What is the normal frequency for using hydralazine hcl?

Do you mean dosage? The normal dosage for adults is 0.143 to 0.357 mg/kg per 6 hours orally to start, then after many weeks 0.143 to 0.357 mg/kg per 6 hours as needed. If given iv, 5-10mg per 10-15 min to a maximum of 50mg.