It is approved by the U.S. Food and Drug Administration to treat psychiatric disorders such as schizophrenia. It may also be prescribed off-label to treat some symptoms of Huntington’s disease, such as chorea.
How Abilify works
Antipsychotic medications generally block the transmission of signals in the brain that may be overactive in certain conditions. Abilify is an atypical antipsychotic medication: It acts as both a partial antagonist, blocking the transmission of certain signals, and a partial agonist increasing the frequency of others.
Nerve signals are transmitted between nerve cells by chemical messengers called neurotransmitters. These bind to and activate specific receptors found on nerve cells. Dopamine is one such neurotransmitter that has several roles, including the control of mood and movement.
In Huntington’s disease, changes in the brain may cause the dopamine system to be overactive. This may result in chorea or involuntary movements.
Abilify is a “dopamine stabilizer,” meaning it can act as a dopamine receptor antagonist when the dopamine system is overactive, and a partial agonist when dopamine levels are low. It is able to do this because it has a very high affinity for dopamine receptors, so it binds to the receptor in place of dopamine. Abilify still activates the receptor but does so at a much weaker level than dopamine itself would. Ultimately, this should reduce the overactivation of the dopamine system and reduce chorea.
Abilify also acts on other neurotransmitter receptors, such as serotonin (5-HT) receptors and either partially works as an agonist on the 5-HT1A receptor, or an antagonist on the 5-HT2A receptor.
Abilify in clinical trials
While there have been no large-scale, randomized, controlled trials investigating Abilify in Huntington’s disease, there are several published case studies demonstrating a benefit in patients with the disease.
A case study published in the American Journal of Psychiatry showed that a single male patient with Huntington’s disease had significant improvements in his symptoms of psychosis and chorea after only two weeks of treatment with Abilify. Prior to the treatment, the patient scored an 18 on the unified Huntington’s disease rating scale (UHDRS) for chorea, which was reduced to 8 after beginning Abilify treatment. His behavioral symptoms such as aggression were also reduced.
A second case study series published in the journal Neuropsychiatric Disease and Treatment described the effects of Abilify taken for one year by three Huntington’s disease patients. The results suggested that Abilify markedly improved behavioral, mood, and motor symptoms, including chorea. No severe adverse events were reported. The researchers noted that the treatment may have less of a risk of metabolic dysfunction leading to weight gain than similar therapies such as Zyprexa (olanzapine).
A small trial carried out in six patients compared the effects of Abilify with those of Xenazine (tetrabenazine) as a therapy for Huntington’s chorea. Patients were randomly assigned to receive one of the two therapies for three months, then switched therapies for another three months. The results, published in the scientific journal Movement Disorders, confirmed that both treatments successfully improved chorea. Abilify potentially had fewer side effects, causing less sedation and sleepiness, than Xenazine.
A fourth case study published in the Journal of Neuropsychiatry and Clinical Neurosciences described how treatment with Abilify significantly improved both motor and psychotic symptoms caused by Huntington’s disease in a 55-year-old male patient. Behavioral, psychotic, and chorea symptoms all showed a marked improvement after a month of treatment, improvements that were sustained at a 16-month follow-up while still on Abilify.
Common side effects of Ability include difficulty speaking, drooling, reduced balance, akathisia (restless legs syndrome), shuffling walk, stiffness, dystonia (muscle spasms or contractions), and dyskinesia (involuntary movements).
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