illnesshacker: Medical information and health advice you can trust.

Alpha Methyldopa; Indications/Uses, Dosage, Side effects, Interaction ,Pregnancy

Methyldopa is a phenylalanine derivative and an aromatic amino acid decarboxylase inhibitor with antihypertensive activity. Methyldopa is an alpha-2 adrenergic agonist that has both central and peripheral nervous system effects. Its primary clinical use is as an antihypertensive agent. Methyldopa is a prodrug and is metabolized in the central nervous system. The antihypertensive action of methyldopa seems to be attributable to its conversion into alpha-methylnorepinephrine, which is a potent alpha-2 adrenergic agonist that binds to and stimulates potent central inhibitory alpha-2 adrenergic receptors. This results in a decrease in sympathetic outflow and decreased blood pressure.

Methyldopa is a medication used for high blood pressure. It is one of the preferred treatments for high blood pressure in pregnancy. For other types of high blood pressure including very high blood pressure resulting in symptoms other medications are typically preferred. It can be given by mouth or by injection into a vein. The onset of effects is around 5 hours and them last about a day.

Mechanism of Action of Alpha Methyldopa

Although the mechanism of action has yet to be conclusively demonstrated, the resultant hypotensive effect is most likely due to the drug’s action on the CNS. Methyldopa is converted into the metabolite, alpha-methylnorepinephrine, in the CNS, where it stimulates the central inhibitory alpha-adrenergic receptors, leading to a reduction in sympathetic tone, total peripheral resistance, and blood pressure. Reduction in plasma renin activity, as well as the inhibition of both central and peripheral norepinephrine and serotonin production, may also contribute to the drug’s antihypertensive effect, although this is not a major mechanism of action. This is done through the inhibition of the decarboxylation of dihydroxyphenylalanine (dopa)—the precursor of norepinephrine—and of 5-hydroxytryptophan (5-HTP)—the precursor of serotonin—in the CNS and in most peripheral tissues.

Indications of Alpha Methyldopa

High Blood Pressure (Hypertension)
Hypertensive crisis
Gestational hypertension (or pregnancy-induced hypertension) and pre-eclampsia
Hypertensive Emergency

You Might Also Like Vitamin D - Types, Symptoms, Food Source, Health Benefit

Contra-Indications of Alpha Methyldopa

Pheochromocytoma
Porphyria
Destruction of red blood cells by body’s own antibodies
Anemia
Depression
Parkinson Symptoms
Angina
Chronic heart failure
Severe disorder of the blood vessels of the brain
Hardening of the liver
Liver problems
Severe liver disease
Kidney disease with a reduction in kidney function
Visible Water Retention

The dosage of Alpha Methyldopa

Strengths: 250 mg; 500 mg; 125 mg; 50 mg/mL, 250 mg/5 mL

Hypertension

Initial dose: 250 mg orally 2-3 times a day or 250 to 500 mg IV over 30 to 60 minutes every 6 hours, up to a maximum of 3 g/day.
Maintenance dose: 500 mg to 2 g orally divided in 2 to 4 doses, up to a maximum of 3 g/day.

Hypertensive Emergency

250 to 500 mg IV over 30 to 60 minutes every 6 hours up to a maximum of 1 g every 6 hours or 4 g/day. Switch to the oral route at the same dosage once blood pressure is under control.

Side Effects of Alpha Methyldopa

The most common

Depression or even suicidal ideation, as well as nightmares
Anxiety, especially of the social anxiety variant
Xerostomia or dry mouth
Gastrointestinal disturbances such as diarrhea or constipation
Headache or migraine
Myalgia or muscle aches, arthralgia or joint pain, or paresthesia (“pins and needles”)
Restless legs syndrome (RLS)
Decreased alertness, awareness, and wakefulness
Impaired attention,
Decreased desire, and motivation
Fatigue or lassitude
Sedation or drowsiness or somnolence or sleepiness
Agitation or restlessness
Cognitive and memory impairment

More common

Abdominal or stomach pain, discomfort, or tenderness
chills or fever
difficulty with moving
headache, severe and throbbing
joint or back pain
muscle aching or cramping
muscle pains or stiffness
chest pressure or squeezing pain in chest
discomfort in arms, shoulders, neck or upper back
excessive sweating
feeling of heaviness, pain, warmth and/or swelling in a leg or in the pelvis
sudden tingling or coldness in an arm or leg
sudden slow or difficult speech
sudden drowsiness or need to sleep
fast breathing
sharp pain when taking a deep breath
fast or slow heartbeat
coughing up blood
rust colored urine
decreased amount of urine

You Might Also Like What Is Silver Sulfadiazine? - Uses, Dosage, Side Effects

Rare

Anxiety
change in vision
chest pain or tightness
confusion
cough
Agitation
arm, back, or jaw pain
blurred vision
chest pain or discomfort
convulsions
extra heartbeats
fainting
hallucinations
headache
irritability
lightheadedness
mood or mental changes
muscle pain or cramps
muscle spasm or jerking of all extremities
nervousness

Drug Interactions of Alpha Methyldopa

Alpha-methyldopa may interact with following drug, supplements, & may change the efficacy of the drug

alpha-1 blockers (e.g., doxazosin, prazosin, tamsulosin)
alpha-2 blockers (e.g., clonidine, dexmedetomidine, methyldopa)
angiotensin-converting enzyme inhibitors (ACEIs; e.g., captopril, ramipril)
angiotensin II receptor blockers (i.e., irbesartan, losartan, valsartan)
antipsychotics (e.g., clozapine, olanzapine, quetiapine, risperidone)
atorvastatin
azole antifungals (e.g., itraconazole, ketoconazole, posaconazole)
barbiturates (e.g., phenobarbital)
benzodiazepines (e.g., alprazolam, diazepam, lorazepam)
beta-agonists (e.g., formoterol, salbutamol, salmeterol)
other beta-blockers (e.g., propranolol, metoprolol)
calcium channel blockers (e.g., amlodipine, diltiazem, nifedipine, verapamil)
carbamazepine
cyclosporine
dexamethasone
diuretics (water pills; e.g., furosemide, hydrochlorothiazide)
duloxetine
levodopa
lidocaine
MAO inhibitors (e.g., phenelzine, moclobemide, selegiline)
macrolide antibiotics (e.g., azithromycin, clarithromycin, erythromycin)
nilotinib
nonsteroidal anti-inflammatory drugs (NSAIDs; e.g., ibuprofen, naproxen)
other beta-blockers (e.g., atenolol, metoprolol, propranolol)
pentoxifylline
phosphodiesterase-5-inhibitors (e.g., sildenafil, tadalafil)
selective serotonin reuptake inhibitors (SSRI; e.g., fluoxetine, paroxetine, sertraline)
sunitinib
theophyllines (e.g., aminophylline, oxtriphylline, theophylline)

Pregnancy Catagory of Alpha Methyldopa

FDA Pregnancy Category B

Pregnancy

Methyldopa crosses the placenta, and may cause mild hypotension in neonates of treated mothers. Because it has been safely and successfully used to treat hypertension during pregnancy, some experts consider it to be the drug of choice for the treatment of nonemergent hypertension during pregnancy.

You Might Also Like Tacrolimus Anhydrous - Uses, Dosage, Side Effects

Lactation

Because of the low levels of methyldopa in breastmilk, amounts ingested by the infant are small and would not be expected to cause any adverse effects in breastfed infants. No special precautions are required.