see also: > [!info] > Category: `=this.Category` > - peripheral vasodilator. causes relaxation of arteriolar smooth muscle → lower BP - predominantly direct vasodilation of arterioles - ​reduces diastolic pressure more than systolic pressures **Onset:** - 5-20 minutes - maximum effect is 10-80 minutes **half-life:** - duration is 2-6 hours with peak effect btwn 30-60 min **Key issues:** - tachycardia → may need beta blocker - palpitations - flushing - headache - sodium/fluid retention → oedema - crosses placenta → fetal arrhymythias - **uses:** - drug of choice for women with asthma or congestive heart failure # Dose ## HTN/eclampsia in pregnancy (if not asthma or CHF, consider [[labetalol]] instead - bolus infusion *1mg/min for 10 minutes* - then titrate infusion to stabilise blood pressure by adjusting IV infusion between 1-10 mg/hour to maintain diastolic BP of 90-100 ## Children 0.1-0.2 mg/kg (max 10mg) over 5-20 min followed by infusion 4-6 mcg/kg/min max 300 mcg/min