Overdose
Deaths may occur from overdosage with this class of drugs. Multiple drug ingestion (including
alcohol) is common in deliberate tricyclic overdose. As the management is complex and changing, it is
recommended that the physician contact a poison control center for current information on treatment.
Signs and symptoms of toxicity develop rapidly after tricyclic overdose. Therefore, hospital
monitoring is required as soon as possible.
Children have been reported to be more sensitive than adults to an acute overdosage of imipramine
hydrochloride. An acute overdose of any amount in infants or young children, especially, must be
considered serious and potentially fatal.
Manifestations
These may vary in severity depending upon factors such as the amount of drug absorbed, the age of the
patient, and the interval between drug ingestion and the start of treatment. Critical manifestations of
overdose include cardiac dysrhythmias, severe hypotension, convulsions, and CNS depression
including coma. Changes in the electrocardiogram, particularly in QRS axis or width, are clinically
significant indicators of tricyclic toxicity.
Other CNS manifestations may include drowsiness, stupor, ataxia, restlessness, agitation, hyperactive
reflexes, muscle rigidity, athetoid and choreiform movements.
Cardiac abnormalities may include tachycardia and signs of congestive failure. Respiratory depression,
cyanosis, shock, vomiting, hyperpyrexia, mydriasis, and diaphoresis may also be present.
Management
Obtain an ECG and immediately initiate cardiac monitoring. Protect the patient's airway, establish an
intravenous line and initiate gastric decontamination. A minimum of 6 hours of observation with cardiac
monitoring and observation for signs of CNS or respiratory depression, hypotension, cardiac
dysrhythmias and/or conduction blocks, and seizures is necessary. If signs of toxicity occur at anytime
during this period, extended monitoring is required. There are case reports of patients succumbing to
fatal dysrhythmias late after overdose; these patients had clinical evidence of significant poisoning
prior to death and most received inadequate gastrointestinal decontamination. Monitoring of plasma drug
levels should not guide management of the patient.
Gastrointestinal Decontamination
All patients suspected of tricyclic overdose should receive
gastrointestinal decontamination. This should include large volume gastric lavage followed by activated
charcoal. If consciousness is impaired, the airway should be secured prior to lavage. Emesis is
contraindicated.
Cardiovascular
A maximal limb-lead QRS duration of ≥0.10 seconds may be the best indication of
the severity of the overdose. Intravenous sodium bicarbonate should be used to maintain the serum pH in
the range of 7.45 to 7.55. If the pH response is inadequate, hyperventilation may also be used.
Concomitant use of hyperventilation and sodium bicarbonate should be done with extreme caution, with
frequent pH monitoring. A pH >7.60 or a pCO2 <20 mmHg is undesirable. Dysrhythmias unresponsive
to sodium bicarbonate therapy/hyperventilation may respond to lidocaine, bretylium, or phenytoin. Type
1A and 1C antiarrhythmics are generally contraindicated (e.g., quinidine, disopyramide, and
procainamide).
In rare instances, hemoperfusion may be beneficial in acute refractory cardiovascular instability in
patients with acute toxicity. However, hemodialysis, peritoneal dialysis, exchange transfusions, and
forced diuresis generally have been reported as ineffective in tricyclic poisoning.
CNS
In patients with CNS depression, early intubation is advised because of the potential for abrupt
deterioration. Seizures should be controlled with benzodiazepines, or if these are ineffective, other
anticonvulsants (e.g., phenobarbital, phenytoin). Physostigmine is not recommended except to treat lifethreatening
symptoms that have been unresponsive to other therapies, and then only in consultation with a
poison control center.
Psychiatric Follow-Up
Since overdosage is often deliberate, patients may attempt suicide by other
means during the recovery phase. Psychiatric referral may be appropriate.
Pediatric Management
The principles of management of child and adult overdosages are similar. It
is strongly recommended that the physician contact the local poison control center for specific pediatric
treatment.
Contraindications
The concomitant use of monoamine oxidase inhibiting compounds is contraindicated. Hyperpyretic
crises or severe convulsive seizures may occur in patients receiving such combinations. The
potentiation of adverse effects can be serious, or even fatal. When it is desired to substitute Tofranil in
patients receiving a monoamine oxidase inhibitor, as long an interval should elapse as the clinical
situation will allow, with a minimum of 14 days. Initial dosage should be low and increases should be
gradual and cautiously prescribed.
