GENERIC NAME: promethazine
BRAND NAME: Phenergan
DRUG CLASS AND MECHANISM: Promethazine is a
phenothiazine in the
same class of drugs as chlorpromazine (Thorazine) and
trifluoperazine
(Stelazine); however, unlike the other drugs in this class,
promethazine
is not used clinically as an anti-psychotic. It acts as an anti-histamine,
a sedative, and an anti-emetic (anti-nausea). Promethazine is
used
principally as an anti-emetic, to prevent motion sickness or as
an
anti-histamine in combination with other medications in cough
and cold
preparations. Promethazine was approved by the FDA in 1951.
PRESCRIPTION: yes
GENERIC AVAILABLE: yes
PREPARATIONS: Tablets: 12.5, 25, and 50
mg. Suppositories: 25mg.
It also is available as an injectable medication.
STORAGE: Tablets and suppositories should be stored
between 2°
(36°F) and 30°C (86°F).
PRESCRIBED FOR: Promethazine is used to prevent motion
sickness,
nausea or vomiting, itching associated with allergies or for
sedation.
DOSING: Tablets may be taken with or without food.
Suppositories
are unwrapped and moistened with water before insertion into
the rectum.
If the suppository is too soft from being stored in a warm
place, it can
be hardened by chilling in the refrigerator for 20 to 30
minutes or
placing in cold water before the wrapper is removed.
For prevention of motion sickness, a tablet or suppository
should be
used 30 to 60 minutes before the motion begins and then every 8
to 12
hours as needed. For sedation, it is given at bedtime. For
other problems,
for example, itching, it can be given every 4 to 8 hours.
Promethazine should not be used in children less than two years of age
because it can depress respiration and has caused fatalities in children under
two. It should be used cautiously in children older than two.
DRUG INTERACTIONS: Promethazine should not be taken
with any of
the MAO (mono-amine oxidase) inhibitor-class of
antidepressants, for
example, isocarboxazid (Marplan), phenelzine (Nardil),
tranylcypromine
(Parnate), and procarbazine (Matulane), since the effects of
both drugs
add to each other and lead to complications.
Excessive anti-cholinergic effects (described below) can occur
when
promethazine is used with any of the following: some
antihistamines, e.g.,
carbinoxamine (Rondec), clemastine (Tavist), diphenhydramine
(Benadryl);
some phenothiazines, e.g., thioridazine (Mellaril),
triflupromazine
(Stelazine); some tricyclic antidepressants, e.g.,
amitriptyline (Elavil),
amoxapine (Asendin), clomipramine (Anafranil), protriptyline
(Vivactil);
clozapine (Clozaril), cyclobenzaprine (Flexeril), and
disopyramide
(Norpace). Anticholinergic side effects are listed under SIDE
EFFECTS
below.
Excessive sedation may occur when promethazine is combined
with other
medications that depress the central nervous system (brain).
Such drugs
include ethanol, barbiturates, anti-anxiety medications,
sedatives, other
phenothiazines, and narcotic pain medications.
There may be an increase in the risk of certain neurologic
reactions
that affect movement of muscles, called extrapyramidal symptoms
(EPS),
when promethazine is used together with other medicines which
also cause
these reactions. Such drugs include antipsychotics,
metoclopramide
(Reglan), and amoxapine (Asendin).
Promethazine should not be used with propylthiouracil (PTU)
due to the
increased risk of dangerous drops in the white blood cell count
which can
increase the risk of infections. The reason for this
interaction is not
known.
Concurrent use of promethazine with the dye used for
myelography (x-rays
of the spinal cord) can lower the threshold for seizures and
thus increase
the risk of seizures. Promethazine should be stopped at least
48 hours
before myelography and not restarted until at least 24 hours
after
myelography.
PREGNANCY: There are no adequate studies of
promethazine in
pregnant women. However, studies in animals suggest no
important effects
on the fetus. Promethazine therefore can be used in pregnancy
if the
physician feels that it is needed. Anti-histamines in general
are not
recommended for use in pregnancy, especially during the third
trimester,
because they increase the risk for a seizure in the fetus.
NURSING MOTHERS: Anti-histamines
are not recommended for use during breast-feeding because they can stimulate
newborns or cause seizures in premature infants. Anti-histamines also inhibit
lactation (production of breast milk).
SIDE EFFECTS: Promethazine
often causes sedation and tiredness. In children less than two it can depress
respiration and lead to death and, therefore, should not be used in children less than two years
old.
Dizziness may also occur. Ironically, promethazine sometimes
stimulates
patients, particularly children. Such stimulation may be
manifest by
restlessness, inability to sleep, heart palpitations or even
seizures.
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From the Doctors at MedicineNet.com  |
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Back to Medications IndexLast Editorial Review: 10/16/2005
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