Screening Patients for Bipolar
Disorder:A major depressive episode may be the initial presentation of
bipolar disorder. It is generally believed (though not established in controlled
trials) that treating such an episode with an antidepressant alone may increase
the likelihood of precipitation of a mixed/manic episode in patients at risk for
bipolar disorder. Whether any of the symptoms described above represent such a
conversion is unknown. However, prior to initiating treatment with an
antidepressant, patients with depressive symptoms should be adequately screened
to determine if they are at risk for bipolar disorder; such screening should
include a detailed psychiatric history, including a family history of suicide,
bipolar disorder, and depression. It should be noted that amitriptyline
hydrochloride tablets are not approved for use in treating bipolar
depression.
Amitriptyline hydrochloride may block the antihypertensive action of
guanethidine or similarly acting compounds.
It should be used with caution in patients with a history of seizures and,
because of its atropine-like action, in patients with a history of urinary
retention, angle-closure glaucoma or increased intraocular pressure. In patients
with angle-closure glaucoma, even average doses may precipitate an attack.
Patients with cardiovascular disorders should be watched closely. Tricyclic
antidepressant drugs, including amitriptyline hydrochloride, particularly when
given in high doses, have been reported to produce arrhythmias, sinus
tachycardia, and prolongation of the conduction time. Myocardial infarction and
stroke have been reported with drugs of this class.
Close supervision is required when amitriptyline hydrochloride is given to
hyperthyroid patients or those receiving thyroid medication.
Amitriptyline hydrochloride may enhance the response to alcohol and the
effects of barbiturates and other CNS depressants. In patients who may use
alcohol excessively, it should be borne in mind that the potentiation may
increase the danger inherent in any suicide attempt or overdosage. Delirium has
been reported with concurrent administration of amitriptyline and
disulfiram.
Usage in Pregnancy:Pregnancy Category C –
Teratogenic effects were not observed in mice, rats, or rabbits
when amitriptyline was given orally at doses of 2 to 40 mg/kg/day (up to 13
times the maximum recommended human dose*). Studies in literature have shown
amitriptyline to be teratogenic in mice and hamsters when given by various
routes of administration at doses of 28 to 100 mg/kg/day (9 to 33 times the
maximum recommended human dose), producing multiple malformations. Another study
in the rat reported that an oral dose of 25 mg/kg/day (8 times the maximum
recommended human dose) produced delays in ossification of fetal vertebral
bodies without other signs of embryotoxicity. In rabbits, an oral dose of 60
mg/kg/day (20 times the maximum recommended human dose) was reported to cause
incomplete ossification of the cranial bones.
Amitriptyline has been shown to cross the placenta. Although a causal
relationship has not been established, there have been a few reports of adverse
events, including CNS effects, limb deformities, or developmental delay, in
infants whose mothers had taken amitriptyline during pregnancy. There are no
adequate and well-controlled studies in pregnant women. Amitriptyline
hydrochloride should be used during pregnancy only if the potential benefit to
the mother justifies the potential risk to the fetus.
Nursing Mothers:Amitriptyline is excreted into breast milk. In one report in
which a patient received amitriptyline 100 mg/day while nursing her infant,
levels of 83 to 141 ng/mL were detected in the mother's serum. Levels of 135 to
151 ng/mL were found in the breast milk, but no trace of the drug could be
detected in the infant's serum.
Because of the potential for serious adverse reactions in nursing infants
from amitriptyline, a decision should be made whether to discontinue nursing or
to discontinue the drug, taking into account the importance of the drug to the
mother.
Pediatric Use:Safety and effectiveness in the pediatric population have not
been established (see BOX WARNING and
WARNINGS-Clinical
Worsening and Suicide Risk). Anyone considering the use of
amitriptyline hydrochloride tablets in a child or adolescent must balance the
potential risks with the clinical need.
Geriatric Use:Clinical experience has not identified differences in responses
between elderly and younger patients. In general, dose selection for an elderly
patient should be cautious, usually starting at the low end of the dosing range,
reflecting the greater frequency of decreased hepatic function, concomitant
disease and other drug therapy in elderly patients.
Geriatric patients are particularly sensitive to the anticholinergic side
effects of tricyclic antidepressants including amitriptyline hydrochloride.
Peripheral anticholinergic effects include tachycardia, urinary retention,
constipation, dry mouth, blurred vision, and exacerbation of narrow-angle
glaucoma. Central nervous system anticholinergic effects include cognitive
impairment, psychomotor slowing, confusion, sedation, and delirium. Elderly
patients taking amitriptyline hydrochloride may be at increased risk for falls.
Elderly patients should be started on low doses of amitriptyline hydrochloride
and observed closely (see DOSAGE AND
ADMINISTRATION).
METABOLISM
Studies in man following oral administration of 14C-labeled drug indicated that amitriptyline is rapidly
absorbed and metabolized. Radioactivity of the plasma was practically
negligible, although significant amounts of radioactivity appeared in the urine
by 4 to 6 hours and one-half to one-third of the drug was excreted within 24
hours.
Amitriptyline is metabolized by N-demethylation and bridge hydroxylation in
man, rabbit and rat. Virtually the entire dose is excreted as glucuronide or
sulfate conjugate of metabolites, with little unchanged drug appearing in the
urine. Other metabolic pathways may be involved.