The drug is contraindicated during the acute recovery period after a myocardial infarction. Patients with
a known hypersensitivity to this compound should not be given the drug. The possibility of crosssensitivity
to other dibenzazepine compounds should be kept in mind.
Undesirable effects
Note – Although the listing which follows includes a few adverse reactions which have not been
reported with this specific drug, the pharmacological similarities among the tricyclic antidepressant
drugs require that each of the reactions be considered when Tofranil is administered.
Cardiovascular: Orthostatic hypotension, hypertension, tachycardia, palpitation, myocardial infarction,
arrhythmias, heart block, ECG changes, precipitation of congestive heart failure, stroke.
Psychiatric: Confusional states (especially in the elderly) with hallucinations, disorientation, delusions;
anxiety, restlessness, agitation; insomnia and nightmares; hypomania; exacerbation of psychosis.
Neurological: Numbness, tingling, paresthesias of extremities; incoordination, ataxia, tremors;
peripheral neuropathy; extrapyramidal symptoms; seizures, alterations in EEG patterns; tinnitus.
Anticholinergic: Dry mouth, and, rarely, associated sublingual adenitis; blurred vision, disturbances of
accommodation, mydriasis; constipation, paralytic ileus; urinary retention, delayed micturition, dilation
of the urinary tract.
Allergic: Skin rash, petechiae, urticaria, itching, photosensitization; edema (general or of face and
tongue); drug fever; cross-sensitivity with desipramine.
Hematologic: Bone marrow depression including agranulocytosis; eosinophilia; purpura;
thrombocytopenia.
Gastrointestinal: Nausea and vomiting, anorexia, epigastric distress, diarrhea; peculiar taste, stomatitis,
abdominal cramps, black tongue.
Endocrine: Gynecomastia in the male; breast enlargement and galactorrhea in the female; increased or
decreased libido, impotence; testicular swelling; elevation or depression of blood sugar levels;
inappropriate antidiuretic hormone (ADH) secretion syndrome.
Other: Jaundice (simulating obstructive); altered liver function; weight gain or loss; perspiration;
flushing; urinary frequency; drowsiness, dizziness, weakness and fatigue; headache; parotid swelling;
alopecia; proneness to falling.
Withdrawal Symptoms: Though not indicative of addiction, abrupt cessation of treatment after prolonged
therapy may produce nausea, headache, and malaise.
Note – In enuretic children treated with Tofranil the most common adverse reactions have been
nervousness, sleep disorders, tiredness, and mild gastrointestinal disturbances. These usually disappear
during continued drug administration or when dosage is decreased. Other reactions which have been
reported include constipation, convulsions, anxiety, emotional instability, syncope, and collapse. All of
the adverse effects reported with adult use should be considered.
Therapeutic indications
Depression
For the relief of symptoms of depression. Endogenous depression is more likely to be
alleviated than other depressive states. One to three weeks of treatment may be needed before optimal
therapeutic effects are evident.
Childhood Enuresis
May be useful as temporary adjunctive therapy in reducing enuresis in children
aged 6 years and older, after possible organic causes have been excluded by appropriate tests. In
patients having daytime symptoms of frequency and urgency, examination should include voiding
cystourethrography and cystoscopy, as necessary. The effectiveness of treatment may decrease with
continued drug administration.
Date of revision of the text
Apr 2017
Name of the medicinal product
Tofranil
Fertility, pregnancy and lactation
Animal reproduction studies have yielded inconclusive results (see also Animal Pharmacology).
There have been no well-controlled studies conducted with pregnant women to determine the effect of
Tofranil on the fetus. However, there have been clinical reports of congenital malformations associated
with the use of the drug. Although a causal relationship between these effects and the drug could not be
established, the possibility of fetal risk from the maternal ingestion of Tofranil cannot be excluded.
Therefore, Tofranil should be used in women who are or might become pregnant only if the clinical
condition clearly justifies potential risk to the fetus.
Qualitative and quantitative composition
The three strengths of Tofranil™ (imipramine hydrochloride USP) are available as follows:
Tablets 10 mg – triangular, biconvex, coral-reddish brown, sugar-coated tablet, imprinted with on one
side and “10” on the other side in black.
