Phenothiazine Antipsychotic Drug Facts, Side Effects, Dosage

What are phenothiazine antipsychotics?

Phenothiazine antipsychotics are medications used to treat schizophrenia and
manifestations of psychotic disorders. Some phenothiazine antipsychotics, like
prochlorperazine and chlorpromazine, are used for nausea, vomiting, and hiccups.

Although, the exact mechanism of phenothiazine antipsychotics is unknown,
scientists believe that they may work by blocking the action of dopamine in the
brain. Dopamine is a neurotransmitter (chemical) that nerves use to communicate
with one another. Phenothiazine antipsychotics are used when patients do not
respond to other antipsychotics.

What are examples of phenothiazine antipsychotics available in the US?

Examples of phenothiazine antipsychotics are:

• prochlorperazine (Compazine, Compro,
  Procomp),
• chlorpromazine (Promapar, Thorazine),
• fluphenazine (Permitil, Prolixin),
• perphenazine,
• trifluoperazine (Stelazine),
• thioridazine (Mellaril), and
• mesoridazine (no longer available in
  the United States).

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What are the side effects of phenothiazine antipsychotics?

There are many side effects of phenothiazine antipsychotics. Common side
effects include:

• drowsiness,
• dizziness,
• headache,
• low blood pressure, and
• blurred vision.

Phenothiazine antipsychotics may cause extra-pyramidal symptoms such:

• as abnormal muscle contractions,
• difficulty breathing and
  swallowing,
• neck spasms, and
• movement abnormalities on face, arms,
  and legs.

Constipation also is common.

Phenothiazine antipsychotics can also cause neuroleptic malignant syndrome
(NMS), which include symptoms of:

• fever,
• muscle rigidity,
• altered mental status,
• irregular blood pressure, and
• irregular heart rate and rhythm.

All phenothiazine antipsychotics carry a boxed warning of increased deaths in
elderly patients when used for dementia-related psychosis.

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What drugs interact with phenothiazine antipsychotics?

Phenothiazine antipsychotics should not be combined with other antipsychotics
or medications that cause extra-pyramidal side effects and neuroleptic malignant
syndrome due to an increased likelihood of these side effects.

Phenothiazine antipsychotics should be used with caution with medications
(for example, fluoxetine [Prozac, Sarafem, Prozac Weekly]) that reduce the activity of liver enzymes that
eliminate phenothiazines because levels of phenothiazines can increase and lead
to more side effects.

Phenothiazines affect heart rhythm and the risk of abnormal heart rhythms,
especially when they are combined with other drugs that also affect heart
rhythm. Examples include:

• amiodarone (Cordarone),
• fluconazole (Diflucan),
• itraconazole (Sporanox),
• nortriptyline (Pamelor, Aventyl), and
• many other drugs.

What formulations of phenothiazine antipsychotics are available?

• All phenothiazine antipsychotics are
  available in oral tablet form.
• Prochlorperazine also is available as a
  rectal suppository.
• Fluphenazine and mesoridazine are
  available as injections.
• Fluphenazine and mesoridazine are
  available in oral liquid form.

What about taking phenothiazine antipsychotics during pregnancy or while
breastfeeding?

Safe and effective use of phenothiazine antipsychotics during pregnancy has
not been established. Newborns exposed to phenothiazine antipsychotics are at
risk for extrapyramidal and withdrawal symptoms following delivery.
Phenothiazine antipsychotics should only be used if clearly needed when benefits
outweigh potential risks to the fetus.

Phenothiazine antipsychotics may enter breast milk; therefore, they should be
used with caution in women who are
breastfeeding. To avoid potential risks to the
newborn, a decision should be made whether to discontinue the drug or to
discontinue nursing.