Product information:
| Product name |
Methyldopa tablets |
| Specifications |
10's/10/box 250mg |
| Shelf Life |
3 Years |
| Storage |
Dry Cool Place |
| Usage |
Antihypertensive |
Pharmacology:
1. Methyldopa is an aromatic amino acid decarboxylase inhibitor.
2. Only the L-isomer of methyldopa has antihypertensive activity in humans, and racemic (DL - α - methyldopa) needs twice the dose to achieve the same antihypertensive effect. Its antihypertensive effect may be through its active metabolite methylnorepinephrine stimulating the inhibitory α - adrenoceptor and acting as a pseudo neurotransmitter to reduce plasma renin activity, thus lowering arterial blood pressure.
3. Methyldopa can reduce the concentration of 5-hydroxytryptamine, dopamine, norepinephrine and methyladrenaline in tissues.
4. Methyldopa has no direct effect on cardiac function and usually does not reduce glomerular filtration rate, renal blood flow and filtration fraction.
5. Cardiac output remains unchanged at normal heart rate, and heart rate slows down in some patients.
6. Plasma renin activity decreased during treatment.
7. Methyldopa can reduce the blood pressure in supine and orthostatic position, and postural hypotension is rarely seen. Hypotension during daytime exercise is rare.
Pharmacokinetics:
The oral absorption of methyldopa varies from 50% to less than 20% with plasma protein. The antihypertensive effect reached the peak at 4-6 hours after single oral administration, and lasted for 12-24 hours. Once the effective antihypertensive dose is reached, most people can produce stable antihypertensive effect for 12-24 hours. Blood pressure recovered 24-48 hours after drug withdrawal. The half-life of plasma was about 1.7 hours and 3.6 hours in anuria. The drug is mainly metabolized in the liver, producing a variety of metabolites, such as methylnorepinephrine. Nearly 70% of the metabolites are excreted in urine in the form of prototype and a small amount of metabolites. The renal clearance rate was about 130 ml / min in normal subjects, and decreased in renal insufficiency. 36 hours after oral administration, the body was almost completely cleared.
Indication:
Methyldopa tablets, indications for hypertension.
Adverse reactions:
1. Sedation, headache and fatigue appear more often than at the beginning of medication and dosage, usually transient.
2. more common are edema of lower limbs caused by retention of water and sodium, dry mouth.
3. Less common are: drug fever or eosinophilia, liver function changes (may be immune or allergic), mental changes (depression or anxiety, somniloquy, insomnia), decreased sexual function, diarrhea, breast enlargement, nausea, vomiting, fainting.
4. Angina pectoris and heart failure were occasionally added.
5. Rare: prolonged carotid sinus sensitivity and postural hypotension time, weight gain, sinus bradycardia, liver function damage, pancreatitis, colitis, salivary gland inflammation, tongue pain or black tongue, constipation, abdominal distension, exhaust, hyperprolactinemia, myelosuppression, thrombocytopenia, hemolytic anemia, leukopenia, antinuclear antibody, LE cells, rheumatoid factor positive , Direct antiglobulin (Coombs) test positive, myocarditis, pericarditis, vasculitis, lupus like syndrome, Parkinson's disease, tremor paralysis, slow reaction, involuntary chorea, symptoms of cerebral vascular insufficiency, mental disorder such as dreaminess, sedation, weakness, abnormal sensation, elevated urea nitrogen (BUN), joint pain, joint swelling, muscle pain, nasal congestion, epidermal necrosis, skin, etc Rash, amenorrhea, male breast development, lactation.
6. Rare: granulocytopenia, which returned to normal after withdrawal of drug; fatal hepatocyte necrosis.
Taboo:
1. Active liver diseases, such as acute hepatitis, active liver cirrhosis.
2. Coombs test was positive.
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