaine is used in cardiovascular medicine for its antiarrhythmic properties (see Ch. 12). More recently, studies have looked at the i.v. administration of lidocaine to horses with colic (see Ch. 6). It appears that i.v. lidocaine (without epinephrine (adrenaline)) may have some desirable effects on jejunal distension and peritoneal fluid accumulation and is well-tolerated periop-eratively in horses with colic (Brianceau et al 2002). In addition, i.v. lidocaine reduced the halothane MAC significantly (Doherty Frazier 1998) in ponies. 

Brianceau P, Chevalier H, Karas A 2002 Intravenous lidocaine and small-intestinal size, abdominal fluid, and outcome after colic surgery in horses. Journal of Veterinary Internal Medicine 16 736-741... 

Jochle W 1989 Field trial evaluation of detomidine as a sedative and analgesic in horses with colic. Equine Veterinary Journal Supplement 136 117-120 Jochle W, Moore J N, Brown J et al 1989 Comparison of detomidine butorphanol, flunixin meglumine and xylazine In clinical cases of equine colic. Equine Veterinary Journal Supplement 136 111-116 Johnson C B, Taylor P M 1997 Effects of alfentanll on the equine electroencephalogram during anaesthesia with halothane In oxygen. Research in Veterinary Science 62 159-163... 

In patients with colic, the most relevant clinical sign of hypokalemia is reduced intestinal motility (Geimari 1998, Schaer 1999). However, the association between h) okalemia and ileus in the horse remains undetermined. Other clinical signs include muscle weakness, lethargy and inability to concentrate urine (Schaer 1999). Cardiac conduction abnormalities are rare except in severe hypokalemia and in pre-existing cardiac dysfunction (Gennari 1998). The effect of potassium on acid-base status is small and need not be considered clinically (Corley Marr 1998). 

Furr M 0, Lessard R White N A 1995 Development of a colic severity score for predicting the outcome of equine colic. Veterinary Surgery 24 97-101 Garcia-Lopez J M, Provost P J, Rush J E et al 2001 Prevalence and prognostic importance of hypomagnesemia and hypocalcemia in horses that have colic surgery. American Journal of Veterinary Research 62 7-12... 

Svendsen C K, Hjortkjaer R K, Hesselholt M 1979 Colic in the horse. A clinical and clinical chemical study of 42 cases. Nordisk Veterinaermedicin 31(Suppl) 1-32 Swanson J T, Aldrete J A 1989 Thrombophlebitis after intravenous infusion. Factors affecting its incidence. Rocky Mountain Medical Journal 66 48-51 Tasker J B 1967 Fluid and electrolyte studies in the horse III. Intake and output of water, sodium and potassium in normal horses. Cornell Veterinarian 57 649- 57 Taylor P 1996 Heat stroke, exhaustion and synchronous diaphragmatic flutter (SDF). In Dyson S (ed) A guide to the management of emergencies at equine competitions. Equine Veterinary Journal (A British Equine Veterinary Association Manual), Newmarket, UK, pp. 102-113... 

Reserpine is used in horses as a tranquilizer but its use is not well studied. Toxic effects in horses are extensions of side effects and include colic and drowsiness. Dogs are extremely sensitive to the effects of reserpine. A single 10 mg kg dose can be fatal. 

Cantharidin is an irritant toxic agent present in blister beetles. Only a few of the several species of blister beetles contain cantharidin. Blister beetles are abundant in mid-summer and late summer when alfalfa hay containing the beetles is harvested in the central plains of the United States. Horses are poisoned by eating the alfalfa hay containing crushed swarms of blister beetles. Affected horses develop severe colic. 

Lead poisoning in horses is characterized by neurological effects. Affected horses will be either depressed or excited. Colic and diarrhea are also seen. Because of laryngeal nerve paralysis, horses poisoned by lead also present with difficult respirations and a roaring syndrome. Abortions may also occur. 

---