Veterinary Drug Handbook (VDH) is the reference veterinarians turn to when they want an independent source of information on the drugs that are used in veterinary medicine today.


Dogs: Dog

For susceptible infections:
a) 5.5 - 11 mg/kg PO q6-8h (Aronson and Aucoin 1989)
b) 10 mg/kg (listed as penicillin V) PO q8h (Kirk 1989)

Cats: Cat

For susceptible infections:
a) 5.5 - 11 mg/kg PO q6-8h (Aronson and Aucoin 1989)
b) 10 mg/kg (listed as penicillin V) PO q8h (Kirk 1989)

Horses: Horse

For susceptible infections:
a) 66, 000 U/kg (41.25 mg/kg) PO gives levels greater than 0.1 micrograms/ml for greaterthan 325 minutes which should be effective against Streptococci. (Beech 1987a)(Author's (Plumb) note: Because of the post-antibiotic effect phenomenon; dosingevery 6-8 hours should be sufficient)
b) 110, 000 U/kg (68.75 mg/kg) PO q8h (may yield supra-optimal levels against uncomplicated infections by sensitive organisms). (Schwark et al. 1983)
c) 110, 000 U/kg PO q6-12h (Brumbaugh 1987)
Client Information - Unless otherwise instructed by the veterinarian, this drug should be given onan empty stomach, at least 1 hour before feeding or 2 hours after. Keep oral suspension in therefrigerator and discard any unused suspension after 14 days.
Dosage Forms/Preparations/FDA Approval Status/Withholding Times - Veterinary-Approved Products: None

Human-Approved Products:

Penicillin V Potassium Oral Tablets 125 mg, 250 mg, 500 mg; (Rx)
Penicillin V Potassium Oral Powder for Suspension 125 mg/5 ml in 100 ml, 150 ml and 200 ml, 250 mg/5 ml in 100 ml, 150 ml and 200 ml; (Rx)
There are a multitude of proprietary penicillin VK products, some more widely known include:
V-Cillin K® (Lilly), Pen-Vee K® (Wyeth), Veetids® (Squibb), Uticillin VK® (Upjohn), Beepen-VK® (Beecham), Ledercillin® VK (Lederle)
Chemistry- A synthetic partial opiate agonist, pentazocine is commercially available as two separate salts. The hydrochloride salt, which is found in oral dosage forms, occurs as a white, crystalline powder. It is soluble in water and freely soluble in alcohol. The commercial injection isprepared from pentazocine base with the assistance of lactic acid. This allows the drug to be solublein water. The pH of this product is adjusted to a range of 4-5. Pentazocine is a weak base with anapproximate pKa of 9.0.

Storage, Stability, Compatibility

The tablet preparations should be stored at room temperatureand in tight, light-resistant containers. The injectable product should be kept at room temperature;avoid freezing.
The following agents have been reported to be compatible when mixed with pentazocine lactate:atropine sulfate, benzquinamide HCl, butorphanol tartrate, chlorpromazine HCl, dimenhydrinate, diphenhydramine HCl, droperidol, fentanyl citrate, hydromorphone, hydroxyzine HCl, meperidine
HCl, metoclopramide, morphine sulfate, perphenazine, prochlorperazine edisylate, promazine HCl, promethazine HCl, and scopolamine HBr. The following agents have been reported to beincompatible when mixed with pentazocine lactate: aminophylline, amobarbital sodium, flunixinmeglumine, glycopyrrolate, pentobarbital sodium, phenobarbital sodium, secobarbital sodium, andsodium bicarbonate.


