Disclaimer to the On-line Edition
This Manual has been designed for use in the NICU at London Health Sciences Centre (LHSC), London, Ontario, Canada, and represents clinical practice at this institution. The information contained within the Manual may not be applicable to other centres. If users of this Manual are not familiar with a drug, it is recommended that the official monograph be consulted before it is prescribed and administered. Any user of this information is advised that the contributors, Editor and LHSC are not responsible for any errors or omissions, and / or any consequences arising from the use of the information in this Manual.



  • treatment of hypertension - but not the drug of choice for treatment of acute hypertensive crisis, see Diazoxide
  • an afterload reducing agent to treat congestive heart failure


  • causes direct relaxation of smooth muscle in peripheral vasculature; coronary, cerebral, splanchnic and renal vessels are affected more than vessels in muscle or skin
  • undergoes high first pass effect when given orally
  • approximately 85% is protein bound
  • less than 15% of a given dose is excreted unchanged in the urine; dosage adjustments do not appear to be necessary in renal failure
  • an increase in heart rate and cardiac output occur after hydralazine administration. This is in response to the decrease in peripheral vascular resistance

Side Effects

  • cardiovascular (reflex tachycardia, hypotension)
  • GI (vomiting, diarrhea, irritation and bleeding)
  • a lupus-like syndrome has been reported in 10-20% of adult patients
  • tachyphylaxis (decrease in response) can occur with prolonged therapy


  • IV: 0.1 to 0.5 mg/kg every 3 to 6 h IV push by physician only, over at least 1 minute
  • dilute to at least 1 mg/mL with 0.9% NaCl when giving IV
  • when changing from IV to oral therapy, an increase of up to twice the effective IV dose may be necessary
  • PO: 0.2 to 1 mg/kg every 3 to 6h


  • 1 mg/mL diluted solution (0.9% NaCl) for IV use, in a vial, prepared by Pharmacy. Stable for 24 hours. DO NOT REFRIGERATE.
  • 1 mg/mL oral solution prepared by Pharmacy
  • 20 mg/mL, 1mL ampoule - after hours use


  1. McEvoy G K (ed): AHFS Drug Information, American Society of Hospital Pharmacists, 1991.
  2. Roberts, RJ: Drug Therapy in Infants, W.B. Saunders, Toronto, 1984.
  3. Trissel L.A.: Handbook on Injectable Drugs, American Society of Hospital Pharmacists 1988.
  4. Pagliaro LA and Pagliaro AM (ed): Problems in Pediatric Drug Therapy, 1987, Drug Intelligence Publ Inc, Hamilton, Illinois.
  5. Parenteral Drug Administration Guidelines, St. Joseph's Health Centre, London, Ontario.
  6. Gomella TL (Ed): Neonatology - Management, Procedures, On-Call Problems, Diseases, Drugs, 1992, Appleton and Lange, Norwalk, Connecticut.
  7. Milan EM and McFeely EJ: Memory Bank for Neonatal Drugs, 1990, Williams and Wilkins, Baltimore.
  8. Young TE and Mangum OB: Neofax - A Manual of Drugs Used in Neonatal Care, Columbus, Ohio: Ross Laboratories, 1992.

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