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Oral LD50' s in rats (mg/kg): hydralazine, 173 and 187; hydrochlorothiazide, 2750.
Signs and Symptoms
Hydralazine: Signs and symptoms of overdosage include hypotension, tachycardia, headache, and generalized skin flushing. Complications can include myocardial ischemia and subsequent myocardial infarction, cardiac arrhythmia and profound shock.
Hydrochlorothiazide: The most prominent feature of poisoning is acute loss of fluid and electrolytes.
Cardiovascular: Tachycardia, hypotension, and shock.
Neuromuscular: Weakness, confusion, dizziness, cramps of the calf muscles, paresthesia, fatigue, impairment of consciousness.
Digestive: Nausea, vomiting, thirst.
Combined Poisoning: Signs and symptoms may be aggravated or modified by concomitant intake of antihypertensive medication, barbiturates, curare, digitalis (hypokalemia), corticosteroids, narcotics, or alcohol.
There is no specific antidote.
The gastric contents should be evacuated, taking adequate precautions against aspiration and for protection of the airway. An activated charcoal slurry may be instilled if conditions permit. Dialysis may not be effective for elimination of hydralazine HCI and hydrochlorothiazide because of its plasma protein binding (see CLINICAL PHARMACOLOGY).
These manipulations may have to be omitted or carried out after cardiovascular status has been stabilized, since they might precipitate cardiac arrhythmias or increase the depth of shock.
Support of the cardiovascular system is of primary importance in suspected hydralazine overdosage. Shock should be treated with plasma expanders. The patient's legs should be kept raised and lost fluid and electrolytes (potassium, sodium) should be replaced. If possible, vasopressors should not be given, but if a vasopressor is required, care should be taken not to precipitate or aggravate cardiac arrhythmia. Tachycardia responds to beta blockers. Digitalization may be necessary, and renal function should be monitored and supported as required.
Anuria: hypersensitivity to this or other sulfonamide-derived drugs.
Last reviewed on RxList: 12/8/2004
This monograph has been modified to include the generic and brand name in many instances.
Additional Apresazide Information
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