Can You Switch Between Losartan And Lisinopril?

Traveler asked

I am currently on a daily dose of Losartan, which is working very well. I will run out of pills about 10 days before I can reach a pharmacy. I still have pills from my Lisinopril prescription, which was replaced by my doctor due to the dry cough side effect. My question is, can I take the Lisinopril as a replacement for the 10 days?

Answer

You shouldn't switch between losartan and lisinopril without first talking to your doctor.

However, due to their similar mechanism of action (they work on the same pathway), switching between them will most likely be safe if you have no other options. Be sure to contact your doctor just to be sure you don't have any contraindications with lisinopril.

Difference Between Lisinopril And Losartan

Lisinopril is an 'ACE-Inhibitor' (Angiotensin Converting Enzyme Inhibitor) while Losartan is classified as an 'ARB' (Angiotensin II Receptor Blocker). As mentioned above, they work on the same pathway to decrease blood pressure:

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Lisinopril (Zestril) blocks the conversion of angiotensin I to angiotensin II. Angiotensin II is a potent vasoconstrictor and has a variety of other effects, including:

• Reabsorption of sodium (increasing sodium levels)
• Retention of water
• Stimulation of the synthesis and secretion of aldosterone
• Activation of the sympathetic system (increasing heart rate)

Losartan (Cozaar) works further down in the pathway and blocks angiotensin II from binding to angiotensin I receptors. This blocks the effects listed above (e.g. vasoconstriction, water, and sodium retention, etc...).

Lisinopril and losartan share a similar side effect profile but losartan (and all ARBs) is not associated with the dry, unproductive cough that can be caused by ACE-inhibitors. This is because it doesn't affect the levels of bradykinin, which is thought to be responsible for the cough effects of ACE-Inhibitors.

Switching Between Losartan And Lisinopril

As discussed above, losartan and lisinopril work on the same pathway, but at different points.

They do have similar blood pressure lowering effects but studies indicate that ACE-Inhibitors may be more effective for certain indications, like chronic heart failure. In addition, they don't have equivalent dosages and there is no set in stone conversion guidelines.

Lisinopril is available in the following strengths:

• 2.5 mg
• 5 mg
• 10 mg
• 20 mg
• 40 mg

Losartan is available in the following strengths:

• 25 mg
• 50 mg
• 100 mg

Typically, when switching from one to the other, the old agent is discontinued and the new one is initiated at the lowest possible dose and titrated up.

Be sure to speak with your doctor regarding whether or not they recommend you to switch to lisinopril temporarily. There are many factors to consider (e.g. the dose you were taking, kidney function, other contraindications) and they have your complete medical history.