Thiamine (Vitamin B1) Pharmacologic Interaction Risk With Lamotrigine and Adderall
Thiamine has no established clinically important pharmacologic interaction with lamotrigine or amphetamine/dextroamphetamine in major U.S. prescribing information. [1][2]
Pharmacokinetic Interaction Mechanisms for Lamotrigine
Lamotrigine is metabolized primarily by UGT-mediated glucuronidation. [1]
Drug interactions with lamotrigine in labeling are driven by drugs that induce or inhibit glucuronidation or related pathways. [1]
Thiamine is not identified as an established or potentially significant interacting drug in the lamotrigine drug-interaction tables. [1]
Pharmacokinetic Interaction Mechanisms for Amphetamine/Dextroamphetamine
Amphetamine/dextroamphetamine interactions in labeling focus on agents such as MAO inhibitors, serotonergic drugs, acidifying or alkalinizing agents, tricyclic antidepressants, CYP2D6 inhibitors, and other specified categories. [2]
Thiamine is not identified as a clinically important interacting agent in the amphetamine/dextroamphetamine interaction tables. [2]
Interaction Evidence Review Scope From Labeling
Lamotrigine labeling states that drugs other than those listed in the interaction tables have not been systematically evaluated with lamotrigine. [1]
Amphetamine/dextroamphetamine labeling similarly enumerates specific clinically important interacting drug categories and does not list thiamine. [2]
Practical Clinical Implications
Co-administration of thiamine with lamotrigine or Adderall does not require dose adjustment based on known labeled interaction pathways. [1][2]
Adverse effects or lack of therapeutic effect should be evaluated for other causes because thiamine is not a known interaction driver for these medications in labeling. [1][2]
When Additional Medication Review Is Indicated
Additional review is indicated when thiamine is taken as part of multi-ingredient supplements because other components may affect lamotrigine metabolism or amphetamine absorption/excretion depending on their pharmacology. [1][2]
Additional review is indicated when concurrent agents are present that are specifically listed as interactors with lamotrigine (e.g., UGT inducers or inhibitors) or with amphetamine/dextroamphetamine (e.g., MAO inhibitors, serotonergic drugs, acidifying/alkalinizing agents, CYP2D6 inhibitors). [1][2]