Bottles of 30 NDC 0406-9920-03
Bottles of 100 NDC 0406-9920-01
Tablets 25 mg – round, biconvex, coral-reddish brown, sugar-coated tablet, imprinted with on one
side and “25” on the other side in black.
Bottles of 30 NDC 0406-9921-03
Bottles of 100 NDC 0406-9921-01
Tablets 50 mg – round, biconvex, coral-reddish brown, sugar-coated tablet, imprinted with on one
side and “50” on the other side in black.
Bottles of 30 NDC 0406-9922-03
Bottles of 100 NDC 0406-9922-01
Store at 20° to 25°C (68° to 77°F).
Dispense in tight container (USP) with a child-resistant closure.
Manufactured by: Patheon Inc. Whitby, Ontario, Canada, L1N 5Z5. Revised: Apr 2017
Special warnings and precautions for use
WARNINGS
Clinical Worsening And Suicide Risk
Patients with major depressive disorder (MDD), both adult and pediatric, may experience worsening of
their depression and/or the emergence of suicidal ideation and behavior (suicidality) or unusual changes
in behavior, whether or not they are taking antidepressant medications, and this risk may persist until
significant remission occurs. Suicide is a known risk of depression and certain other psychiatric
disorders, and these disorders themselves are the strongest predictors of suicide. There has been a
long-standing concern, however, that antidepressants may have a role in inducing worsening of
depression and the emergence of suicidality in certain patients during the early phases of treatment.
Pooled analyses of short-term placebo-controlled trials of antidepressant drugs (SSRIs and others)
showed that these drugs increase the risk of suicidal thinking and behavior (suicidality) in children,
adolescents, and young adults (ages 18 to 24) with major depressive disorder (MDD) and other
psychiatric disorders. Short-term studies did not show an increase in the risk of suicidality with
antidepressants compared to placebo in adults beyond age 24; there was a reduction with antidepressants
compared to placebo in adults aged 65 and older.
The pooled analyses of placebo-controlled trials in children and adolescents with MDD, obsessive
compulsive disorder (OCD), or other psychiatric disorders included a total of 24 short-term trials of 9
antidepressant drugs in over 4400 patients. The pooled analyses of placebo-controlled trials in adults
with MDD or other psychiatric disorders included a total of 295 short-term trials (median duration of 2
months) of 11 antidepressant drugs in over 77,000 patients. There was considerable variation in risk of
suicidality among drugs, but a tendency toward an increase in the younger patients for almost all drugs
studied. There were differences in absolute risk of suicidality across the different indications, with the
highest incidence in MDD. The risk differences (drug vs. placebo), however, were relatively stable
within age strata and across indications. These risk differences (drug-placebo difference in the number
of cases of suicidality per 1000 patients treated) are provided in Table 1.
Table 1
| Age Range |
Drug-Placebo Difference in Number of Cases of Suicidality per 1000 Patients Treated |
| Increases Compared to Placebo |
| <18 |
14 additional cases |
| 18 - 24 |
5 additional cases |
| Decreases Compared to Placebo |
| 25 - 64 |
1 fewer case |
| ≥65 |
6 fewer cases |
No suicides occurred in any of the pediatric trials. There were suicides in the adult trials, but the
number was not sufficient to reach any conclusion about drug effect on suicide.
It is unknown whether the suicidality risk extends to longer-term use, i.e., beyond several months.
However, there is substantial evidence from placebo-controlled maintenance trials in adults with
depression that the use of antidepressants can delay the recurrence of depression.
All patients being treated with antidepressants for any indication should be monitored
appropriately and observed closely for clinical worsening, suicidality, and unusual changes in
behavior, especially during the initial few months of a course of drug therapy, or at times of dose
changes, either increases or decreases.
The following symptoms, anxiety, agitation, panic attacks, insomnia, irritability, hostility,
aggressiveness, impulsivity, akathisia (psychomotor restlessness), hypomania, and mania, have been
reported in adult and pediatric patients being treated with antidepressants for major depressive disorder
as well as for other indications, both psychiatric and nonpsychiatric. Although a causal link between the
emergence of such symptoms and either the worsening of depression and/or the emergence of suicidal
impulses has not been established, there is concern that such symptoms may represent precursors to
emerging suicidality.
