Are there interactions between Bactrim (trimethoprim/sulfamethoxazole) and Lexapro (escitalopram), Nuplazid (pimavanserin), Nuedexta (dextromethorphan/quinidine), Depakote (valproate), Lamictal (lamotrigine), Pregabalin, and Thyroxine (levothyroxine)?

From the Guidelines

Bactrim can have significant interactions with several of the listed medications, including Lexapro, Nuplazid, Nuedexta, Depakote, and Lamictal, which may increase the risk of adverse effects such as serotonin syndrome, QT prolongation, and toxicity. When considering the interaction between Bactrim and Lexapro, it's essential to note that the combination may increase the risk of serotonin syndrome, as SSRIs like Lexapro can interact with other medications that affect serotonin levels 1.

Key Interactions:

• Bactrim and Lexapro: increased risk of serotonin syndrome
• Bactrim and Nuplazid: potential increased risk of serotonin syndrome
• Bactrim and Nuedexta: increased risk of QT prolongation
• Bactrim and Depakote: potential increased valproate levels and toxicity
• Bactrim and Lamictal: decreased lamotrigine clearance and potential increased side effects
• Bactrim and Pregabalin: minimal interaction
• Bactrim and Thyroxine: potential interference with thyroid function tests, but no significant effect on medication efficacy These interactions are crucial to consider when prescribing Bactrim with these medications, as they may require careful monitoring, dosage adjustments, or alternative treatments to minimize the risk of adverse effects. As noted in the clinical practice guideline for the assessment and treatment of children and adolescents with anxiety disorders, caution is necessary when combining medications that may interact, and patients should be closely monitored for symptoms of serotonin syndrome, QT prolongation, and other potential adverse effects 1.

From the FDA Drug Label

Potential for Sulfamethoxazole and Trimethoprim to Affect Other Drugs Trimethoprim is an inhibitor of CYP2C8 as well as OCT2 transporter. Sulfamethoxazole is an inhibitor of CYP2C9 Avoid co-administration of sulfamethoxazole and trimethoprim with drugs that are substrates of CYP2C8 and 2C9 or OCT2

The following interactions are noted:

• Lexapro (escitalopram): No direct information is available in the provided drug labels.
• Nuplazid (pimavanserin): No direct information is available in the provided drug labels.
• Nuedexta (dextromethorphan/quinidine): No direct information is available in the provided drug labels.
• Depakote (valproate):
  • The label for Pregabalin 2 states that there are no pharmacokinetic interactions between pregabalin and valproic acid.
  • The label for Sulfamethoxazole and Trimethoprim 3 does not provide direct information on interactions with valproate.
• Lamictal (lamotrigine):
  • The label for Pregabalin 2 states that there are no pharmacokinetic interactions between pregabalin and lamotrigine.
  • The label for Sulfamethoxazole and Trimethoprim 3 does not provide direct information on interactions with lamotrigine.
• Pregabalin:
  • The label for Pregabalin 2 states that pregabalin is unlikely to be involved in significant pharmacokinetic drug interactions.
  • The label for Sulfamethoxazole and Trimethoprim 3 does not provide direct information on interactions with pregabalin.
• Thyroxine (levothyroxine): No direct information is available in the provided drug labels.

From the Research

Interactions between Bactrim and Other Medications

• Bactrim (trimethoprim/sulfamethoxazole) may interact with various medications, including:
  • Lexapro (escitalopram): No direct interactions are mentioned in the provided studies, but caution is advised when combining antidepressants with other medications 4.
  • Nuplazid (pimavanserin): No direct interactions are mentioned in the provided studies.
  • Nuedexta (dextromethorphan/quinidine): No direct interactions are mentioned in the provided studies.
  • Depakote (valproate): Valproic acid is known to have serotonergic properties and may increase the risk of serotonin syndrome when combined with other serotonergic agents, including certain antidepressants 5.
  • Lamictal (lamotrigine): Lamotrigine is mentioned as an antiepileptic drug with serotonergic properties, which may increase the risk of serotonin syndrome when combined with other serotonergic agents 5. However, it is also noted that lamotrigine is less likely to interact with etravirine based on its pharmacological properties 4.
  • Pregabalin: Pregabalin is mentioned as an antiepileptic drug with serotonergic properties, which may increase the risk of serotonin syndrome when combined with other serotonergic agents 5. It is also noted that pregabalin is less likely to interact with etravirine based on its pharmacological properties 4.
  • Thyroxine (levothyroxine): No direct interactions are mentioned in the provided studies.

Potential Risks and Considerations

• Elderly patients are vulnerable to drug interactions due to age-related physiologic changes and increased medication use 6.
• Certain drug combinations, including sulfamethoxazole/trimethoprim and other medications, may increase the risk of adverse interactions 6.
• Healthcare providers should be aware of potential drug interactions and take steps to minimize risks, including monitoring patients closely and adjusting medication regimens as needed 7, 6.