Dosing and uses of methyldopa (Aldomet)
Adult dosage forms and strengths
injectable solution
- 50mg/mL
tablet
- 250mg
- 500mg
Hypertension
Initial: 250 mg PO q8-12hr for 2 days, increase q2Days PRn
Maintenance: 250-1000 mg/day divided q6-12hr PO, usually no more than 3 g/day
IV (methyldopate): 250-1000 mg infusion over 30-60 minutes q6-8hr PRN; no more than 4 g/day
Hypertensive Crisis
20-40 mg/kg/day divided IV q6hr
No more than 65 mg/kg/day or 3 g/day (whichever is less)
Renal Impairment
Adjust dosage frequency with renal impairment
CrCl >50 mL/min: q8hr
CrCl 10-50 mL/min: q8-12hr
CrCl <10 mL/min: q12-24hr
Administration
May increase dose/give higher amount HS to avoid adverse events during waking hours
Pediatric dosage forms and strengths
injectable solution
- 50mg/mL
tablet
- 250mg
- 500mg
Hypertension
Neonate: 2.5-5 mg/kg PO or IV q8hr
10 mg/kg/day divided q12hr PO, increase q2Days PRn
Hypertensive Crisis
20-40 mg/kg/day IV divided q6hr
No more than 65 mg/kg/day or 3 g/day (whichever is less)
Administration
May increase dose/give higher amount HS to avoid adverse events during waking hours
Geriatric dosage forms and strengths
Adverse CNS effects; may cause bradycardia and orthostatic hypotension; not recommended as routine treatment for hypertension (Beers criteria)
Not drug of choice in elderly because of CNS effects
Monitor renal function; renally excreted; decreased renal function more likely in elderly
Hypertension
Lower initial doses and more gradual adjustments recommended
125 mg qDay or q12hr; may increase by 125 mg-increments q2-3days PRn
methyldopa (Aldomet) adverse (side) effects
Frequency not defined
Angina
Bradycardia
Orthostatic hypotension
Depression
Dizziness
Lethargy
Sedation
Rash
Gynecomastia
Impotence
Dry mouth
Nausea
Vomiting
Hemolytic anemia
Thrombocytopenia
Liver toxicity
Arthralgia
Autoimmune disease
Lupus-like syndrome
Warnings
Contraindications
Active liver disease, liver disorders associated with previous methyldopa treatment
Hypersensitivity to methyldopa or other ingredients (eg, sulfites)
Pheochromocytoma
Concomitant MAOIs
Cautions
CHF, dialysis patients (increased risk of hypertension following procedure), edema, hemolytic anemia, hypotension, severe bilateral CVD, history of liver disease
Avoid abrupt withdrawaL
Risk of decreased libido and impotence in men
May impair ability to perform hazardous tasks
Tolerance develops on prolonged treatment, especially if no concurrent diuretic (methyldopa causes Na and water retention)
Interferes with some lab tests
IM/SC NOT recommended due to erratic absorption
Pregnancy and lactation
Pregnancy category: B
Lactation: distributed in breast milk but not in clinically significant amounts; compatible w/ breastfeeding
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of methyldopa (Aldomet)
Mechanism of action
Methyldopa may lower blood pressure by stimulating central inhibitory alpha-adrenergic receptors, false neurotransmission, and/or reduction of plasma renin activity.
Pharmacokinetics
Onset: PO 3-6 hr; IV 4-6 hr
Duration: PO 12-24 hr; IV 10-16 hr
Absorption: 50%
Protein Bound: MinimaL
Vd: 0.6 L/kg
Metabolism: Liver
Metabolite: Methyldopa-o-sulfate (may be active), 3-methoxy-methyldopa (inactive)
Excretion: Urine (70%), feces (30-50%)
Dialyzable: Yes (HD; removes 60%; PD removes lesser amount)
Administration
IV Incompatibilities
Additive: ampho B, methohexitaL
IV Compatibilities
Solution: D5W, NS, Ringer's, D5/Ns
Additive: aminophylline, ascorbic acid, chloramphenicol, diphenhydramine, heparin, MgSO4, netilmicin, KCl, promazine, NaHCO3, succinylcholine, verapamil, vitamin B/C
Y-site: esmolol, heparin, meperidine, morphine SO4, theophylline
IV Preparation
Dilute required dose in 100 mL D5W
IV Administration
Slow infusion over 30-60 min