Consideration should be given to changing the therapeutic regimen, including possibly discontinuing
the medication, in patients whose depression is persistently worse, or who are experiencing emergent
suicidality or symptoms that might be precursors to worsening depression or suicidality, especially if
these symptoms are severe, abrupt in onset, or were not part of the patient's presenting symptoms.
Families and caregivers of patients being treated with antidepressants for major depressive
disorder or other indications, both psychiatric and nonpsychiatric, should be alerted about the
need to monitor patients for the emergence of agitation, irritability, unusual changes in behavior,
and the other symptoms described above, as well as the emergence of suicidality, and to report
such symptoms immediately to healthcare providers. Such monitoring should include daily
observation by families and caregivers. Prescriptions for imipramine hydrochloride should be written
for the smallest quantity of tablets consistent with good patient management, in order to reduce the risk
of overdose.
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 imipramine
hydrochloride is not approved for use in treating bipolar depression.
Angle-Closure Glaucoma
The pupillary dilation that occurs following use of many antidepressant
drugs including Tofranil may trigger an angle-closure attack in a patient with anatomically narrow
angles who does not have a patent iridectomy.
Children
A dose of 2.5 mg/kg/day of Tofranil should not be exceeded in childhood. ECG changes of
unknown significance have been reported in pediatric patients with doses twice this amount.
Extreme caution should be used when this drug is given to: patients with cardiovascular disease
because of the possibility of conduction defects, arrhythmias, congestive heart failure, myocardial
infarction, strokes, and tachycardia. These patients require cardiac surveillance at all dosage levels of
the drug;
patients with history of urinary retention, or history of narrow-angle glaucoma because of the drug's
anticholinergic properties; hyperthyroid patients or those on thyroid medication because of the
possibility of cardiovascular toxicity;
patients with a history of seizure disorder because this drug has been shown to lower the seizure
threshold;
patients receiving guanethidine, clonidine, or similar agents, since Tofranil may block the
pharmacologic effects of these drugs;
patients receiving methylphenidate hydrochloride. Since methylphenidate hydrochloride may inhibit the
metabolism of Tofranil, downward dosage adjustment of imipramine hydrochloride may be required
when given concomitantly with methylphenidate hydrochloride.
Tofranil may enhance the CNS depressant effects of alcohol. Therefore, it should be borne in mind that
the dangers inherent in a suicide attempt or accidental overdosage with the drug may be increased for
the patient who uses excessive amounts of alcohol (see PRECAUTIONS).
Since Tofranil may impair the mental and/or physical abilities required for the performance of
potentially hazardous tasks, such as operating an automobile or machinery, the patient should be
cautioned accordingly.
PRECAUTIONS
General
An ECG recording should be taken prior to the initiation of larger-than-usual doses of Tofranil and at
appropriate intervals thereafter until steady state is achieved. (Patients with any evidence of
cardiovascular disease require cardiac surveillance at all dosage levels of the drug. See WARNINGS.)
Elderly patients and patients with cardiac disease or a prior history of cardiac disease are at special risk
of developing the cardiac abnormalities associated with the use of Tofranil.
It should be kept in mind that the possibility of suicide in seriously depressed patients is inherent in the
illness and may persist until significant remission occurs. Such patients should be carefully supervised
during the early phase of treatment with Tofranil, and may require hospitalization. Prescriptions should
be written for the smallest amount feasible. Hypomanic or manic episodes may occur, particularly in
patients with cyclic disorders. Such reactions may necessitate discontinuation of the drug. If needed,
Tofranil may be resumed in lower dosage when these episodes are relieved.
Administration of a tranquilizer may be useful in controlling such episodes.
An activation of the psychosis may occasionally be observed in schizophrenic patients and may require
reduction of dosage and the addition of a phenothiazine.
Concurrent administration of Tofranil with electroshock therapy may increase the hazards; such
treatment should be limited to those patients for whom it is essential, since there is limited clinical
experience.
Patients taking imipramine hydrochloride should avoid excessive exposure to sunlight since there have
been reports of photosensitization.
Both elevation and lowering of blood sugar levels have been reported with imipramine hydrochloride
use.
Imipramine hydrochloride should be used with caution in patients with significantly impaired renal or
hepatic function.
