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| 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, xerostomia | Considered 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 above | Limited data (Category C). Considered safe as same MOA as methyldopa | Nonemergent BP control | to 0.3 mg q8–12 hrs |
| (B) Peripheral acting | | | | | |
| (1) Labetalol | Beta and alpha blocker | Fatigue, lethargy, exercise intolerance, sleep disturbances, and asthma | Concern 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) Nifedipine | Calcium channel blocker Dihydropyridine | Tachycardia, palpitations, peripheral edema, headache, and facial flushing | Does 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 control | 30–120 mg extended release preparations |
|
| (III) Direct vasodilators | | | | | |
| (A) Hydralazine | Selectively relaxes arteriolar smooth muscle by an unknown mechanism | Acutely: Headache, nausea, flushing, palpitations. Chronic use: Pyridoxine-responsive polyneuropathy or immunologic reaction like drug induced lupus | Effect 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 teratogenic | Useful in combination with sympatholytic agents. Used for emergent and nonemergent BP control | 50–300 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 resort | Direct NO inhibitor Non-selectively relaxes arteriolar and venular vascular smooth muscles | Excessive vasodilation and cardioneurogenic syncope in volume depleted patients. Cyanide toxicity if used greater than 4 hours. Labor arrest hyperglycemia | Risk of fetal cyanide intoxication remains unknown | Only for emergent Bp control as last resort | 30–50 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 |
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