Date of report 04 Jul 2024
Reported case interaction between
 Lopinavir/Ritonavir and Terfenadine

FLS Science

Drugs suspected to be involved in the DDI

Perpetrator
Lopinavir/Ritonavir
Daily Dose
800 (mg)
Dose adjustment performed
No
Administration Route
Oral
Start date
Unknown
End date
Unknown
Victim
Terfenadine
Daily Dose
180 (mg)
Dose adjustment performed
No
Administration Route
Oral
Start date
Unknown
End date
Unknown

Complete list of drugs taken by the patient

Antiretroviral treatment
Lamivudine
Tenofovir-DF
Lopinavir/ritonavir
Complete list of all comedications taken by the patient, included that involved in the DDI

Terfenadine 60 mg 3x/day, prednisone 30 mg/day, 

Clinical case description

Gender
Female
Age
38
eGFR (mL/min)
>60
Liver function impairment
No
Description

A 38-year-old female on long-term antiretroviral treatment with lopinavir/r + lamivudine + TDF presented a loss of consciousness and convulsion during her sleep. She was admitted to the emergency department. The heart monitoring showed ventricular fibrillation which was resolved with defibrillation, restoring her consciousness. She reported being prescribed terfenadine and prednisone for urticaria. After 3 days on this medication, she suddenly lost her consciousness and presented alterations  of the electrocardiogram characterized by QT prolongation and torsade pointes which occurred several times for a period of 2 days. This clinical presentation was attributed to the interaction between lopinavir/ritonavir and terfenadine. Ritonavir strongly inhibits CYP3A4 which is the main enzyme metabolizing terfenadine.

This case was published by Mu X et al. Front Pharmacol 2023.

Clinical Outcome

Toxicity

Drug Interaction Probability Scale (DIPS)

Score
7 - Probable

Editorial Comment

Coadministration of lopinavir and terfenadine is contraindicated due to the potential for serious and/or life-threatening reactions such as cardiac arrhythmias.
This clinical case is of special interest because the interaction it presents poses a risk of alterations in cardiac electrophysiology, such as prolonging the QT interval. Such interactions can go unnoticed or be underestimated, despite their potential seriousness, which can compromise the patient's life, as illustrated in this case. Therefore, it is important to emphasize the need for special care with this type of interaction.

University of Liverpool Recommendation

These drugs should not be coadministered
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