Patients who develop a fever and a sore throat during therapy with imipramine hydrochloride should
have leukocyte and differential blood counts performed. Imipramine hydrochloride should be
discontinued if there is evidence of pathological neutrophil depression.
Prior to elective surgery, imipramine hydrochloride should be discontinued for as long as the clinical
situation will allow.
Information For Patients
Prescribers or other health professionals should inform patients, their families, and their caregivers
about the benefits and risks associated with treatment with imipramine hydrochloride and should counsel
them in its appropriate use. A patient Medication Guide about "Antidepressant Medicines, Depression
and other Serious Mental Illness, and Suicidal Thoughts or Actions" is available for imipramine
hydrochloride. The prescriber or health professional should instruct patients, their families, and their
caregivers to read the Medication Guide and should assist them in understanding its contents. Patients
should be given the opportunity to discuss the contents of the Medication Guide and to obtain answers
to any questions they may have. The complete text of the Medication Guide is reprinted at the end of this
document.
Patients should be advised of the following issues and asked to alert their prescriber if these occur
while taking imipramine hydrochloride.
Patients should be advised that taking Tofranil can cause mild pupillary dilation, which in susceptible
individuals, can lead to an episode of angle-closure glaucoma. Pre-existing glaucoma is almost always
open-angle glaucoma because angle-closure glaucoma, when diagnosed, can be treated definitively
with iridectomy. Open-angle glaucoma is not a risk factor for angle-closure glaucoma. Patients may
wish to be examined to determine whether they are susceptible to angle closure, and have a
prophylactic procedure (e.g., iridectomy), if they are susceptible.
Clinical Worsening And Suicide Risk
Patients, their families, and their caregivers should be
encouraged to be alert to the emergence of anxiety, agitation, panic attacks, insomnia, irritability,
hostility, aggressiveness, impulsivity, akathisia (psychomotor restlessness), hypomania, mania, other
unusual changes in behavior, worsening of depression, and suicidal ideation, especially early during
antidepressant treatment and when the dose is adjusted up or down. Families and caregivers of patients
should be advised to look for the emergence of such symptoms on a day-to-day basis, since changes
may be abrupt. Such symptoms should be reported to the patient’s prescriber or health professional,
especially if they are severe, abrupt in onset, or were not part of the patient’s presenting symptoms.
Symptoms such as these may be associated with an increased risk for suicidal thinking and behavior and
indicate a need for very close monitoring and possibly changes in the medication.
Pregnancy
Animal reproduction studies have yielded inconclusive results (see also Animal Pharmacology).
There have been no well-controlled studies conducted with pregnant women to determine the effect of
Tofranil on the fetus. However, there have been clinical reports of congenital malformations associated
with the use of the drug. Although a causal relationship between these effects and the drug could not be
established, the possibility of fetal risk from the maternal ingestion of Tofranil cannot be excluded.
Therefore, Tofranil should be used in women who are or might become pregnant only if the clinical
condition clearly justifies potential risk to the fetus.
Nursing Mothers
Limited data suggest that Tofranil is likely to be excreted in human breast milk. As a general rule, a
woman taking a drug should not nurse since the possibility exists that the drug may be excreted in breast
milk and be harmful to the child.
Pediatric Use
Safety and effectiveness in the pediatric population other than pediatric patients with nocturnal enuresis
have not been established (see BOX WARNING and WARNINGS, Clinical Worsening and Suicide
Risk). Anyone considering the use of imipramine hydrochloride in a child or adolescent must balance
the potential risks with the clinical need.
The safety and effectiveness of the drug as temporary adjunctive therapy for nocturnal enuresis in
pediatric patients less than 6 years of age has not been established.
The safety of the drug for long-term, chronic use as adjunctive therapy for nocturnal enuresis in
pediatric patients 6 years of age or older has not been established; consideration should be given to
instituting a drug-free period following an adequate therapeutic trial with a favorable response.
A dose of 2.5 mg/kg/day should not be exceeded in childhood. ECG changes of unknown significance
have been reported in pediatric patients with doses twice this amount.
Geriatric Use
In the literature, there were four well-controlled, randomized, double-blind, parallel group comparison
clinical studies done with Tofranil in the elderly population. There was a total number of 651 subjects
included in these studies. These studies did not provide a comparison to younger subjects. There were
no additional adverse experiences identified in the elderly.
