Dependence and Withdrawal Reactions, Including
Seizures
Certain adverse clinical events, some life-threatening, are a
direct consequence of physical dependence to alprazolam. These include a
spectrum of withdrawal symptoms; the most important is seizure (see DRUG ABUSE AND DEPENDENCE). Even
after relatively short-term use at the doses recommended for the treatment of
transient anxiety and anxiety disorder (i.e., 0.75 to 4 mg per day), there is
some risk of dependence. Spontaneous reporting system data suggest that the risk
of dependence and its severity appear to be greater in patients treated with
doses greater than 4 mg/day and for long periods (more than 12 weeks). However,
in a controlled postmarketing discontinuation study of panic disorder patients,
the duration of treatment (3 months compared to 6 months) had no effect on the
ability of patients to taper to zero dose. In contrast, patients treated with
doses of alprazolam greater than 4 mg/day had more difficulty tapering to zero
dose than those treated with less than 4 mg/day.
The importance of dose and the risks of alprazolam as
a treatment for panic disorder
Because the management of panic disorder often requires the use
of average daily doses of alprazolam above 4 mg, the risk of dependence among
panic disorder patients may be higher than that among those treated for less
severe anxiety. Experience in randomized placebo-controlled discontinuation
studies of patients with panic disorder showed a high rate of rebound and
withdrawal symptoms in patients treated with alprazolam compared to
placebo-treated patients.
Relapse or return of illness was defined as a return of symptoms
characteristic of panic disorder (primarily panic attacks) to levels
approximately equal to those seen at baseline before active treatment was
initiated. Rebound refers to a return of symptoms of panic disorder to a level
substantially greater in frequency, or more severe in intensity than seen at
baseline. Withdrawal symptoms were identified as those which were generally not
characteristic of panic disorder and which occurred for the first time more
frequently during discontinuation than at baseline.
In a controlled clinical trial in which 63 patients were randomized to
alprazolam and where withdrawal symptoms were specifically sought, the following
were identified as symptoms of withdrawal: heightened sensory perception,
impaired concentration, dysosmia, clouded sensorium, paresthesias, muscle
cramps, muscle twitch, diarrhea, blurred vision, appetite decrease, and weight
loss. Other symptoms, such as anxiety and insomnia, were frequently seen during
discontinuation, but it could not be determined if they were due to return of
illness, rebound, or withdrawal.
In two controlled trials of 6 to 8 weeks duration where the ability of
patients to discontinue medication was measured, 71% to 93% of patients treated
with alprazolam tapered completely off therapy compared to 89% to 96% of
placebo-treated patients. In a controlled postmarketing discontinuation study of
panic disorder patients, the duration of treatment (3 months compared to 6
months) had no effect on the ability of patients to taper to zero dose.
Seizures attributable to alprazolam were seen after drug discontinuance or
dose reduction in 8 of 1980 patients with panic disorder or in patients
participating in clinical trials where doses of alprazolam greater than 4 mg/day
for over 3 months were permitted. Five of these cases clearly occurred during
abrupt dose reduction, or discontinuation from daily doses of 2 to 10 mg. Three
cases occurred in situations where there was not a clear relationship to abrupt
dose reduction or discontinuation. In one instance, seizure occurred after
discontinuation from a single dose of 1 mg after tapering at a rate of 1 mg
every 3 days from 6 mg daily. In two other instances, the relationship to taper
is indeterminate; in both of these cases the patients had been receiving doses
of 3 mg daily prior to seizure. The duration of use in the above 8 cases ranged
from 4 to 22 weeks. There have been occasional voluntary reports of patients
developing seizures while apparently tapering gradually from alprazolam. The
risk of seizure seems to be greatest 24 to 72 hours after discontinuation (see
DOSAGE AND ADMINISTRATION for
recommended tapering and discontinuation schedule).
Status Epilepticus and Its Treatment
The medical event voluntary reporting system shows that
withdrawal seizures have been reported in association with the discontinuation
of alprazolam. In most cases, only a single seizure was reported; however,
multiple seizures and status epilepticus were reported as well.
