Drug General Information (ID: DDIU7S2NH9)
  Drug Name Methyldopa Drug Info Penbutolol Drug Info
  Drug Type Small molecule Small molecule
  Therapeutic Class Antihypertensive Agents Antihypertensive Agents
  Structure

 Mechanism of Methyldopa-Penbutolol Interaction (Severity Level: Moderate)
     Additive hypotensive effects Click to Show/Hide Mechanism Graph
Could Not Find 2D Structure
      Drug Name Methyldopa Penbutolol
      Mechanism Antihypertensive agent
Alpha-2 adrenergic receptor  Agonist
Antihypertensive agent
Beta-1 adrenergic receptor  Antagonist
      Key Mechanism Factor 1
Factor Name Adrenergic receptor alpha-2 Structure Sequence
Protein Family G-protein coupled receptor 1 family
Protein Function
Alpha-2 adrenergic receptors mediate the catecholamine-induced inhibition of adenylate cyclase through the action of G proteins. The rank order of potency for agonists of this receptor is oxymetazoline > clonidine > epinephrine > norepinephrine > phenylephrine > dopamine > p-synephrine > p-tyramine > serotonin = p-octopamine. For antagonists, the rank order is yohimbine > phentolamine = mianserine > chlorpromazine = spiperone = prazosin > propanolol > alprenolol = pindolol.
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      Key Mechanism Factor 2
Factor Name Adrenergic receptor beta-1
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Structure Sequence
MGAGVLVLGASEPGNLSSAAPLPDGAATAARLLVPASPPASLLPPASESPEPLSQQWTAGMGLLMALIVLLIVAGNVLVIVAIAKTPRLQTLTNLFIMSLASADLVMGLLVVPFGATIVVWGRWEYGSFFCELWTSVDVLCVTASIETLCVIALDRYLAITSPFRYQSLLTRARARGLVCTVWAISALVSFLPILMHWWRAESDEARRCYNDPKCCDFVTNRAYAIASSVVSFYVPLCIMAFVYLRVFREAQKQVKKIDSCERRFLGGPARPPSPSPSPVPAPAPPPGPPRPAAAAATAPLANGRAGKRRPSRLVALREQKALKTLGIIMGVFTLCWLPFFLANVVKAFHRELVPDRLFVFFNWLGYANSAFNPIIYCRSPDFRKAFQRLLCCARRAARRRHATHGDRPRASGCLARPGPPPSPGAASDDDDDDVVGATPPARLLEPWAGCNGGAAADSDSSLDEPCRPGFASESKV
Gene Name ADRB1
Uniprot ID ADRB1_HUMAN
KEGG Pathway hsa:153
Protein Family G-protein coupled receptor 1 family
Protein Function
Beta-adrenergic receptors mediate the catecholamine-induced activation of adenylate cyclase through the action of G proteins. This receptor binds epinephrine and norepinephrine with approximately equal affinity. Mediates Ras activation through G(s)-alpha- and cAMP-mediated signaling. Involved in the regulation of sleep/wake behaviors (PubMed:31473062).
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      Mechanism Description
  • Additive hypotensive effects by the combination of Methyldopa and Penbutolol 

Recommended Action
      Management Close monitoring of blood pressure is recommended during concomitant use, and if methyldopa or the beta blocker are withdrawn from therapy. Methyldopa manufacturers recommend adjusting the beta blocker dose if methyldopa is added to therapy, and not exceeding a methyldopa dose of 500 mg/day when it is first added to therapy. Patients should be instructed to notify their doctor if they have a reduced heart rate, dizziness, fainting or headaches, chest pain or vision problems.

References
1 Cerner Multum, Inc. "Australian Product Information.".
2 Reidenberg MM "Drug Discontinuation Effects are Part of the Pharmacology of a Drug." J Pharmacol Exp Ther (2011):
3 Frishman WH "Beta-adrenergic receptor blockers. Adverse effects and drug interactions." Hypertension 11 (1988): II21-9