Clinical studies of Tofranil in the original application did not include sufficient numbers of subjects
aged 65 and over to determine whether they respond differently from younger subjects. Postmarketing
clinical experience has not identified differences in responses between the elderly and younger
subjects. In general, dose selection for the elderly should be cautious, usually starting at the low end of
the dosing range, reflecting greater frequency of decreased hepatic, renal, or cardiac function, and of
concomitant disease or other drug therapy.
(See also DOSAGE AND ADMINISTRATION, Adolescent and Geriatric Patients.)
(See also PRECAUTIONS, General.)
Dosage (Posology) and method of administration
Depression
Lower dosages are recommended for elderly patients and adolescents. Lower dosages are also
recommended for outpatients as compared to hospitalized patients who will be under close supervision.
Dosage should be initiated at a low level and increased gradually, noting carefully the clinical response
and any evidence of intolerance. Following remission, maintenance medication may be required for a
longer period of time, at the lowest dose that will maintain remission.
Usual Adult Dose
Hospitalized Patients
Initially, 100 mg/day in divided doses gradually increased to 200 mg/day as
required. If no response after two weeks, increase to 250 to 300 mg/day.
Outpatients
Initially, 75 mg/day increased to 150 mg/day. Dosages over 200 mg/day are not
recommended. Maintenance, 50 to 150 mg/day.
Adolescent And Geriatric Patients
Initially, 30 to 40 mg/day; it is generally not necessary to exceed
100 mg/day.
Childhood Enuresis
Initially, an oral dose of 25 mg/day should be tried in children aged 6 and older. Medication should be
given one hour before bedtime. If a satisfactory response does not occur within one week, increase the
dose to 50 mg nightly in children under 12 years; children over 12 may receive up to 75 mg nightly. A
daily dose greater than 75 mg does not enhance efficacy and tends to increase side effects. Evidence
suggests that in early night bedwetters, the drug is more effective given earlier and in divided amounts,
i.e., 25 mg in midafternoon, repeated at bedtime. Consideration should be given to instituting a drug free
period following an adequate therapeutic trial with a favorable response. Dosage should be tapered off
gradually rather than abruptly discontinued; this may reduce the tendency to relapse. Children who
relapse when the drug is discontinued do not always respond to a subsequent course of treatment.
A dose of 2.5 mg/kg/day should not be exceeded. ECG changes of unknown significance have been
reported in pediatric patients with doses twice this amount.
The safety and effectiveness of Tofranil as temporary adjunctive therapy for nocturnal enuresis in
children less than 6 years of age has not been established.
Interaction with other medicinal products and other forms of interaction
SIDE EFFECTS
Note – Although the listing which follows includes a few adverse reactions which have not been
reported with this specific drug, the pharmacological similarities among the tricyclic antidepressant
drugs require that each of the reactions be considered when Tofranil is administered.
Cardiovascular: Orthostatic hypotension, hypertension, tachycardia, palpitation, myocardial infarction,
arrhythmias, heart block, ECG changes, precipitation of congestive heart failure, stroke.
Psychiatric: Confusional states (especially in the elderly) with hallucinations, disorientation, delusions;
anxiety, restlessness, agitation; insomnia and nightmares; hypomania; exacerbation of psychosis.
Neurological: Numbness, tingling, paresthesias of extremities; incoordination, ataxia, tremors;
peripheral neuropathy; extrapyramidal symptoms; seizures, alterations in EEG patterns; tinnitus.
Anticholinergic: Dry mouth, and, rarely, associated sublingual adenitis; blurred vision, disturbances of
accommodation, mydriasis; constipation, paralytic ileus; urinary retention, delayed micturition, dilation
of the urinary tract.
Allergic: Skin rash, petechiae, urticaria, itching, photosensitization; edema (general or of face and
tongue); drug fever; cross-sensitivity with desipramine.
Hematologic: Bone marrow depression including agranulocytosis; eosinophilia; purpura;
thrombocytopenia.
Gastrointestinal: Nausea and vomiting, anorexia, epigastric distress, diarrhea; peculiar taste, stomatitis,
abdominal cramps, black tongue.
Endocrine: Gynecomastia in the male; breast enlargement and galactorrhea in the female; increased or
decreased libido, impotence; testicular swelling; elevation or depression of blood sugar levels;
inappropriate antidiuretic hormone (ADH) secretion syndrome.
