29.12 Calcium Channel Blockers
957
Precautions and Adverse Reactions
Buspirone does not cause weight gain, sexual dysfunction, dis-
continuation symptoms, or significant sleep disturbance. It does
not produce sedation or cognitive and psychomotor impairment.
The most common adverse effects of buspirone are headache,
nausea, dizziness, and (rarely) insomnia. No sedation is associ-
ated with buspirone. Some persons may report a minor feeling
of restlessness, although that symptom may reflect an incom-
pletely treated anxiety disorder. No deaths have been reported
from overdoses of buspirone, and the median lethal dose is
estimated to be 160 to 550 times the recommended daily dose.
Buspirone should be used with caution by persons with hepatic
and renal impairment, pregnant women, and nursing mothers.
Buspirone can be used safely by the elderly.
Drug Interactions
The coadministration of buspirone and haloperidol (Haldol)
results in increased blood concentrations of haloperidol. Bus-
pirone should not be used with MAOIs to avoid hypertensive
episodes, and a 2-week washout period should pass between
the discontinuation of MAOI use and the initiation of treatment
with buspirone. Drugs or foods that inhibit CYP3A4, for exam-
ple, erythromycin (E-mycin), itraconazole (Sporanox), nefazo-
done (Serzone), and grapefruit juice, increase buspirone plasma
concentrations.
Laboratory Interferences
Single doses of buspirone can cause transient elevations
in growth hormone, prolactin, and cortisol concentrations,
although the effects are not clinically significant.
Dosage and Clinical Guidelines
Buspirone is available in single-scored 5- and 10-mg tablets and
triple-scored 15- and 30-mg tablets; treatment is usually initi-
ated with either 5 mg orally three times daily or 7.5 mg orally
twice daily. The dosage can be raised 5 mg every 2 to 4 days to
the usual dosage range of 15 to 60 mg a day.
Buspirone should not be used in patients with past hypersen-
sitivity to buspirone, in cases of diabetes-associated metabolic
acidosis, or in patients with severely compromised liver or renal
function.
Switching from a Benzodiazepine to Buspirone
Buspirone is not cross-tolerant with benzodiazepines, barbi-
turates, or alcohol. A common clinical problem, therefore, is
how to initiate buspirone therapy in a person who is currently
taking benzodiazepines. There are two alternatives. First, the
clinician can start buspirone treatment gradually while the
benzodiazepine is being withdrawn. Second, the clinician can
start buspirone treatment and bring the person up to a thera-
peutic dosage for 2 to 3 weeks while the person is still receiv-
ing the regular dosage of the benzodiazepine and then slowly
taper the benzodiazepine dosage. Patients who have received
benzodiazepines in the past, especially in recent months, may
find that buspirone is not as effective as the benzodiazepines in
the treatment of their anxiety. This might be explained by the
absence of the immediate mildly euphoric and sedative effects
of the benzodiazepines. The coadministration of buspirone and
benzodiazepines may be effective in the treatment of persons
with anxiety disorders who have not responded to treatment
with either drug alone.
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▲▲
29.12 Calcium Channel
Blockers
The intracellular calcium ion regulates activity of multiple neu-
rotransmitters such as serotonin and dopamine, and that action
may account for its role as a treatment in mood disorders. Cal-
cium channel inhibitors are used in psychiatry as antimanic
agents for persons who are refractory to or cannot tolerate treat-
ment with first-line mood-stabilizing agents such as lithium
(Eskalith), carbamazepine (Tegretol), and divalproex (Depak-
ote). Calcium channel inhibitors include nifedipine (Procardia,
Adalat), nimodipine (Nimotop), isradipine (DynaCirc), amlo-
dipine (Norvasc, Lotrel), nicardipine (Cardene), nisoldipine
(Sular), nitrendipine, and verapamil (Calan). They are used for
control of mania and ultradian bipolar disorder (mood cycling
in less than 24 hours).
The results of a large genetic study have rekindled interest in
the potential clinical uses of calcium channel blockers (CCBs).
Two genome-wide findings implicated genes encoding L-type
voltage-gated calcium channel subunits as susceptibility genes
for bipolar disorder, schizophrenia, major depressive disorder,
ADHD, and autism.
