NADA No.: 140-442
NDC No.: 50989-234-11

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Active Ingredients:

Each mL contains:
Xylazine hydrochloride equivalent to base activity 100 mg
Methylparaben 0.9 mg
Propylparaben 0.1 mg
Sodium citrate dihydrate 0.5 mg
Water for injection. The pH is adjusted with citric acid and sodium citrate.


Xylazine should be used in horses when it is desirable to produce a state of sedation accompanied by a shorter period of analgesia. Xylazine has been used successfully as follows:

1. Diagnostic procedures, such as oral and ophthalmic examinations, abdominal palpation, rectal palpation, vaginal examination, catheterization of the bladder and radiographic examinations.

2. Orthopedic procedures, such as the application of casting materials and splints.

3. Dental procedures.

4. Minor surgical procedures of short duration, such as debridement, removal of cutaneous neoplasms and suturing of lacerations.

5. To calm and facilitate the handling of fractious animals.

6. Major surgical procedures:

    a. When used as a pre-anesthetic to general anesthesia.
    b. When used in conjunction with local anesthetics.


Xylazine, a non-narcotic compound, is a sedative and analgesic as well as a muscle relaxant. Its sedative and analgesic activity is related to central nervous system depression. Its muscle-relaxant effect is based upon inhibition of the intraneural transmission of impulses in the central nervous system. The principal pharmacological activities develop within 10 to 15 minutes after intramuscular injection, and within three to five minutes following intravenous administration. A sleeplike state, the depth of which is dose-dependent, is usually maintained for one to two hours, while analgesia lasts from 15 to 30 minutes. The muscle-relaxant effect causes relaxation of the skeletal musculature complementing sedation and analgesia. In animals under the influence of xylazine, the respiratory rate is reduced as in natural sleep. Following treatment with xylazine, the heart rate is decreased and a transient change in the conductivity of the cardiac muscle may occur, as evidenced by a partial atrioventricular block. This resembles the atrioventricular block often observed in normal horses.1,2,3,4 Although a partial A-V block may occasionally occur following the intramuscular injection of xylazine, the incidence is less than when it is administered intravenously. Intravenous administration of xylazine causes a transient rise in blood pressure, followed by a slight decrease. Xylazine does not have an effect on blood clotting time or on other hematologic parameters.

Dosage and Administration:

1. Dosage:
Intravenous - 0.5 mL/100 lbs. of body weight (0.5 mg/lb., or 1.1 mg/kg).
Intramuscular - 1.0 mL/100 lbs. of body weight (1 mg/lb., or 2.2 mg/kg).
Following the injection of xylazine, the animal should be allowed to rest quietly until the full effect has been reached. These dosages produce sedation which is usually maintained for one (1) to two (2) hours, and analgesia which lasts for 15 to 30 minutes.

2. Pre-anesthetic to local anesthesia: Xylazine at the recommended dosages can be used in conjunction with local anesthetics, such as procaine or lidocaine.

3. Pre-anesthetic to general anesthesia: Xylazine, at the recommended dosage rates, produces an additive effect to central nervous system depressants such as pentobarbital sodium, thiopental sodium and thiamylal sodium. Therefore, the dosage of such compounds should be reduced and administered to the desired effect. In general, only one-third ( 1 §3) to one-half ( 1/2) of the calculated dosage of the barbiturates will be needed to produce a surgical plane of anesthesia. Postanesthetic or emergence excitement has not been observed in animals pre-anesthetized with xylazine. Xylazine has been used successfully as a pre-anesthetic agent for pentobarbital sodium, thiopental sodium, thiamylal sodium, nitrous oxide, ether, halothane, glyceryl guaiacolate and methoxyflurane anesthesia.


Protect from heat. Do not store at temperatures over 30°C (86°F).


Federal law restricts this drug to use by or on the order of a licensed veterinarian. Careful consideration should be given before administering to horses with significantly depressed respiration, severe pathologic heart disease, advanced liver or kidney disease, severe endotoxic or traumatic shock and stress conditions such as extreme heat, cold, high altitude or fatigue. Do not use xylazine in conjunction with tranquilizers. Since an additive effect results from the use of xylazine with the barbiturate compounds, it should be used with caution with these central nervous system depressants. Products known to produce respiratory depression or apnea, such as thiamylal sodium, should be given at a reduced dosage and, when injected intravenously, should be administered slowly. When intravenous administration is desired, avoid perivascular injection in order to achieve the desired effect. Studies have shown negligible evidence of tissue irritation following perivascular injection of xylazine. Intracarotid arterial injection should be avoided. As with many compounds, including tranquilizers, immediate violent seizures followed by collapse may result from inadvertent administration into the carotid artery. Although the reaction with xylazine is usually transient and recovery may be rapid and complete, special care should be taken to assure that the needle is in the jugular vein rather than the carotid artery. Bradycardia and an arrhythmia in the form of incomplete atrioventricular block have been reported following xylazine administration. Although clinically the importance of this effect is questioned, 1,2,3,4 a standard dose of atropine given prior to or following xylazine injection will greatly decrease the incidence. The analgesic effect is variable, and depth should be carefully assayed prior to surgical/clinical procedures. Variability of analgesia occurs most frequently at the distal extremities of the horse. In spite of sedation, the practitioner and handlers should proceed with caution since defense reactions may not be diminished. Sedation for transport is most successful if actual transportation is begun after the full effect of the drug has been reached and the animal’s stability is maintained while standing. In addition, it should be noted that animals under the influence of xylazine can be aroused by noise or other stimuli and this may increase the risk of injury.


Not for human use. The drug is for use in horses only and should not be administered to food-producing animals.


Xylazine has been tested in horses at five times the recommended dose. Doses of this magnitude may produce convulsions and long periods of sedation. Side Effects: Xylazine used at the recommended dosage levels may occasionally cause slight muscle tremors, bradycardia with partial A-V heart block and a reduced respiratory rate. Movement in response to sharp auditory stimuli may be observed. Sweating, rarely profuse, has been reported following administration.


Available upon request.


50 mL vials.

VEDCO - 11/10/98.1