Table 15. Intravenous or intramuscular anti-hypertensive drugs for hypertensive emergencies.

Drug name	Dosage	Onset time	Duration	Side effects
Nitroprusside	The intravenous infusion dose stars from 6.25–12.5 µg/min and adjusts it according to blood pressure (perioperative hypertension). 0.25–10 µg/kg per minute, IV (hypertension emergencies) Initial dose: 0.3–0.5 g/kg per minute. The dose can be gradually increased according to the blood pressure response; the maximum dose is 10 g/kg per minute (pregnancy-induced hypertension; safety level: C).	Immediately	2–10 min	Hypotension, tachycardia, headache, muscle spasms. Continuous use for more than 48 to 72 h or administration doses > 2 g/kg per minute may induce cyanide poisoning.
Nitroglycerine	5–100 µg/min, IV (hypertensive emergency with myocardial ischemia).	2–5 min	5–10 min	Headache and vomiting.
Phentolamine	2.5–5 mg, IV (used to diagnose pheochromocytoma and to treat hypertensive episodes caused by it, including hypertension occurred during surgical resection, and can also be used to assist in the diagnosis of pheochromocytoma based on the BP response to it).	1–2 min	10–30 min	Tachycardia, headache and flushing.
Nicardipine	0.5–10 µg/kg per minute, IV, (perioperative hypertension, hypertension emergencies). The initial dose is 5 mg/h, and is gradually increased to 15 mg/h according to blood pressure response (pregnancy-induced hypertension, safety level C).	5–10 min	1–4 h	Tachycardia, headache, peripheral edema, angina pectoris, nausea, dizziness, inhibition of uterine contraction (combined with magnesium sulfate).
Esmolol	0.15–0.3 mg/kg per minute, IVI (perioperative hypertension). 250–500 µg/kg, IV Followed by 50–300 µg/kg per minute, IV, (hypertension emergencies).	1–2 min	10–20 min	Hypotension and nausea.
Metoprolol	3–5 mg, IV, repeated every 5 min, the maximum dose is 15 mg (hypertension emergencies).	5–10 min	5–10 h	Hypotension, heart failure, heart block, dizziness, fatigue, depression, bronchospasm.
Labetalol	25–50 mg, IV, repeat every 15min is permitted, and the total dose can be used up to 200 mg. Intravenous infusion is also feasible, 1–4 mg/min, IV (perioperative hypertension). 20–80 mg IV, 0.5–2.0 mg/min IVI (hypertensive emergency).	5–10 min	3–6 min	Nausea, vomiting, cephalic anesthesia, bronchospasm, conduction block, orthostatic hypotension.
Urapidil	10–50 mg IV 6–24 mg/h	5 min	2–8 h	Hypotension, dizziness, nausea, and fatigue.
Enalaprilat	1.25–5 mg IV q6 h	15–30 min	6–12 h	Blood pressure has a steep drop in high renin status, and the variation is high.
Diltiazem	5–10 mg IV, or 5–15 µg/kg per minute IVI (perioperative hypertension, hypertension emergencies).	5 min	30 min	Tachycardia, AV block, hypotension, cardiac failure, peripheral edema, headache, constipation, hepatotoxicity.
Dralzine	10–20 mg IV 10–40 mg IM	10–20 min 20–30 min	1–4 h 4–6 h	Tachycardia, flushing, headache, vomiting and angina aggravated.
Fenoldopam	0.03–1.6 µg/kg per minute, IV	< 5 min	30 min	Tachycardia, flushing, headache and vomiting.
Magnesium sulphate*	Dilute 5 g magnesium sulphate to 20 mL and inject slowly for 5 min, followed by 1 to 2 g/h IVI for maintenance; or dilute 5 g magnesium sulphate to 20 mL and deep intramuscular injection every 4 h. The total dosage can be used to 25–30 g/d (pregnancy-induced hypertension, severe pre-eclampsia).			The drug should be stopped when urine volume < 600 mL/day, respiration < 16 times/min and tendon reflex disappeared.

*Non-hypertensive drugs. The use of emergency anti-hypertensive drugs is detailed as per the instructions. IV: intravenous injection; IM: intramuscular injection; IVI: intravenous infusion.