Dosing and uses of Hydralazine
Adult dosage forms and strengths
injectable solution
- 20mg/mL
tablets
- 10mg
- 25mg
- 50mg
- 100mg
Severe Essential Hypertension
10 mg PO q6hr for 2-4 days; 25 mg q6hr daily for the first week; increase to 50 mg q6hr from second week on; adjust dose to lowest effective levels
20-40 mg IM/IV; repeat as necessary
Dosing considerations
- Change to oral therapy as soon as possible
Hypertension (Chronic)
Initial: 10 mg PO q6hr for 2-4 days; may increase gradually by 10-25 mg/dose every 2-5 days up to 50 mg PO q6hr (some patients require 300 mg/day)
See also combo with isosorbide dinitrate
Hypertensive Crisis
20-40 mg IV/IM; repeat PRn
Pregnancy-associated
- 5-10 mg IV/IM initially, THEN 5-10 mg q20-30min PRN, OR
- 0.5-10 mg/hr IV infusion
Congestive Heart Failure
Initial dose: 10-25 mg q6-8hr PO
Maintenance dose: 225-300 mg/day divided q6-8hr PO
Dosing considerations
- Adjust dose per individual response
Pediatric dosage forms and strengths
injectable solution
- 20mg/mL
tablets
- 10mg
- 25mg
- 50mg
- 100mg
Severe Essential Hypertension
1.7-3.5 mg/kg/day IM or IV divided in 4-6 doses.
Hypertensive Crisis
3 months - 1 year: 0.1-0.5 mg/kd/dose IV q6-8hr; not to excced 2 mg/kg IV q6hr; titrate dose for blood pressure controL
>1 year: 0.1-0.2 mg/kg IV/IM q4-6hr PRN initially; may increase to usual dose of 1.7-3.5 mg/kg/day divided q4-6hr; not to exceed 20 mg/dose IM or IV or 2 mg/kg q3-6hr with cumulative dose not to exceed 9 mg/kg
Hypertension (Chronic)
Initial: 0.75-1 mg/kg/day PO divided q6-12hr
Maximum dose in infants (<1 year): 5 mg/kg/day PO divided q6-12hr, 20 mg/dose, or 200 mg/day
Maximum dose in children (>1 year): 7.5 mg/kg/day PO divided q6hr; not to exceed 200 mg/day
Increase gradually over 3-4 weeks
Hydralazine adverse (side) effects
Frequency not defined
Hypotension
Palpitations
Conjunctivitis
Tachycardia
Headache
Peripheral edema
Vascular collapse
Peripheral neuropathy
Anorexia
Diarrhea
Nausea
Vomiting
Psychotic reaction
Agranulocytosis
Leukopenia
Hepatotoxicity
Chest pain
Dyspnea
Nasal congestion
Paralytic ileus
Dysurea
Thrombocytopenia
Peripheral neuritis
Rheumatoid arthritis
Agranulocytosis
Arthralgia
SLE syndrome
Warnings
Contraindications
Hypersensitivity to hydralazine
Coronary artery disease
Mitral valve rheumatic heart disease
Cautions
May induce SLE-type syndrome (usually at >200 mg/day); instruct patients to report joint/chest pain or fever; consider discontinuation if occurs
Use caution in CVA, severe renal impairment, volume depletion, preexisting hypotension, concurrency with other hypotensive agents, CAD (potential contraindication)
Discontinue slowly to avoid rapid rise in blood pressure
Use with caution in patients with pulmonary hypertension; may cause hypotension
Increases fluid and sodium retention; may require treatment or increase in diutretic dose
Peripheral neuritis reported; treat symptoms with pyridoxine
Pregnancy and lactation
Pregnancy category: C
Lactation: Excreted in breast milk; use caution
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Hydralazine
Mechanism of action
Direct vasodilator; dilates arterioles with little effect on vein; decreases systemic resistance, which subsequently decreases blood pressure.
Absorption
Bioavailability: Slow acetylator: 30-50%; rapid acetylator: 22-30%
Onset: 5-20 min, maximum effect 10-80 min (IV); 20-30 min (PO)
Duration: 3-8 hr (PO); 1-4 hr (IV)
Distribution
Protein bound: 85-90%
Vd: 0.3-8.2 L/kg
Metabolism
Significantly metabolized in liver by acetylation; slow and rapid acetylator
Metabolites: Phthalazine and pyruvic acid hydrazone metabolites (inactive metabolite)
Elimination
Half-life: 2-8 hr (normal renal function); 7-16 hr (end-stage renal disease)
Excretion: Urine (14%; unchanged)
Pharmacogenomics
HLA-DRw4 appears in 73% of patients experiencing hydralazine-associated SLe
Administration
IV Incompatibilities
Solution: D5W, D10/LR, fructose 10%, fructose 10%/Ns
Additive: Aminophylline, ampicillin, chlorothiazide, dobutamine, CaNa2EDTA, ethacrynate, hydrocortisone sodium succinate, mephentermine, methohexital, nitroglycerin, phenobarbital, verapamiL
Y-site: Aminophylline, ampicillin, diazoxide, furosemide
IV Compatibilities
Solution: Dextrose-Ringer combinations, D5/LR, dextrose 2.5%/½LR, dextrose-saline combinations, D10W, Ringer, LR, ½NS, NS, Na-lactate 1/6m
Y-site: Heparin, hydrocortisone sodium succinate, nitroglycerin (compatible for 3 hr; may form slight ppt), KCl, verapamil, vit B/C
IV Preparation
Prepare immediately before use
Minimize contact with metal parts during preparation and administration
IV/IM Administration
Administer IM or as rapid IV injection directly into vein
Avoid adding drug to infusion solution
Storage
Store at controlled room temp
Do not refrigerate