Other: Jaundice (simulating obstructive); altered liver function; weight gain or loss; perspiration;
flushing; urinary frequency; drowsiness, dizziness, weakness and fatigue; headache; parotid swelling;
alopecia; proneness to falling.
Withdrawal Symptoms: Though not indicative of addiction, abrupt cessation of treatment after prolonged
therapy may produce nausea, headache, and malaise.
Note – In enuretic children treated with Tofranil the most common adverse reactions have been
nervousness, sleep disorders, tiredness, and mild gastrointestinal disturbances. These usually disappear
during continued drug administration or when dosage is decreased. Other reactions which have been
reported include constipation, convulsions, anxiety, emotional instability, syncope, and collapse. All of
the adverse effects reported with adult use should be considered.
DRUG INTERACTIONS
Drugs Metabolized By P450 2D6
The biochemical activity of the drug metabolizing isozyme
cytochrome P450 2D6 (debrisoquin hydroxylase) is reduced in a subset of the Caucasian population
(about 7% to 10% of Caucasians are so-called “poor metabolizers”); reliable estimates of the
prevalence of reduced P450 2D6 isozyme activity among Asian, African, and other populations are not
yet available. Poor metabolizers have higher than expected plasma concentrations of tricyclic
antidepressants (TCAs) when given usual doses. Depending on the fraction of drug metabolized by
P450 2D6, the increase in plasma concentration may be small, or quite large (8-fold increase in plasma
AUC of the TCA).
In addition, certain drugs inhibit the activity of this isozyme and make normal metabolizers resemble
poor metabolizers. An individual who is stable on a given dose of TCA may become abruptly toxic
when given one of these inhibiting drugs as concomitant therapy. The drugs that inhibit cytochrome
P450 2D6 include some that are not metabolized by the enzyme (quinidine; cimetidine) and many that are
substrates for P450 2D6 (many other antidepressants, phenothiazines, and the Type 1C antiarrhythmics
propafenone and flecainide). While all the selective serotonin reuptake inhibitors (SSRIs), e.g.,
fluoxetine, sertraline, and paroxetine, inhibit P450 2D6, they may vary in the extent of inhibition. The
extent to which SSRI-TCA interaction may pose clinical problems will depend on the degree of
inhibition and the pharmacokinetics of the SSRI involved. Nevertheless, caution is indicated in the
coadministration of TCAs with any of the SSRIs and also in switching from one class to the other. Of
particular importance, sufficient time must elapse before initiating TCA treatment in a patient being
withdrawn from fluoxetine, given the long half-life of the parent and active metabolite (at least 5 weeks
may be necessary).
Concomitant use of tricyclic antidepressants with drugs that can inhibit cytochrome P450 2D6 may
require lower doses than usually prescribed for either the tricyclic antidepressant or the other drug.
Furthermore, whenever one of these other drugs is withdrawn from co-therapy, an increased dose of
tricyclic antidepressant may be required. It is desirable to monitor TCA plasma levels whenever a TCA
is going to be coadministered with another drug known to be an inhibitor of P450 2D6.
The plasma concentration of imipramine may increase when the drug is given concomitantly with hepatic
enzyme inhibitors (e.g., cimetidine, fluoxetine) and decrease by concomitant administration with hepatic
enzyme inducers (e.g., barbiturates, phenytoin), and adjustment of the dosage of imipramine may
therefore be necessary.
In occasional susceptible patients or in those receiving anticholinergic drugs (including
antiparkinsonism agents) in addition, the atropine-like effects may become more pronounced (e.g.,
paralytic ileus). Close supervision and careful adjustment of dosage is required when imipramine
hydrochloride is administered concomitantly with anticholinergic drugs.
Avoid the use of preparations, such as decongestants and local anesthetics, that contain any
sympathomimetic amine (e.g., epinephrine, norepinephrine), since it has been reported that tricyclic
antidepressants can potentiate the effects of catecholamines.
Caution should be exercised when imipramine hydrochloride is used with agents that lower blood
pressure. Imipramine hydrochloride may potentiate the effects of CNS depressant drugs.
Patients should be warned that imipramine hydrochloride may enhance the CNS depressant effects of
alcohol (see WARNINGS).