Description

Simple

A medication used to treat high blood pressure.

Clinical

An alpha-2 adrenergic agonist used to treat hypertension.

Overview

An alpha-2 adrenergic agonist that has both central and peripheral nervous system effects. Its primary clinical use is as an antihypertensive agent. [PubChem]

Pharmacology

Indication

For use in the treatment of hypertension.

Pharmacodynamic

Methyldopa is an aromatic-amino-acid decarboxylase inhibitor in animals and in man. Only methyldopa, the L-isomer of alpha-methyldopa, has the ability to inhibit dopa decarboxylase and to deplete animal tissues of norepinephrine. In man the antihypertensive activity appears to be due solely t... Read more

Mechanism of action

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-adrener... Read more

Absorption

Absorption from the gastrointestinal tract is variable but averages approximately 50%.

Protein binding

Low (less than 20%).

Volume of distribution

Information currently not available.

Clearance

Renal cl=130 mL/min [healthy]

Half life

The plasma half-life of methyldopa is 105 minutes.

Route of elimination

Methyldopa is extensively metabolized. The known urinary metabolites are: α-methyldopa mono-O-sulfate; 3-0-methyl-α-methyldopa; 3,4-dihydroxyphenylacetone; α-methyldopamine; 3-0-methyl-α-methyldopamine and their conjugates. Approximately 70 percent of the drug which is absorbed is excreted in the ur... Read more

Toxicity

The oral LD50 of methyldopa is greater than 1.5 g/kg in both the mouse and the rat. Symptoms of overdose include bloating, constipation, diarrhea, dizziness, extreme drowsiness, gas, light-headedness, nausea, severely low blood pressure, slow heartbeat, vomiting, and weakness.

Adverse Effects

Contraindications

  • Route:
    • Oral
    • Intravenous
  • Regions: US
  • With Categories Coadmin:
      • Name: Monoamine Oxidase Inhibitors
      • Drugbank Id: DBCAT001004
      • Mesh Id: D008996
  • Route:
    • Oral
    • Intravenous
  • Regions: US
  • Patient Conditions:
      • Name: Active hepatic disease
      • Drugbank Id: DBCOND0108088
      • Modification Of:
        • Condition Status: active
        • Base:
          • Name: Hepatic Disease
          • Drugbank Id: DBCOND0069929
  • Route:
    • Oral
    • Intravenous
  • Regions: US
  • Patient Conditions:
      • Name: History of liver disorders caused by methyldopa
      • Drugbank Id: DBCOND0108091
      • Combination Of:
        • Caused By:
            • Name: Methyldopa
            • Drugbank Id: DBCOND0108090
        • Included Conditions:
            • Name: History of liver disorders
            • Drugbank Id: DBCOND0108089

Food Interactions

  • Administer vitamin supplements.
  • Avoid alcohol.
  • Avoid natural licorice.
  • Take with or without food. The absorption is unaffected by food.

Interactions

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  • Paracetamol(acetaminophen)
  • Paxil(paroxetine)
  • Pamelor(nortriptyline)
  • Panadol(acetaminophen)
  • Patanol(olopatadine ophthalmic)
  • Pataday(olopatadine ophthalmic)
  • Parnate(tranylcypromine)
  • Pazeo(olopatadine ophthalmic)
1-benzylimidazole
1-benzylimidazole may decrease the antihypertensive activities of Methyldopa.
2,5-Dimethoxy-4-ethylamphetamine
2,5-Dimethoxy-4-ethylamphetamine may decrease the antihypertensive activities of Methyldopa.
2,5-Dimethoxy-4-ethylthioamphetamine
2,5-Dimethoxy-4-ethylthioamphetamine may decrease the antihypertensive activities of Methyldopa.
3,5-Dinitrocatechol
The metabolism of Methyldopa can be decreased when combined with 3,5-Dinitrocatechol.
4-Bromo-2,5-dimethoxyamphetamine
4-Bromo-2,5-dimethoxyamphetamine may decrease the antihypertensive activities of Methyldopa.
4-Methoxyamphetamine
4-Methoxyamphetamine may decrease the antihypertensive activities of Methyldopa.
5-methoxy-N,N-dimethyltryptamine
5-methoxy-N,N-dimethyltryptamine may decrease the antihypertensive activities of Methyldopa.
7,8-Dichloro-1,2,3,4-tetrahydroisoquinoline
7,8-Dichloro-1,2,3,4-tetrahydroisoquinoline may decrease the hypotensive activities of Methyldopa.
Abacavir
Methyldopa may decrease the excretion rate of Abacavir which could result in a higher serum level.
Abediterol
Abediterol may decrease the antihypertensive activities of Methyldopa.
Acarbose
Acarbose may decrease the excretion rate of Methyldopa which could result in a higher serum level.
Acebutolol
The therapeutic efficacy of Methyldopa can be decreased when used in combination with Acebutolol.
Aceclofenac
The therapeutic efficacy of Methyldopa can be decreased when used in combination with Aceclofenac.
Acemetacin
The therapeutic efficacy of Methyldopa can be decreased when used in combination with Acemetacin.
Acepromazine
The therapeutic efficacy of Methyldopa can be decreased when used in combination with Acepromazine.
Acetaminophen
Acetaminophen may decrease the excretion rate of Methyldopa which could result in a higher serum level.
Acetazolamide
Acetazolamide may increase the excretion rate of Methyldopa which could result in a lower serum level and potentially a reduction in efficacy.
Acetylsalicylic acid
The therapeutic efficacy of Methyldopa can be decreased when used in combination with Acetylsalicylic acid.
Acipimox
The risk or severity of myopathy, rhabdomyolysis, and myoglobinuria can be increased when Methyldopa is combined with Acipimox.
Aclidinium
Methyldopa may decrease the excretion rate of Aclidinium which could result in a higher serum level.
7 References
  1. 1 . Mah GT, Tejani AM, Musini VM: Methyldopa for primary hypertension. Cochrane Database Syst Rev. 2009 Oct 7;(4):CD003893. doi: 10.1002/14651858.CD003893.pub3.PubMed: 19821316
  2. 2 . McCoy S, Baldwin K: Pharmacotherapeutic options for the treatment of preeclampsia. Am J Health Syst Pharm. 2009 Feb 15;66(4):337-44. doi: 10.2146/ajhp080104.PubMed: 19202042
  3. 3 . Sica DA: Centrally acting antihypertensive agents: an update. J Clin Hypertens (Greenwich). 2007 May;9(5):399-405.PubMed: 17485976
  4. 4 . van Zwieten PA: Development and trends in the drug treatment of essential hypertension. J Hypertens Suppl. 1992 Dec;10(7):S1-12.PubMed: 1363322
  5. 5 . Rosenthal T, Oparil S: The effect of antihypertensive drugs on the fetus. J Hum Hypertens. 2002 May;16(5):293-8.PubMed: 12082488
  6. 6 . van Zwieten PA, Timmermans PB: Pharmacology and characterization of central alpha-adrenoceptors involved in the effect of centrally acting antihypertensive drugs. Chest. 1983 Feb;83(2 Suppl):340-3.PubMed: 6295709
  7. 7 . van Zwieten PA: Pharmacology of centrally acting hypotensive drugs. Br J Clin Pharmacol. 1980;10 Suppl 1:13S-20S.PubMed: 6104975