Dose:  0.1 to 1.0 mg/kg/dose IV, IM, PO

Frequency: Q 3 to 6 hours

Comments: Hydralazine is an antihypertensive agent that causes direct relaxation of smooth muscle in the peripheral vascular bed. Vasodilation is not uniform, with more prominent effects seen in the coronary, cerebral, and renal vascular beds.  The major effects are to decrease systemic vascular resistance and increase cardiac output.  Because its potent vasodilation triggers activation of the sympathomimetic nervous system, combination therapy with sympatholytic agents (such as propranolol) have been recommended.  Hydralazine is not the drug of choice when treating hypertensive emergencies.  After starting treatment with hydralazine, increase the dose until the hypertension is controlled, side effects occur, or a maximum of 8 mg/kg/day is reached.  Because of decreased bioavailability following oral administration, the parenteral dose is doubled when the drug is given by this route.  Further comments on hydralazine.

Preparation:
IV:Hydralazine (Apresoline) is available in a 20 mg/ml concentration.  To prepare a 2 mg/ml solution, draw up 1 ml of the 20 mg/ml concentration into a 12 cc syringe. Using NS or other compatible diluent, draw up 9 ml in the same syringe. Agitate the solution. A 0.20 mg/ml is then prepared by repeating the above procedure  using 1 ml of the 2 mg/ml solution and mixing with 9 ml of diluent. Administer immediately after mixing.. Color changes may occur after contact with metal. Hydralazine undergoes color changes in most infusion fluids. Flush IV with compatible fluid before and after dose. Administer over 3-5 minutes. The manufacturer recommends that the drug be discarded after single use, though Tissel reports that there is no loss of potency over 12 hours though the solution may become discolored (Trissel. Pocket Guide to Injectable Drugs. American Society of Hospital Pharmacists, Inc.:Bethesda, MD. 1992:114). Store at room temperature.

IM: Give undiluted injection. Administer immediately after drawing up in syringe. Color changes may occur after contact with metal. Administer slowly. Discard after single use.

PO: Hydralazine (Apresoline) is available in a 20 mg/5 ml (4 mg/ml) concentration for oral use. It has a stability of 30 days and may be more convenient for big babies who are going home on the medication. Refigerate and shake well before use. An extemporaneous form with a concentration of 1 mg/ml can be prepared by diluting 1 ml of the 20 mg/ml IV preparation with 20 ml Sorbitol 70%. Refrigerate. Stable for 7 days. (SJMMC Small & Bulk Compounding).