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.

PROPOFOL

Chemistry - Propofol is an alkylphenol derivative (2, 6 - diisopropylphenol). The commerciallyavailable injection is an emulsion containing 100 mg/ml of soybean oil, 22.5 mg/ml of glycerol, and12 mg/ml of egg lecithin. The emulsion has a pH of 7-8.5. Propofol may also be known asdisoprofol.

Storage, Stability, Compatibility

Store propofol injection below 22°C (72°F), but not below4°C (40°F.); do not refrigerate or freeze. Protect from light. Shake well before using. Do not use ifthe emulsion has separated. The manufacturer recommends discarding any unused portion at theend of the anesthetic procedure or after 6 hours, whichever occurs sooner.
Compatibility with other agents has not been well established. Propofol is compatible with thecommonly used IV solutions (e.g., LRS, D5W) when injected into a running IV line.

Pharmacology - PROPOFOL

Propofol is a short acting hypnotic unrelated to other general anesthetic agents.
Its mechanism of action is not well understood.
In dogs, propofol produces rapid, yet smooth and excitement-free anesthesia induction (in 30-60seconds) when given slowly IV. Sub-anesthetic dosages will produce sedation, restraint and anunawareness of surroundings. Anesthetic dosages produces unconsciousness.
Propofol's cardiovascular effects include arterial hypotension, bradycardia, (especially in combination with opiate premedicants) and negative inotropism. It causes significant respiratory depression, particularly with rapid administration or very high dosages. Propofol also decreases intraocular pressure, increases appetite and has antiemetic properties. It does not appear to precipitatemalignant hyperthermia and it has little or no analgesic properties.

Uses, Indications

In appropriate patients, propofol may be useful as an induction agent(especially before endotracheal intubation or an inhalant anesthetic); as an anesthetic for outpatientdiagnostic or minor procedures (e.g., laceration repair, radiologic procedures, minor dentistry, minor biopsies, endoscopy, etc.). Propofol may be of particular usefulness for use in Greyhoundsand in patients with preexisting cardiac dysrhythmias.
In dogs, propofol's labeled indications are: 1) for induction of anesthesia; 2) for maintenance ofanesthesia for up to 20 minutes; 3) for induction of general anesthesia where maintenance isprovided inhalant anesthetics.

Pharmacokinetics - PROPOFOL

After IV administration, propofol rapidly crosses the blood brain barrier andhas an onset of action usually within one minute. Duration of action after a single bolus lasts about2-5 minutes. It is highly bound to plasma proteins (95-99%), crosses the placenta, is highlylipophilic and reportedly enters maternal milk.
Propofol's short duration of action is principally due to its rapid redistribution from the CNS toother tissues. It is rapidly biotransformed in the liver via glucuronide conjugation to inactivemetabolites which are then excreted primarily by the kidneys. Because cat's do not glucuronidate aswell as dogs or humans, this may help explain their problems with consecutive day administration(see Adverse Effects below).
There are limited data available on propofol's pharmacokinetic parameters in dogs. The steadystate volume of distribution is >3L/kg, elimination half life is about 1.4 hours and clearance is about50 ml/kg/min.

Contraindications, Precautions, Reproductive Safety

Propofol is contraindicated in patientshypersensitive to it or any of component of the product. It should not be used in patients wheregeneral anesthesia or sedation are contraindicated. Propofol should only be used in facilities wheresufficient monitoring and patient-support capabilities are available.
Because patients who are in shock, under severe stress or have undergone trauma may be overlysensitive to the cardiovascular and respiratory depressant effects of propofol, it should be used withcaution in these patients. Adequate perfusion should be maintained before and during propofolanesthesia and dosage adjustments may be necessary.
Because propofol is so highly bound to plasma proteins, patients with hypoproteinemia may besusceptible to untoward effects. Other general anesthetic agents may be a safer choice in thesepatients.
The benefits of propofol should be weighed against its risks in patients with a history of hyperlipidemia, seizures or anaphylactic reactions. Cat's with preexisting liver disease may be susceptibleto longer recovery times.
Propofol crosses the placenta and its safe use during pregnancy has not been established. Highdosages (6 times those recommended) in laboratory animals caused increased maternal death anddecreased offspring survival rates after birth.

Adverse Effects, Warnings

Because there is a high incidence of apnea with resultant cyanosis ifpropofol is given too rapidly, it should be given slowly (25% of the calculated dose every 30seconds until desired effect).
Propofol has been documented to cause histamine release in some patients and anaphylactoidreactions (rare) have been noted in humans. Propofol has direct myocardial depressant propertiesand resultant arterial hypotension has been reported.
Occasionally, dogs may exhibit seizure-like symptoms (paddling, opisthotonus, myoclonictwitching) during induction, which if persist, may be treated with intravenous diazepam. Propofolmay have both anticonvulsant and seizure-causing properties. It should be used with caution inpatients with a history of, or active seizure disorders. However, some clinicians believe that propofolis actually better-suited to use in seizure patients or in high seizure-risk procedures (e.g., myelography) than is thiopental.
While propofol is not inexpensive, it should be used in a single-use fashion as it is a good growthmedium (contains no preservative) for bacteria.
When used repeatedly (once daily) in cats, increased Heinz body production, slowed recoveries, anorexia, lethargy, malaise, and diarrhea have been noted. Heinz body formation is due to oxidativeinjury to RBC's and has been documented in cats with other phenolic compounds as well.
Consecutive use in dogs appears to be safe.
Pain upon injection has been reported in humans, but does not appear to be of major significancefor dogs or cats. Extravasation of injection is not irritating nor does it cause tissue sloughing.

Overdosage, Acute Toxicity

Overdosages are likely to cause significant respiratory depressionand potentially cardiovascular depression. Treatment should consist of propofol discontinuation, artificial ventilation with oxygen, and if necessary, symptomatic and supportive treatment forcardiovascular depression (e.g., intravenous fluids, pressors, anticholinergics, etc.).

Drug Interactions

Propofol used in conjunction with preanesthetic agents (e.g., acepromazine, opiates) may cause increased vasodilation and negative cardiac inotropy. This may be ofparticular concern in animals with preexisting cardiopulmonary disease, in shock, or suffering fromtrauma.
Propofol-induced bradycardia may be exacerbated in animals receiving opiate premedicants, particularly when anticholinergic agents (e.g., atropine) are not given concurrently.
As would be logically expected, increased CNS depressant effects and recovery times may benoted in patients receiving other CNS depressant medications with propofol.
Drugs that inhibit the hepatic P-450 enzyme system (e.g., chloramphenicol, cimetidine)or other basic lipophilic drugs (e.g., fentanyl, halothane) may potentially increase therecovery times associated with propofol. Clinical significance is unclear, but in cats it may be ofsignificance.

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