What Factors Affect a Sufficient Aripiprazole Dose?

Aripiprazole, developed by Otsuka Pharmaceutical Company and often sold under the brand name Abilify®, is a member of a class of drugs known as atypical antipsychotics. In addition to its use in the treatment for the symptoms of schizophrenia, it is also sometimes used as a adjunct in the treatment of autism, major depressive disorder, and bipolar disorder. The drug is well-absorbed, requiring no adjustment of the recommended aripiprazole dose when taken with food, nor in cases of decreased liver or kidney function. Elderly patients may use the same dose as other patients, although the recommended dose for children and those using cytochrome P450 3A4 (CYP3A4) or cytochrome P450 2D6 (CYP2D6) inhibiting drugs is much lower. The only other major factor in determining the appropriate dose is the condition to be treated.

When using aripiprazole to treat the symptoms of schizophrenia in adults, a starting dose of 10 to 15 mg per day in generally recommended. Although doses as high as 30 mg may be required to be effective, two weeks should elapse between each dosage increase. The recommended initial dose for children between the ages of 13 and 17 is 2 mg for the first day, increased to a total of 5 mg on the third and fourth days, then finally increased to 10 mg on the seventh and eighth days of treatment. If further dosage adjustments are required, they should be in 5 mg increments, although there is no scientific evidence to support that doses of 30 mg are more effective in children than 10 mg doses.

Aripiprazole alone is not sufficient to adequately treat the symptoms of bipolar disorder; however, some studies have suggested that it may help reduce symptoms when incorporated into an existing therapeutic regimen. Both the recommended starting and targeted aripiprazole dose in adults is 15 mg taken once a day in addition to valproate or lithium, although it can be increased as high as 30 mg daily. Children between the ages of 10 and 17 should use a much lower starting dose of 2 mg daily, increasing to 5 mg after the first two days and then 10 mg in two more days. Any further dose increases should not exceed 30 mg per day, with increases of no more than 5 mg per day.

As with the treatment of bipolar disorder, aripiprazole should be used as a complement to existing treatment, rather than the primary treatment for major depressive disorder. The standard aripiprazole dose used in the depression in adults is 2 to 5 mg daily in addition to existing medication. Dose increases, if needed, should be incorporated at rates no faster than once per week and should not be greater than 5 mg. An effective dose for this purpose should be between 2 to 15 mg daily. Aripiprazole has not been approved for the treatment of depression in children.

Some of the medications used in the treatment of depression may be CYP2D6 inhibitors, necessitating a reduction in the starting dose of aripiprazole. Drug interactions with prescription anti-fungal medications are also a concern, as many of these are also CYP3A4 inhibitors. Due to their effects on the liver enzymes responsible for breaking down aripiprazole, the dosage for patients using these medications should be reduced by half. CYP3A4 inducing drugs, however, require that the usual aripiprazole dose be doubled during the course of treatment, then reduced to 10 to 15 mg after the cessation of therapy. If available, medications that do not affect liver enzyme levels should be prescribed instead.

Since increasing the dose of the medication may increase the incidence or intensity of side-effects, most physicians will choose to use a low initial dose, increasing it slowly to determine what the lowest possible sufficient aripiprazole dose may be. The full effects of a dosage adjustment may not be felt for at least two weeks afterward. For this reason, it is important to wait until then before increasing the aripiprazole dose again. If taking this medication produces symptoms like weakness, drowsiness, pupil dilation, altered heart rate, nausea, vomiting, confusion or uncontrollable body movements, the aripiprazole dose should be lowered considerably, as these are symptoms of overdose. More severe symptoms include loss of consciousness, seizures or coma.