Does terbinafine interact with lisinopril (Angiotensin-Converting Enzyme (ACE) inhibitor) or hydrochlorothiazide (HCTZ) (thiazide diuretic)?

Terbinafine Does Not Have Clinically Significant Interactions with Lisinopril or Hydrochlorothiazide

Terbinafine does not have clinically significant interactions with lisinopril or hydrochlorothiazide, making it a safe combination therapy with no concerns regarding mortality, morbidity, or quality of life. 1

Pharmacological Properties and Interaction Profile

Terbinafine is an allylamine antifungal agent commonly prescribed for the treatment of dermatomycoses and onychomycoses. It works by inhibiting squalene epoxidase, which disrupts ergosterol synthesis in fungal cell membranes, resulting in both fungistatic and fungicidal effects 2.

The interaction profile of terbinafine is characterized by:

• Primarily interacting with drugs metabolized by cytochrome P450 2D6 (CYP2D6) isoenzyme 1
• Having minimal drug-drug interactions overall, making it generally safe for use in older and multimorbid patients 3
• Low potential for drug interactions compared to azole antifungals 4, 2

Terbinafine with Antihypertensive Medications

Interaction with Lisinopril

• Lisinopril is an ACE inhibitor that is not metabolized by the CYP450 enzyme system
• Lisinopril is primarily eliminated unchanged by the kidneys 5
• No documented interactions between terbinafine and lisinopril exist in the clinical literature
• Terbinafine's selective inhibition of CYP2D6 does not affect lisinopril's pharmacokinetics

Interaction with Hydrochlorothiazide

• Hydrochlorothiazide is a thiazide diuretic that is not metabolized by the CYP450 enzyme system
• Hydrochlorothiazide is primarily eliminated unchanged by the kidneys 5
• No documented interactions between terbinafine and hydrochlorothiazide exist in the clinical literature
• A study examining the pharmacokinetics of lisinopril and hydrochlorothiazide found no clinically relevant pharmacokinetic interactions between these two components 6, further supporting the safety of adding terbinafine to this combination

Clinical Implications

When prescribing terbinafine to patients taking lisinopril or hydrochlorothiazide:

• No dosage adjustments are necessary for any of these medications
• Regular monitoring of blood pressure should continue as usual
• Standard monitoring for potential side effects of each individual medication should be maintained

Known Drug Interactions with Terbinafine

While terbinafine does not interact with lisinopril or hydrochlorothiazide, clinicians should be aware of other potential interactions:

• Terbinafine may interact with certain antidepressants (particularly tricyclics) and some cardiovascular drugs metabolized by CYP2D6 3
• Caution is advised when combining terbinafine with tamoxifen, as terbinafine can reduce tamoxifen's efficacy by inhibiting the formation of its active metabolite, endoxifen 3
• Drug interactions with terbinafine can be prolonged due to its long elimination half-life (reported range 17-400 hours), with interactions potentially persisting for up to 3-6 months after discontinuation 7

Conclusion

Terbinafine can be safely administered to patients taking lisinopril or hydrochlorothiazide without concerns about clinically significant drug interactions affecting morbidity, mortality, or quality of life. This makes terbinafine an appropriate antifungal choice for hypertensive patients on these medications.