Indications and Usage
Essential hypertension, alone or as an adjunct.
Dosage and Administration
Initiate therapy in gradually increasing dosages; adjust according to individual response. Start with 10 mg four times daily for the first 2 to 4 days, increase to 25 mg four times daily for the balance of the first week. For the second and subsequent weeks, increase dosage to 50 mg four times daily. For maintenance, adjust dosage to the lowest effective levels.
The incidence of toxic reactions, particularly the L.E. cell syndrome, is high in the group of patients receiving large doses of hydrALAZINE.
In a few resistant patients, up to 300 mg of hydrALAZINE daily may be required for a significant antihypertensive effect. In such cases, a lower dosage of hydrALAZINE combined with a thiazide and/or reserpine or a beta blocker may be considered. However, when combining therapy, individual titration is essential to ensure the lowest possible therapeutic dose of each drug.
Contraindications
Hypersensitivity to hydrALAZINE; coronary artery disease; mitral valvular rheumatic heart disease.
Adverse Reactions
Adverse reactions with hydrALAZINE are usually reversible when dosage is reduced. However, in some cases it may be necessary to discontinue the drug. The following adverse reactions have been observed, but there has not been enough systematic collection of data to support an estimate of their frequency.
Common : Headache, anorexia, nausea, vomiting, diarrhea, palpitations, tachycardia, angina pectoris.
Less Frequent :
Digestive: constipation, paralytic ileus.
Cardiovascular: hypotension, paradoxical pressor response, edema.
Respiratory : dyspnea.
Neurologic: peripheral neuritis, evidenced by paresthesia, numbness, and tingling; dizziness; tremors; muscle cramps; psychotic reactions characterized by depression, disorientation, or anxiety.
Genitourinary: difficulty in urination.
Hematologic: blood dyscrasias, consisting of reduction in hemoglobin and red cell count, leukopenia, agranulocytosis, purpura; lymphadenopathy; splenomegaly.
Hypersensitive Reactions: rash, urticaria, pruritus, fever, chills, arthralgia, eosinophilia, and rarely, hepatitis.
Other: nasal congestion, flushing, lacrimation, conjunctivitis.
Overdosage
Acute Toxicity: No deaths due to acute poisoning have been reported. Highest known dose survived: adults, 10 g orally.
Oral LD 50 in rats: 173 and 187 mg/kg.
Signs and Symptoms: 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.
Treatment: 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. 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. Shock should be treated with plasma expanders. 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.
No experience has been reported with extracorporeal or peritoneal dialysis.
Description
HydrALAZINE hydrochloride, USP, is an antihypertensive, for oral administration. Its chemical name is 1-hydrazinophthalazine monohydrochloride, and its structural formula is:
HydrALAZINE hydrochloride, USP is a white to off-white, odorless crystalline powder. It is soluble in water, slightly soluble in alcohol, and very slightly soluble in ether. It melts at about 275°C, with decomposition, and has a molecular weight of 196.64.
Each tablet for oral administration contains 10 mg, 25 mg, 50 mg, or 100 mg hydrALAZINE hydrochloride, USP. Tablets also contain FD&C Red #40/Allura Red AC Aluminum Lake, hypromellose, lactose anhydrous, light mineral oil, microcrystalline cellulose, magnesium stearate, pregelatinized starch, sodium lauryl sulfate, and titanium dioxide.
HYDRALAZINE HYDROCHLORIDEClinical Pharmacology
Although the precise mechanism of action of hydrALAZINE is not fully understood, the major effects are on the cardiovascular system. HydrALAZINE apparently lowers blood pressure by exerting a peripheral vasodilating effect through a direct relaxation of vascular smooth muscle. HydrALAZINE, by altering cellular calcium metabolism, interferes with the calcium movements within the vascular smooth muscle that are responsible for initiating or maintaining the contractile state.
The peripheral vasodilating effect of hydrALAZINE results in decreased arterial blood pressure (diastolic more than systolic); decreased peripheral vascular resistance; and an increased heart rate, stroke volume, and cardiac output. The preferential dilatation of arterioles, as compared to veins, minimizes postural hypotension and promotes the increase in cardiac output. HydrALAZINE usually increases renin activity in plasma, presumably as a result of increased secretion of renin by the renal juxtaglomerular cells in response to reflex sympathetic discharge. This increase in renin activity leads to the production of angiotensin II, which then causes stimulation of aldosterone and consequent sodium reabsorption. HydrALAZINE also maintains or increases renal and cerebral blood flow.
HydrALAZINE is rapidly absorbed after oral administration, and peak plasma levels are reached at 1 to 2 hours. Plasma levels of apparent hydrALAZINE decline with a half-life of 3 to 7 hours. Binding to human plasma protein is 87%. Plasma levels of hydrALAZINE vary widely among individuals. HydrALAZINE is subject to polymorphic acetylation; slow acetylators generally have higher plasma levels of hydrALAZINE and require lower doses to maintain control of blood pressure. HydrALAZINE undergoes extensive hepatic metabolism; it is excreted mainly in the form of metabolites in the urine.
How Supplied / Storage and Handling
HydrALAZINE Hydrochloride Tablets, USP
10 mg - round, convex, pink film-coated tablet engraved with HP above 1 on one side and plain on the other side.
Bottle of 120 tablets, NDC 62135-579-12
25 mg - round, convex, pink film-coated tablet engraved with HP above 2 on one side and plain on the other side.
Bottle of 120 tablets, NDC 62135-580-12
50 mg - round, convex, pink film-coated tablet engraved with HP above 3 on one side and plain on the other side.
Bottle of 120 tablets, NDC 62135-581-12
100 mg - round, convex, pink film-coated tablet engraved with HP above 4 on one side and plain on the other side.
Bottle of 120 tablets, NDC 62135-582-12
Dispense in a tight, light-resistant container as defined in the USP.
Store at 20° to 25°C (68° to 77°F) [See USP Controlled Room Temperature].
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
Manufactured for:
Chartwell RX, LLC.
Congers, NY 10920
Revised: 04/2023
L71441