While considered to be a partial opiate agonist, pentazocine exhibits many of thesame characteristics as the true opiate agonists. It is reported to have an analgesic potency ofapproximately one-half that of morphine and five times that of meperidine. It is a very weak antagonist at the mu opioid receptor when compared to naloxone. It will not antagonize the respiratorydepression caused by drugs like morphine, but may induce symptoms of withdrawal in humanpatients dependent to narcotic agents.
Besides its analgesic properties, pentazocine can cause respiratory depression, decreased GImotility, sedation, and it possesses antitussive effects. Pentazocine tends to have less sedativequalities in animals than other opiates and therefore is usually not used as a pre-operative medication.
In dogs, pentazocine has been demonstrated to cause a transient decrease in blood pressure. Inman, pentazocine can cause increases in cardiac output, heart rate, and blood pressure.


Pentazocine is well absorbed following oral, IM, or SQ administration.
Because of a high first-pass effect, only about 1/5th of an oral dose will enter the systemic circulation in patients with normal hepatic function.
After absorption, the drug is distributed widely into tissues. In the equine, it has been shown to be80% bound to plasma proteins. Pentazocine will cross the placenta and neonatal serum levels havebeen measured at 60-65% of maternal levels at delivery. It is not clearly known if or how muchpentazocine crosses into milk.
The drug is primarily metabolized in the liver with resultant excretion by the kidneys of themetabolites. In the horse, approximately 30% of a given dose is excreted as the glucuronide.
Pentazocine and its metabolites have been detected in equine urine for up to 5 days following aninjection. Apparently less than 15% of the drug is excreted by the kidneys in an unchanged form.
Plasma half-lives have been reported for various species: Humans = 2-3 hrs; Ponies = 97 mins.;
Dogs = 22 mins.; Cats = 84 mins.; Swine = 49 mins. Volumes of distribution range from a high of5.09 L/kg in ponies to 2.78 L/kg in cats. In horses, the onset of action has been reported to be 2-3minutes following IV dosing with a peak effect at 5-10 minutes.
Uses, Indications - Pentazocine is labeled for the symptomatic relief of pain of colic in horses andfor the amelioration of pain accompanying postoperative recovery from fractures, trauma, and spinaldisorders in dogs. It has also been used as an analgesic in cats (see adverse effects below) and inswine.
Contraindications/Precautions - All opiates should be used with caution in patients with hypothyroidism, severe renal insufficiency, adrenocortical insufficiency (Addison's), and in geriatricor severely debilitated patients.
Like other opiates, pentazocine must be used with extreme caution in patients with head trauma, increased CSF pressure or other CNS dysfunction (e.g., coma). Pentazocine should not be used inplace of appropriate therapy (medical &/or surgical) for equine colic, but only as adjunctivetreatment for pain.
Because reproductive studies have not been done in dogs, the manufacturer does not recommendits use in pregnant bitches, or bitches intended for breeding. Studies performed in laboratoryanimals have not demonstrated any indications of teratogenicity.
The drug is contraindicated in patients having known hypersensitivity to it.

Adverse Effects, Warnings

In dogs, the most predominant adverse reaction following parenteraladministration is salivation. Other potential side effects at usual doses include fine tremors, emesis, and swelling at the injection site. At very high doses (6 mg/kg) dogs have been noted to developataxia, fine tremors, convulsions, and swelling at the injection site.
Horses may develop transient ataxia, and symptoms of CNS excitement. Pulse and respiratoryrates may be mildly elevated.
The use of pentazocine in cats is controversial. Some clinicians claim that the drug causes dysphoric reactions in cats which precludes its use in this species, while others disagree and state thatdrug may be safely used.
Overdosage - There is little information regarding acute overdose situations with pentazocine. Fororal ingestions, the gut should be emptied if indicated and safe to do so. Symptoms should bemanaged by supportive treatment (O2, pressor agents, IV fluids, mechanical ventilation) andrespiratory depression can be treated with naloxone. Repeated doses of naloxone may be necessary.

Drug Interactions

When used with pentazocine, other CNS depressants (e.g., anestheticagents, antihistamines, phenothiazines, barbiturates, tranquilizers, alcohol, etc.) may cause increased
CNS or respiratory depression; dosage may need to be decreased.

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