Paliperidone (Invega): Antipsychotic Drug Side Effects & Dosage

What is paliperidone, and how does it work (mechanism of action)?

Paliperidone (Invega) is an oral, atypical
antipsychotic used to treat schizophrenia. It is a short acting form of Invega
Sustenna and Invega Trinza. Other atypical antipsychotic drugs include

Atypical antipsychotics differ from typical antipsychotics because they cause
a lesser degree of movement (extrapyramidal) side effects and constipation.

The exact mechanism of action of paliperidone is not known, but, like other
anti-psychotics, it is believed that paliperidone affects the way the brain
works by interfering with communication among the brain's nerves. Nerves
communicate with each other by making and releasing chemicals called
neurotransmitters. The neurotransmitters travel to other nearby nerves where
they attach to receptors on the nerves. The attachment of the neurotransmitters
either stimulates or inhibits the function of the nearby nerves. Paliperidone
blocks several of the receptors on nerves including dopamine type 2, serotonin
type 2, and alpha 2 adrenergic receptors. It is believed that many psychotic
illnesses are caused by abnormal communication among nerves in the brain and
that by altering communication through neurotransmitters, paliperidone can alter
the psychotic state. The FDA approved paliperidone in December, 2006.

What brand names are available for paliperidone?

Invega

Is paliperidone available as a generic drug?

Do I need a prescription for paliperidone?

Yes

What are the side effects of paliperidone?

The most common side effects include

drowsiness,
weight gain,
headache,
upper respiratory tract infection,
increased heart rate,
constipation,
feeling restlessness or difficulty sitting still,
stiffness, and shuffling walk,
tremors, and
slow movements.

Less common but serious side effects include:

Increased risk of stroke and death in elderly
patients with dementia-related psychosis.
Neuroleptic malignant syndrome (NMS): NMS is
a rare but serious side effects associated with the use of antipsychotics. NMS
may result in death and must be treated in the hospital. Signs and symptoms of
NMS may include
- high
  fever,
- sweating (diaphoresis),
- severe muscle stiffness or
  rigidity,
- confusion,
- loss of consciousness,
- high blood pressure,
- rapid
  heartbeat, and
- changes in breathing.
Extrapyramidal side effects (EPS) including:
- Dystonia: painful spasms of the oral,
  throat, or neck muscles that may cause problems with speech, swallowing, and
  stiff neck.
- Akathisia: feelings of restlessness or
  difficulty sitting still.
- Pseudoparkinsonism: drug induced
  Parkinson’s symptoms.
Tardive dyskinesia (TD): Tardive dyskinesia usually occurs
after long-term use of antipsychotics and usually presents with movement
problems affecting the tongue, lips, jaw, face, and extremities.
Metabolic changes including high blood sugar
(hyperglycemia), diabetes mellitus, increase in blood cholesterol, and weight
gain.
HHigh blood levels of prolactin. Prolactin is
a hormone that allows the production of breast milk. High levels of prolactin
may cause menstrual abnormalities, leakage of milk from the breast, development
of breast in males (gynecomastia), and
erection problems in men.
Seizures

QUESTION

Schizophrenia is the most disabling mental illness.
See Answer

What is the dosage for paliperidone?

Paliperidone is administered once daily by mouth.
Tablets should be
swallowed whole and should not be crushed, divided, or chewed.
The starting dose for schizophrenia or schizoaffective disorder in adults is
6 mg daily.
The maintenance dose range is 3 to 12 mg daily.
The maximum dose is
12 mg daily.
The dose for treating schizophrenia in adolescents weighing less than 51 kg
is 3 to 6 mg daily.
The dose for adolescents weighing more than 51 kg is 3 to 12
mg daily.

Which drugs or supplements interact with paliperidone?

Paliperidone can cause low blood pressure especially when standing up from a
sitting or lying position (orthostatic hypotension). Therefore,
paliperidone
should be used cautiously with other drugs also associated with orthostatic
hypotension.

Paliperidone is metabolized (eliminated) by liver enzymes. Drugs that
increase the action of these enzymes will decrease blood levels of paliperidone
thereby decreasing its effect. Paliperidone should not be taken with
carbamazepine (Tegretol), phenytoin (Dilantin), rifampin (Rifadin),
St. John’s Wort, and other drugs that may decrease its blood levels.

Paliperidone blocks the effect of dopamine in the brain while dopamine
agonists such as levodopa (Sinemet) increase the levels of dopamine in the
brain. Combining these agents is not recommended since the effect of both drugs
will be reduced.

Divalproex sodium increases blood levels of paliperidone by 50%. The dose of
paliperidone should be adjusted based on clinical judgment.

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Is paliperidone safe to take if I’m pregnant or breastfeeding?

Unborn babies exposed to antipsychotics during the third trimester
of pregnancy are at risk for extrapyramidal and withdrawal symptoms after birth.
Symptoms reported included agitation, hypertonia, hypotonia, tremor, somnolence,
depressed breathing, and feeding disorder. Currently there is no data on the use
of paliperidone during pregnancy. Paliperidone should only be used during
pregnancy if the potential benefit to the mother outweighs the potential for
side effects in the fetus.

A pregnancy exposure registry has been established to monitor the use of
atypical antipsychotics, including paliperidone, during pregnancy. All pregnant
women treated with atypical antipsychotics are advised to enroll in this
pregnancy registry and report any side effects.

Paliperidone is known to enter human milk but its effects on
the breastfeeding infant or milk production is not yet known.

What else should I know about paliperidone?

What preparations of paliperidone are available?

Tablets: 1.5, 3, 4, 6, and 9 mg

How should I keep paliperidone stored?

Paliperidone should be stored at room temperature, between 15 C and
30 C (59 F and 86 F).