Deadly Drug Combo Involving COVID-19 Antiviral and Blood Pressure Med Found to Trigger Complete Heart Block!
Nikhil Prasad Fact checked by:Thailand Medical News Team Apr 22, 2025 3 hours, 19 minutes ago
Medical News: A Silent Danger Unveiled in a Rare Medical Case
In a shocking medical case that underscores the critical dangers of overlooked drug interactions, a team of doctors from the UMass Chan Medical School in Worcester, Massachusetts-USA, has documented how a commonly prescribed COVID-19 antiviral—nirmatrelvir-ritonavir (Paxlovid)—when taken alongside the blood pressure medication verapamil, triggered complete heart block and near-fatal shock in a 58-year-old woman.
Deadly Drug Combo Involving COVID-19 Antiviral and Blood Pressure Med Found to Trigger Complete Heart Block!
This
Medical News report highlights a potentially life-threatening scenario that might be quietly unfolding in patients with complex medical histories and multiple prescriptions. The woman, who had tested positive for COVID-19 a week prior, was prescribed Paxlovid, a drug known to interfere with other medications due to its strong inhibition of a liver enzyme called CYP3A4. The enzyme is crucial for breaking down many drugs, including verapamil. Within days of starting Paxlovid, the woman experienced alarming symptoms—shortness of breath, nausea, and leg swelling—and arrived at the hospital in a state of severe bradycardia, with a heart rate of only 34 beats per minute and blood pressure of 75/39 mm Hg.
An Overlooked and Dangerous Interaction
The patient had a complex history including type 2 diabetes, obesity, high blood pressure, chronic kidney disease, and cirrhosis from liver dysfunction. Her long-term use of verapamil, combined with the CYP3A4-inhibiting effects of ritonavir in Paxlovid, likely led to a dangerous buildup of verapamil in her system. The acute kidney injury she experienced further worsened the situation by impairing drug clearance.
Electrocardiograms (ECGs) showed intermittent complete heart block with right bundle branch block. The team rapidly diagnosed verapamil toxicity and initiated emergency treatment, including IV fluids, norepinephrine for blood pressure support, and calcium gluconate to counteract the effects of the calcium-channel blocker.
A Fast Turnaround with the Right Interventions
Remarkably, within 30 minutes of calcium therapy, the woman’s heart rhythm began to stabilize. By the next morning, her ECG returned to a normal sinus rhythm, and her blood pressure normalized. She was discharged just days later with no lingering heart rhythm issues, though verapamil was permanently discontinued.
Three months after the incident, she began taking diltiazem—a similar drug but with a different interaction profile—and has remained symptom-free since. However, the trauma has left her deeply concerned about future drug interactions, especially considering her need to manage multiple chronic conditions.
The Underreported Threat in COVID Drug Use
According to the researchers—Drs. Evan Offord, Michelle Nabi, Michael Mankbadi, Alexandra Marchetta, and Lawrence Rosenthal&
;mdash;this is only the third reported case of such a dangerous interaction between nirmatrelvir-ritonavir and verapamil. In one previous instance, the outcome was fatal.
The key danger lies in the fact that the antiviral and verapamil are often prescribed for completely different conditions, leading to a false sense of safety in co-administration. Paxlovid’s own fact sheet lists potential interactions with calcium channel blockers, but these warnings may be overlooked in high-pressure clinical settings, especially when treating COVID-19 patients urgently.
The team used the Naranjo Scale, a standard tool to evaluate the likelihood of adverse drug reactions, and scored the interaction as "probable" based on consistent timing, clinical symptoms, and the patient's improvement after discontinuation and treatment.
Why Verapamil Became Toxic
Verapamil is broken down mainly by the liver enzyme CYP3A4, and it is also excreted in small amounts by the kidneys. Ritonavir, a powerful CYP3A4 inhibitor in Paxlovid, disrupts verapamil’s metabolism, causing its levels to rise dangerously in the body. The patient's liver cirrhosis and kidney injury further hampered this process, creating a perfect storm for cardiac toxicity.
With no standardized treatment protocol for verapamil toxicity, the medical team used a combination of calcium therapy and blood pressure support. In extreme cases, treatments might include insulin drips, lipid infusions to bind the drug, pacemakers, or even mechanical heart and lung support systems.
Conclusions
This case serves as a critical warning to physicians prescribing COVID-19 treatments for patients already taking medications like verapamil. The interaction between Paxlovid and verapamil can be deadly, especially in patients with impaired liver or kidney function. Healthcare providers must be vigilant in reviewing all medications before initiating treatment and consider alternative therapies when risks are evident. Patients should also be educated about potential interactions, especially when managing multiple chronic illnesses. Preventing these avoidable tragedies starts with awareness and careful prescribing practices.
The study findings were published in the peer reviewed journal: JACC Case Reports.
https://www.sciencedirect.com/science/article/pii/S2666084925000087
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