APOMORPHINE HCL

Chemistry - A centrally-acting emetic, apomorphine occurs as a white powder or minute, white orgrayish-white crystals and is sparingly soluble in water or alcohol.

Storage, Stability, Compatibility

Apomorphine soluble tablets should be stored in tight containers at room temperature (15-30°C) and be protected from light.
Upon exposure to light and air, apomorphine gradually darkens in color. Discolored tabletsshould not be used. Apomorphine solutions are more stable in acidic than alkaline solutions. A0.3% solution of apomorphine has a pH of about 3-4.
Solutions of apomorphine can be made by solubolizing tablets in at least 1 - 2 ml of either sterilewater for injection or 0.9% sodium chloride for injection. After being sterilized by filtration, thesolution is stable for 2 days if protected from light and air and stored in the refrigerator. Do not usesolutions that are discolored or form a precipitate after filtering.

Pharmacology - APOMORPHINE HCL

Apomorphine stimulates dopamine receptors in the chemoreceptor trigger zone, thus inducing vomiting. It can cause both CNS depression and stimulation, but tends to cause morestimulatory effects. Medullary centers can be depressed with resultant respiratory depression.

Uses, Indications

Apomorphine is used primarily as an emetic in dogs, and is considered to bethe emetic of choice in dogs by many clinicians.

Pharmacokinetics - APOMORPHINE HCL

Apomorphine is slowly absorbed after oral administration and has unpredictable efficacy when given by this route and, therefore, is usually administered parenterally or topically to the eye. When given intravenously in dogs, emesis occurs very rapidly; after IM use, vomiting occurs generally within 5 minutes but may be more prolonged. Topical administration to the conjunctival sac is usually effective, but less so than either IV or IM administration.
Apomorphine is primarily conjugated in the liver and then excreted in the urine.

Contraindications, Precautions, Reproductive Safety

Emetics can be an important aspect inthe treatment of orally ingested toxins, but must not be used injudiciously. Emetics should not beused in rodents or rabbits, because they are either unable to vomit or do not have stomach wallsstrong enough to tolerate the act of emesis. Emetics are also contraindicated in patients that are:hypoxic, dyspneic, in shock, lack normal pharyngeal reflexes, seizuring, comatose, severely CNSdepressed or where CNS function is deteriorating, or extremely physically weak. Emetics shouldalso be withheld in patients who have previously vomited repeatedly. Emetics are contraindicated inpatients who have ingested strong acids, alkalies, other caustic agents because of the risks ofadditional esophogeal or gastric injury with emesis. Because of the risks of aspiration, emetics areusually contraindicated after petroleum distillate ingestion, but may be employed when the risks oftoxicity of the compound are greater than the risks of aspiration. Use of emetics after ingestion ofstrychnine or other CNS stimulants may precipitate seizures.
Emetics generally do not remove more than 80% of the material in the stomach (usually 40-60%)and successful induction of emesis does not signal the end of appropriate monitoring or therapy. Inaddition to the contraindications outlined in the general statement, apomorphine should not be usedin cases of oral opiate or other CNS depressant (e.g., barbiturates) toxicity, or in patientshypersensitive to morphine.
The use of apomorphine in cats is controversial, and several clinicians state that it should not beused in this species as it is much less effective than either xylazine or ipecac syrup and possiblyless safe.
If vomiting does not occur within the expected time after apomorphine administration, repeateddoses are also unlikely to induce emesis and may cause symptoms of toxicity.
The reproductive safety of this drug has not been established; weigh the risks of use versus thepotential benefits.

Adverse Effects, Warnings

At usual doses, the principal adverse effect that may be seen withapomorphine, is protracted vomiting. Protracted vomiting after ophthalmic administration may beaverted by washing the conjunctival sac with sterile saline or ophthalmic rinsing solution.
Excitement, restlessness, CNS depression or respiratory depression are usually only associatedwith overdoses of the drug.

Overdosage, Acute Toxicity

Excessive doses of apomorphine may result in respiratory and/orcardiac depression, CNS stimulation (excitement, seizures) or depression and protracted vomiting.
Naloxone may reverse the CNS and respiratory effects of the drug, but cannot be expected to haltthe vomiting. Atropine has been suggested to treat severe bradycardias.

Drug Interactions

Antiemetic drugs, particularly antidopaminergic drugs (e.g., phenothiazines) may negate the emetic effects of apomorphine.
Additive CNS, or respiratory depression may occur when apomorphine is used with opiates orother CNS or respiratory depressants (e.g., barbiturates).