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

• olanzapine (Zyprexa),
• quetiapine (Seroquel),
• ziprasidone (Geodon), and
• aripiprazole (Abilify).

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.

Invega

GENERIC AVAILABLE: No

Yes

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

• 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.

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.

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 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).