Table 4: Antihypertensives in pregnancy.

Drugs Method of action (MOA) Side effects Fetal concerns Indication Dosage

(I) Sympathetic nervous system inhibitors
(A) Central acting
 (1) Methyldopa  agent of choice Alpha2 agonist. Onset is gradual (6–8 hrs)Decreased mental alertness, impaired sleep, sense of fatigue and depression, xerostomiaConsidered safe (Category B) Preferred drug for non emergent BP control 0.5–3 gm PO in 2 divided doses
 (2) Clonidine Alpha-2 agonist As aboveLimited data (Category C). Considered safe as same MOA as methyldopa Nonemergent BP controlto 0.3 mg q8–12 hrs
(B) Peripheral acting
 (1) Labetalol Beta and alpha blocker Fatigue, lethargy, exercise intolerance, sleep disturbances, and asthmaConcern for LBW infants and decrease uteroplacental blood flow though long-term data suggesting safety. Risk of neonatal hypoglycemia at higher doses (Category C) Nonemergent and emergent Bp control 20–1200 mg in 2-3 divided doses. 10–20 mg IV then 20–80 mg IV every 20–30 minutes, maximum of 300 mg: for infusion 1-2 mg/min

(II) Calcium channel blockers
(A) NifedipineCalcium channel blocker DihydropyridineTachycardia, palpitations, peripheral edema, headache, and facial flushingDoes not cause decrease maternal blood flow. Concern regarding concomitant uses with magnesium though not proven in recent evaluations (Category C)Non-emergent and emergent BP control30–120 mg extended release preparations

(III) Direct vasodilators
(A) HydralazineSelectively relaxes arteriolar smooth muscle by an unknown mechanismAcutely: Headache, nausea, flushing, palpitations. Chronic use: Pyridoxine-responsive polyneuropathy or immunologic reaction like drug induced lupusEffect on uteroplacental blood flow is uncertain. Associated with more maternal and perinatal adverse events than other agents when used acutely. Neonatal thrombocytopenia and Lupus have been reported. Not proven to be teratogenicUseful in combination with sympatholytic agents. Used for emergent and nonemergent BP control50–300 PO mg in 2–4 divided doses. 5 mg IV, then 5–10 mg every 20–40 min: once BP controlled repeat every 3 hours. For infusion: 0.5 to 10 mg/hr
(B) Sodium nitroprusside
Relatively contraindicated. Considered as a last resortDirect NO inhibitor Non-selectively relaxes arteriolar and venular vascular smooth musclesExcessive vasodilation and cardioneurogenic syncope in volume depleted patients. Cyanide toxicity if used greater than 4 hours. Labor arrest hyperglycemiaRisk of fetal cyanide intoxication remains unknownOnly for emergent Bp control as last resort30–50 mg IV every 5–15 minutes Infusion at 0.25–5.0 mcg/kg/min
(IV) Diuretics
(A) Hydrochlorothiazide Thiazide diuretics. Blocks Na channels in distal-convoluted tubules Volume contraction and electrolyte disturbances. Hyperuricemia Volume contraction may limit fetal growth, though not proven in studies Nonemergent BP control 12.5–25 mg/day

(V) ACE-I and ARB
Contraindicated in pregnancy. Should be discontinued prior to conception ACE-I: inhibits angiotensin-converting enzyme interfering with conversion of angiotensin I to angiotensin II ARB: antagonizes ATI receptor Angioedema, hypotension, hyperkalemia, renal failure. Cough (only in ACE-I)ACE-I: renal dysgenesis, oligohydramnios, calvarial and pulmonary hypoplasia, IUGR. Neonatal anuric renal failure, fetal death Arbs: same concerns Not indicated N/A