Drug General Information (ID: DDIANDMQTL)
  Drug Name Valproic acid Drug Info Lamotrigine Drug Info
  Drug Type Small molecule Small molecule
  Therapeutic Class Anticonvulsants Anticonvulsants
  Structure

 Mechanism of Valproic acid-Lamotrigine Interaction (Severity Level: Major)
     UGT inhibition Click to Show/Hide Mechanism Graph
Could Not Find 2D Structure
      Drug Name Valproic acid Lamotrigine
      Mechanism UGT1A1 inhibitor UGT1A1 substrate
      Key Mechanism Factor 1
Factor Name UDP-glucuronosyltransferase 1A1
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Structure Sequence
MAVESQGGRPLVLGLLLCVLGPVVSHAGKILLIPVDGSHWLSMLGAIQQLQQRGHEIVVLAPDASLYIRDGAFYTLKTYPVPFQREDVKESFVSLGHNVFENDSFLQRVIKTYKKIKKDSAMLLSGCSHLLHNKELMASLAESSFDVMLTDPFLPCSPIVAQYLSLPTVFFLHALPCSLEFEATQCPNPFSYVPRPLSSHSDHMTFLQRVKNMLIAFSQNFLCDVVYSPYATLASEFLQREVTVQDLLSSASVWLFRSDFVKDYPRPIMPNMVFVGGINCLHQNPLSQEFEAYINASGEHGIVVFSLGSMVSEIPEKKAMAIADALGKIPQTVLWRYTGTRPSNLANNTILVKWLPQNDLLGHPMTRAFITHAGSHGVYESICNGVPMVMMPLFGDQMDNAKRMETKGAGVTLNVLEMTSEDLENALKAVINDKSYKENIMRLSSLHKDRPVEPLDLAVFWVEFVMRHKGAPHLRPAAHDLTWYQYHSLDVIGFLLAVVLTVAFITFKCCAYGYRKCLGKKGRVKKAHKSKTH
Gene Name UGT1A1
Uniprot ID UD11_HUMAN
KEGG Pathway hsa:54658
Protein Family UDP-glycosyltransferase family
Protein Function
[Isoform 1]: UDP-glucuronosyltransferase (UGT) that catalyzes phase II biotransformation reactions in which lipophilic substrates are conjugated with glucuronic acid to increase the metabolite's water solubility, thereby facilitating excretion into either the urine or bile (PubMed:12181437, PubMed:15472229, PubMed:18004206, PubMed:18004212, PubMed:18719240, PubMed:19830808, PubMed:23288867). Essential for the elimination and detoxification of drugs, xenobiotics and endogenous compounds (PubMed:12181437, PubMed:18004206, PubMed:18004212). Catalyzes the glucuronidation of endogenous estrogen hormones such as estradiol, estrone and estriol (PubMed:15472229, PubMed:18719240, PubMed:23288867). Involved in the glucuronidation of bilirubin, a degradation product occurring in the normal catabolic pathway that breaks down heme in vertebrates (PubMed:17187418, PubMed:18004206, PubMed:19830808). Also catalyzes the glucuronidation the isoflavones genistein, daidzein, glycitein, formononetin, biochanin A and prunetin, which are phytoestrogens with anticancer and cardiovascular properties (PubMed:18052087, PubMed:19545173). Involved in the glucuronidation of the AGTR1 angiotensin receptor antagonist losartan, a drug which can inhibit the effect of angiotensin II (PubMed:18674515). Involved in the biotransformation of 7-ethyl-10-hydroxycamptothecin (SN-38), the pharmacologically active metabolite of the anticancer drug irinotecan (PubMed:12181437, PubMed:18004212, PubMed:20610558).
    Click to Show/Hide
      Mechanism Description
  • Decreased metabolism of Lamotrigine caused by Valproic acid mediated inhibition of UGT

Recommended Action
      Management When coadministered with valproic acid, the dosage of lamotrigine should be half that required in the absence of valproic acid. Patients should be advised to promptly notify their physician if they experience early manifestations of hypersensitivity such as fever, angioedema, and lymphadenopathy, even if a rash is not evident. Lamotrigine should be discontinued if an alternative etiology for these symptoms cannot be established. Likewise, the drug should be discontinued at the first sign of rash, unless the rash is clearly not drug-related.

References
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2 Battino D, Croci D, Granata T, Mamoli D, Messina S, Perucca E "Single-dose pharmacokinetics of lamotrigine in children: Influence of age and antiepileptic comedication." Ther Drug Monit 23 (2001): 217-22. [PMID: 11360028]
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9 Magdalou J, Herber R, Bidault R, Siest G "In vitro N-glucuronidation of a novel antiepileptic drug, lamotrigine, by human liver microsomes." J Pharmacol Exp Ther 260 (1992): 1166-73. [PMID: 1545383]
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16 Product Information. Lamictal (lamotrigine). Glaxo Wellcome, Research Triangle Park, NC.
17 Reutens DC, Duncan JS, Patsalos PN "Disabling tremor after lamotrigine with sodium valproate." Lancet 342 (1993): 185-6. [PMID: 8101290]
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21 Vauzelle-Kervroedan F, Rey E, Cieuta C, et al. "Influence of concurrent antiepileptic medication on the pharmacokinetics of lamotrigine as add-on therapy in epileptic children." Br J Clin Pharmacol 41 (1996): 325-30. [PMID: 8730979]
22 Wadelius M, Karlsson T, Wadelius C, Rane A "Lamotrigine and toxic epidermal necrolysis." Lancet 348 (1996): 1041. [PMID: 8855897]
23 Wong IC, Mawer GE, Sander JW "Factors influencing the incidence of lamotrigine-related skin rash." Ann Pharmacother 33 (1999): 1037-42. [PMID: 10534214]
24 Yuen AW, Land G, Weatherley BC, Peck AW "Sodium valproate acutely inhibits lamotrigine metabolism." Br J Clin Pharmacol 33 (1992): 511-3. [PMID: 1524964]