Perphenazine is a phenothiazine antipsychotic used to treat serious mental disorders. It has also been used to treat severe nausea and vomiting. It is sold in the United States under the brand name Trilafon and is also available under its generic name.


Perphenazine is used to treat psychotic disorders and severe nausea and vomiting.


Perphenazine is one of many drugs in the class called phenothiazine derivatives. Phenothiazines work by inhibiting the actions of the brain chemicals, dopamine and norepinephrine, which are overproduced in individuals with psychosis .

Recommended dosage

For the treatment of psychosis, adults usually receive a total of 4 mg to 16 mg taken as tablets in three or four doses daily, up to a maximum of 64 mg each day. Injections of perphenazine are also available and are typically given in 5 mg doses every six hours, up to 15 mg per day. Hospitalized patients can receive up to 30 mg per day in the injectable form of perphenazine.

Adult patients with serious nausea and vomiting receive 8 mg to 16 mg per day as tablets in divided into several doses up to a maximum of 24 mg per day. Injections are typically given in 5 mg to 10 mg doses every six hours, up to 15 mg per day in patients who are not confined to bed. Hospitalized patients can receive up to a maximum of 30 mg per day. Intravenous perphenazine can be given to nausea and vomiting patients up to 1 mg every one to two minutes to a maximum of 5 mg.

The correct dosage of perphenazine must be carefully determined for each patient. Physicians try to find a dose that controls symptoms of the disease without causing intolerable side effects. Dosage guidelines for the treatment of psychosis have not been established for children under the age of 12 years. In children over age 12, the lowest adult dosage is generally used to treat psychosis. Children with severe nausea and vomiting are usually given 5 mg injections every six hours.


Persons who take perphenazine should not stop taking the drug abruptly. Instead, the dose should be decreased gradually, then stopped. People who take perphenazine often have develop sunburn more easily than Sunscreen should be used by people, especially fair-skinned individuals, taking perphenazine.

People who are known to have severe central nervous system depression should not take perphenazine or any other drug in its class. In addition, those with a prior history of brain damage, coma, or bone marrow depression should not receive perphenazine without a thorough evaluation by a doctor.

Children under the age of 12 years, the elderly (over age 65), those with a history of epilepsy, glaucoma, prostate problems, severe asthma, and other severe breathing problems should receive perphenazine only with great caution and under close supervision of a physician. In addition, persons with a history of heart or blood vessel disease and those with a history of liver or kidney disease should take perphenazine only after a thorough evaluation. Perphenazine should also be used cautiously when taken over a long period. Rarely should perphenazine be taken by pregnant or nursing women.

Side effects

Serious or life-threatening side effects due to perphenazine are rare. However, if any of these occur, patients should contact their doctors or get immediate medical attention: seizures , irregular heartbeat, significant changes in blood pressure, muscle stiffness, weakness, pale skin color, and increased sweating. The treating doctor should be contacted immediately if any of these common side effects develop: rapid movements of the tongue, uncontrolled chewing movement, unusual amounts of lip smacking, and frequent movement of the arms or legs. The treating doctor should be contacted relatively soon if any of the following common side effects develop: reduced balance control, muscle spasms, restlessness, trembling, weakness in the limbs, blurred vision, and decreased night vision.

Less common side effects that need to be reported to the doctor include severe sunburn, skin rashes, and urination problems. Rare side effects that should be reported to the doctor include abdominal pain, muscle aches, joint aches, fever, chills, muscle weakness, and vomiting. Common and not serious side effects include constipation, drowsiness, decreased sweating, mouth dryness, and nasal congestion. Uncommon and not typically serious side effects include decreased sexual desire, increased susceptibility to sunburn, menstrual cycle changes, swelling or pain in the breasts, and weight gain.


Combining perphenazine with drugs such as the anti-mallarials amodiaquine, chloroquine, and sulfadoxine-pyrimethamine (Fansidar) can increase the concentrations within the body of these three latter drugs.

Perphenazine combined with barbiturates tends to lower the concentrations of perphenazine in the body. Combining perphenazine with clonidine (Catapres), guanadrel (Hylorel), and guanethidine (Ismelin) can produce dangerously low blood pressure.

Perphenazine should not be combined with alcohol, because alcohol increases the drug's depressive effect on the central nervous system. Perphenazine inhibits the effects of levodopa in Parkinson patients when the two are combined. Lithium combined with perphenazine lowers the levels of both drugs.

Perphenazine should not be combined with analgesics (pain killers) containing narcotics because of the combination increases depressive effects on the central nervous system. Orphenadrine (Norflex) combined with perphenazine can reduce the beneficial effects of perphenazine.



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Mark Mitchell, M.D.

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