Hydralazine

Hydralazine

[$5.18 per ampoule IV]

ADMINISTRATION ROUTES:

• IV, PO

ALTERNATIVE NAMES:

• Apresoline

ICU INDICATIONS:

1. afterload reduction/ peripheral vasodilation

PRESENTATION AND ADMINISTRATION:

• IV:
  20mg ampoules of powder
  Reconstitute with 1ml of water for injection
  For direct injection, inject as either reconstituted solution or further dilute with a small volume of normal saline. Give over 1-2 minutes For IV infusion reconstitute 100mg and add to 100ml of compatible IV fluid
  Compatible with the following IV fluids:
  Normal saline, Hartmanns
  Note: 5% dextrose should not be used as glucose rapidly causes hydralazine to be broken down.
  Prepare solutions immediately before use and discard after 24 hours.
  Hydralazine undergoes colour changes in most infusion fluids; however, these changes generally do not indicate loss of potency.
  Store at room temperature.

• PO:
  Rarely indicated in ICU

DOSAGE:

• IV:
  5mg IV stat, then up to 20mg per hour by infusion.

DOSAGE IN RENAL FAILURE AND RENAL REPLACEMENT THERAPY:

• Start with a small dose and adjust in accordance with response

DOSAGE IN PAEDIATRICS:

• IV:
  0.1-0.2mg/kg stat, then 4-6mcg/kg/min

CLINICAL 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

CONTRAINDICATIONS:

1. Hypersensitivity to hydralazine

WARNINGS

• In a few patients hydralazine may produce a clinical picture simulating systemic lupus erythematosus including glomerulonephritis. In such patients hydralazine should be discontinued unless the benefit-to-risk determination requires continued antihypertensive therapy with this drug.

PRECAUTIONS

• General:
  Myocardial stimulation produced by hydralazine can cause anginal attacks and ECG changes of myocardial ischemia. The drug has been implicated in the production of myocardial infarction. It must, therefore, be used with caution in patients with suspected coronary artery disease
• Peripheral neuritis, evidenced by paresthesia, numbness, and tingling, has been observed.
• Laboratory Tests:
  No tests in addition to routine ICU tests are required
• Drug/Laboratory Test Interactions:
  None known

IMPORTANT DRUG INTERACTIONS FOR THE ICU

• Concomitant administration with other antihypertensives increases the risk of hypotension

ADVERSE REACTIONS

• Body as a Whole:
  Rash, urticaria, pruritus, fever, chills
• Cardiovascular System:
  Hypotension, paradoxical pressor response, oedema, palpitations, tachycardia, angina pectoris Respiratory System: Dyspnea.
• Gastrointestinal System:
  Constipation, paralytic ileus, anorexia, vomiting, diarrhoea,
• Haematological System:
  Blood dyscrasias, consisting of reduction in haemoglobin and red cell count, leukopenia, agranulocytosis, purpura; lymphadenopathy; splenomegaly.
• Neurological System:
  Headache, peripheral neuritis, evidenced by paresthesia, numbness, and tingling; dizziness; tremors; muscle cramps; psychotic reactions characterized by depression, disorientation, or anxiety.