Interdose Symptoms
Early morning anxiety and emergence of anxiety symptoms between
doses of alprazolam have been reported in patients with panic disorder taking
prescribed maintenance doses of alprazolam. These symptoms may reflect the
development of tolerance or a time interval between doses which is longer than
the duration of clinical action of the administered dose. In either case, it is
presumed that the prescribed dose is not sufficient to maintain plasma levels
above those needed to prevent relapse, rebound or withdrawal symptoms over the
entire course of the interdosing interval. In these situations, it is
recommended that the same total daily dose be given divided as more frequent
administrations (see DOSAGE AND
ADMINISTRATION).
Risk of Dose Reduction
Withdrawal reactions may occur when dosage reduction occurs for
any reason. This includes purposeful tapering, but also inadvertent reduction of
dose (e.g., the patient forgets, the patient is admitted to a hospital).
Therefore, the dosage of alprazolam should be reduced or discontinued gradually
(see DOSAGE AND
ADMINISTRATION).
CNS Depression and Impaired Performance
Because of its CNS depressant effects, patients receiving
alprazolam should be cautioned against engaging in hazardous occupations or
activities requiring complete mental alertness such as operating machinery or
driving a motor vehicle. For the same reason, patients should be cautioned about
the simultaneous ingestion of alcohol and other CNS depressant drugs during
treatment with alprazolam.
Risk of Fetal Harm
Benzodiazepines can potentially cause fetal harm when
administered to pregnant women. If alprazolam is used during pregnancy, or if
the patient becomes pregnant while taking this drug, the patient should be
apprised of the potential hazard to the fetus. Because of experience with other
members of the benzodiazepine class, alprazolam is assumed to be capable of
causing an increased risk of congenital abnormalities when administered to a
pregnant woman during the first trimester. Because use of these drugs is rarely
a matter of urgency, their use during the first trimester should almost always
be avoided. The possibility that a woman of childbearing potential may be
pregnant at the time of institution of therapy should be considered. Patients
should be advised that if they become pregnant during therapy or intend to
become pregnant they should communicate with their physicians about the
desirability of discontinuing the drug.
Alprazolam Interaction With Drugs That Inhibit
Metabolism Via Cytochrome P450 3A
The initial step in alprazolam metabolism is hydroxylation
catalyzed by cytochrome P450 3A (CYP3A). Drugs that inhibit this metabolic
pathway may have a profound effect on the clearance of alprazolam. Consequently,
alprazolam should be avoided in patients receiving very potent inhibitors of
CYP3A. With drugs inhibiting CYP3A to a lesser but still significant degree,
alprazolam should be used only with caution and consideration of appropriate
dosage reduction. For some drugs, an interaction with alprazolam has been
quantified with clinical data; for other drugs, interactions are predicted from
in vitro data and/or experience with similar drugs in
the same pharmacologic class.
The following are examples of drugs known to inhibit the metabolism of
alprazolam and/or related benzodiazepines, presumably through inhibition of
CYP3A.
Potent CYP3A InhibitorsAzole Antifungal Agents
Ketoconazole and itraconazole are potent CYP3A inhibitors and
have been shown in vivo to increase plasma alprazolam
concentrations 3.98 fold and 2.7 fold, respectively. The coadministration of
alprazolam with these agents is not recommended. Other azole-type antifungal
agents should also be considered potent CYP3A inhibitors and the
coadministration of alprazolam with them is not recommended (see CONTRAINDICATIONS).
Drugs demonstrated to be CYP3A inhibitors on the
basis of clinical studies involving alprazolam (caution and consideration of
appropriate alprazolam dose reduction are recommended during coadministration
with the following drugs)Nefazodone
Coadministration of nefazodone increased alprazolam concentration
two-fold.
Fluvoxamine
Coadministration of fluvoxamine approximately doubled the maximum
plasma concentration of alprazolam, decreased clearance by 49%, increased
half-life by 71%, and decreased measured psychomotor performance.
Cimetidine
Coadministration of cimetidine increased the maximum plasma
concentration of alprazolam by 86%, decreased clearance by 42%, and increased
half-life by 16%.
Other Drugs Possibly Affecting Alprazolam
Metabolism
Other drugs possibly affecting alprazolam metabolism by
inhibition of CYP3A are discussed in the PRECAUTIONS section (see PRECAUTIONS: Drug
Interactions).