The use of particular medications may help to manage or alleviate certain neurobehavioral or movement abnormalities associated with HD. Certain antipsychotic agents, such as haloperidol (Haldol®), a dopamine antagonist, or benzodiazepines, such as clonazepam (Klonopin®), may partially suppress choreic movements and help to control psychiatric abnormalities, including severe agitation, hallucinations, or psychotic delusions. Because antipsychotic therapy may have potentially severe adverse effects, including the development of tardive dyskinesia, such medications should only be used to treat chorea if the condition is functionally disabling. In addition, these agents should be prescribed at the lowest possible dosages and periodically discontinued if possible (drug holidays). Benzodiazepines may also be associated with certain side effects, including fatigue. In addition, benzodiazepines have addictive qualities with long-term use.
Monoamine-depleting agents, such as reserpine or tetrabenazine, may alleviate chorea with a lower risk of causing tardive dyskinesia. However, such agents may aggravate or cause drowsiness, depression, and parkinsonism or have other serious adverse effects (e.g., neuroleptic malignant syndrome, agranulocytosis).
Tetrabenazine (Xenazine®) is approved by the United States Food and Drug Administration (FDA) for the treatment of chorea in HD. Tetrabenazine should be started at a low dose, with a slow dose increase over several weeks to identify the dose that reduces chorea and is well tolerated. Patients who are receiving doses above 50 mg per day should receive a genetic test (called a CYP2D6 test) to determine if they express a gene that allows them to break down (metabolize) tetrabenazine. Those who do not express this gene should not receive more than 50 mg per day of tetrabenazine.
In addition to the potential adverse effects listed above, tetrabenazine can increase the risk of suicidal thoughts or suicide attempts. Patients and families should be aware of this possible effect, and should report it immediately to the patient's physician.
Medical management may also include administration of certain agents to help alleviate depression, anxiety, or obsessive-compulsive behaviors potentially associated with HD. It is important to note that the adverse effects associated with certain medications may be difficult to differentiate from signs of HD. Any medication regimen needs to be assessed on a regular basis to determine the benefits and possible adverse effects of specific therapies and evaluate the need for continued treatment.
Late in the course of the disease, some patients with HD develop signs of parkinsonism. These symptoms typically are not responsive to antiparkinsonism medications, such as levodopa (L-dopa), a precursor of dopamine, or agents that mimic the effects of dopamine (dopamine agonists or amantadine). In most patients, these agents may worsen choreic movements. However, there have been a few reports in which patients with parkinsonism associated with late-onset HD have responded to L-dopa. In addition, the treatment of juvenile HD may include administration of such antiparkinsonian agents.