| GENERIC NAME: quetiapine
BRAND NAME: Seroquel
DRUG CLASS AND MECHANISM: Quetiapine is an oral drug
that is used for treating psychoses, for example, schizophrenia. Although
the mechanism of action of quetiapine is unknown, like other anti-psychotics,
it inhibits communication between nerves of the brain. It does this by
blocking receptors on the nerves for several neurotransmitters, the chemicals
that nerves use to communicate with each other. It is thought that its
beneficial effect is due to blocking of the dopamine type 2 (D2) and serotonin
type 2 (5-HT2) receptors.
PREPARATIONS: Quetiapine is available as 25 mg (peach),
100 mg (yellow) and 200 mg (white) tablets.
STORAGE:Tablets should be stored at room temperature,
15-30°C (59-86°F).
PRESCRIBED FOR: Quetiapine is used to treat severe mental
disorders like schizophrenia, which are characterized by distorted thoughts,
perceptions, and emotions,.
DOSING: Quetiapine usually is taken twice or three times
per day. The dose usually is increased slowly over several days to weeks
to achieve the desired effect. Quetiapine can be taken with or without
food.
DRUG INTERACTIONS: Phenytoin (Dilantin) markedly decreases
the amount of quetiapine that is absorbed from the intestine and thereby
reduces its effectiveness. Thus, patients taking phenytoin require higher
doses of quetiapine.
Quetiapine can cause orthostatic hypotension, a drop in blood pressure
that occurs upon rising that may cause dizziness or light-headedness.
Diazepam (Valium) or related benzodiazepines and alcohol can promote the
orthostatic hypotension caused by quetiapine, and they should not be taken
together with quetiapine.
Quetiapine can add to the sedating effects of other drugs that cause
sedation. Such drugs include narcotic pain relievers (e.g. Percocet),
barbiturates, sedatives such as alprazolam (Xanax) and clonazepam (Klonopin),
ethanol, and blood pressure drugs that can cause orthostatic hypotension,
such as prazosin (Minipress) and terazosin (Hytrin).
Quetiapine is eliminated from the body by an enzyme in the liver called
cytochrome P450 3A. There is a concern that drugs that strongly interfere
with the enzyme, e.g., ketoconazole (Nizoral), itraconazole (Sporanox),
fluconazole (Diflucan), and erythromycin, clarithromycin (Biaxin), nefazodone
(Serzone), Verapamil (Calan, Isoptin, Verelan), or diltiazem (Cardizem,
Tiazac, Dilacor) may cause elevated and toxic levels of quetiapine.
PREGNANCY: There are no adequate studies of quetiapine
in pregnant women. Studies in animals are inconsistent. Some studies suggest
effects on the fetus and others show no effects. Quetiapine can be used
in pregnancy if the physician feels that it is necessary.
NURSING MOTHERS: Quetiapine is excreted in the milk
of animals during lactation. It is not known if it is excreted in human
milk, but it is recommended that women taking quetiapine not breast feed.
SIDE EFFECTS: Quetiapine can cause orthostatic hypotension
especially during the first 3-5 day period of treatment, when it is restarted
after temporary discontinuation, and after an increase in the dose. The
risk of orthostatic hypotension is about 1 in 100 (one of every hundred
patients who takes quetiapine). Quetiapine frequently causes tiredness
(1 in 5 patients), especially during the first 3-5 days of treatment.
Because of this tiredness, care should be exercised in any activity requiring
mental alertness, such as operating a motor vehicle (including automobiles)
or hazardous machinery. Less common side effects include seizures (1 in
125 patients) and hypothyroidism (1 in 250 patients).
As with other antipsychotics, long-term use of quetiapine may lead to
a potentially irreversible condition called tardive dyskinesia which consists
of involuntary movements of the jaw, lips, and tongue.
A potentially fatal complex referred to as neuroleptic malignant syndrome
(NMS) has been reported with antipsychotic drugs, and two possible cases
of NMS have been reported with quetiapine. Patients who develop NMS may
have high fevers, muscle rigidity, altered mental status, irregular pulse
or blood pressure, rapid heart rate, excessive sweating, and heart arrhythmias.
In animals, quetiapine has been associated with the development of cataracts,
and cataracts have been reported in patients using quetiapine for prolonged
periods. Although it is not clear if quetiapine is responsible for the
cataracts seen in humans, eye examinations by slit-lamp (to identify cataracts
before they impair vision) are recommended at the beginning of treatment
and every six months during treatment. If cataracts form, treatment should
be discontinued.
Quetiapine may increase blood concentrations of cholesterol and triglycerides
by 11% and 17%, respectively.
Although there is no clear link between quetiapine and diabetes, patients
should be tested during treatment for elevated blood-sugars. Additionally,
persons with risk factors for diabetes, including obesity or a family
history of diabetes, should have their fasting levels of blood sugar tested
before starting treatment and periodically throughout treatment to detect
the onset of diabetes. Any patient developing symptoms that suggest diabetes
during treatment should be tested for diabetes.
Caution! Before starting
to take this medicine, it is vital that you should consult your doctor!
Do not use it on your own initiative, without medical advice.
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