Can You Substitute Lisinopril For Losartan If You Run Out Of Meds?

Dorsey asked

I ran out of losartan. The pharmacy is closed on Sunday. Can I substitute liscinopril?

Answer

Hi Dorsey and thanks for reaching out to us. I understand that it’s tempting to try to substitute one drug for another if you run out, but it’s not a very safe thing to do.

First, a bit about both medications.

Lisinopril is in a class of medications called ACE-inhibitors. They work to lower the blood pressure by inhibiting an enzyme called angiotensin-converting enzyme. By doing this, they decrease a vasoconstrictor called angiotensin II from being made which helps to lower your blood pressure.

Losartan is what we call an “ARB” or an angiotensin receptor blocker. It works by binding to the angiotensin II receptor, so it blocks the vasoconstriction mentioned earlier.

While these medications work on the same pathway in your body to lower blood pressure, they are not the same. They both use very different strengths to achieve this as well so it’s not easy to convert between them. For example, while 10mg of lisinopril is a very common dose, 10mg of losartan would be an underdose in the vast majority of people.

Lastly, from a safety perspective, there’s a small chance that starting lisinopril (or any drug in the class) unsupervised could be dangerous. Between 0.1-0.7% of people starting an ACE inhibitor may experience angioedema. The face swells and sometimes the tongue or throat and requires immediate medical attention.

In this situation, I think it’s much safer to do without for the day and visit your pharmacy as soon as they open back up. As I also don't know your complete medical situation, you may want to double-check with your doctor for their advice as well.