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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
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 pain when an area is touched or pressed. সহজ বাংলা: চাপ দিলে ব্যথা।" data-rx-term="tenderness" data-rx-definition="Tenderness means pain when an area is touched or pressed. সহজ বাংলা: চাপ দিলে ব্যথা।">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
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.
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.
References
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