Lansoprazole interacts with a surprisingly wide range of medications, supplements, and even herbal products. Some interactions are dangerous, others simply make one drug or the other less effective. The most important ones to know about involve certain HIV medications, blood thinners, heart drugs, antifungals, and a common herbal supplement.
HIV and Antiviral Medications
The most serious interaction involves rilpivirine, an HIV medication. Taking it with lansoprazole is contraindicated, meaning the combination should never be used. Another HIV drug, nelfinavir, should also be avoided entirely. The reason is straightforward: these medications need stomach acid to dissolve and absorb properly, and lansoprazole dramatically reduces acid production.
Research in healthy volunteers showed that lansoprazole reduced absorption of the HIV drug atazanavir by 94%. Peak blood levels dropped from 3.2 to just 0.13 micromoles. That’s not a small reduction; it’s near-total failure of the drug to enter the bloodstream. If you take any antiretroviral medication, your prescriber needs to know you’re on lansoprazole.
Blood Thinners and Antiplatelet Drugs
Lansoprazole can increase the blood-thinning effect of warfarin, raising the risk of abnormal or dangerous bleeding. If you take both, your clotting levels need to be monitored more frequently, especially when starting or stopping lansoprazole.
The interaction with clopidogrel (Plavix) is more nuanced. Clopidogrel needs to be converted into its active form by a liver enzyme called CYP2C19. Lansoprazole is the most potent inhibitor of that same enzyme among all proton pump inhibitors. Studies have linked “other PPIs” (including lansoprazole) with a 40% increase in the risk of recurrent heart attack in clopidogrel users, though the individual contribution of lansoprazole specifically isn’t fully separated out. If you’re on clopidogrel after a heart event, this combination deserves a conversation with your doctor.
Heart Medications: Digoxin
Lansoprazole can increase how much digoxin your body absorbs by changing stomach acid levels. Higher digoxin levels raise the risk of toxicity, which can cause nausea, vomiting, and abnormal heart rhythms. If you take both, your digoxin blood levels may need periodic checks.
Drugs That Need Stomach Acid to Work
Because lansoprazole raises stomach pH (makes it less acidic), any medication that relies on an acidic environment for absorption can be affected. This includes:
- Antifungal medications like ketoconazole and itraconazole
- Iron supplements
- Certain cancer drugs like erlotinib, dasatinib, and nilotinib
- Mycophenolate mofetil, an immune-suppressing drug used after organ transplants
These drugs may simply pass through your system without being properly absorbed. If you need both lansoprazole and one of these medications, your prescriber may adjust timing, switch drugs, or monitor levels more closely.
Methotrexate
Lansoprazole can slow the body’s ability to clear methotrexate, particularly at high doses used in cancer treatment. The proposed mechanism involves lansoprazole blocking certain pumps in the kidneys that normally flush methotrexate out of the body. When methotrexate lingers too long, it can cause kidney damage, dangerously low blood counts, severe mouth sores, and muscle injury.
That said, a prospective study of 28 rheumatoid arthritis patients taking low-dose methotrexate alongside lansoprazole for seven days found no change in methotrexate levels. The risk appears to be concentrated in patients on high-dose methotrexate for cancer, not the lower doses typically used for autoimmune conditions. Still, the FDA label recommends considering temporary withdrawal of lansoprazole during high-dose methotrexate treatment.
St. John’s Wort and Rifampin
St. John’s Wort, a popular herbal supplement for mood, and rifampin, an antibiotic used for tuberculosis, both rev up the liver enzymes that break down lansoprazole. The result is that lansoprazole gets cleared from your body too quickly to work properly. The FDA label advises avoiding both while on lansoprazole. This is an easy one to miss since many people don’t think of herbal supplements as “real” medications, but St. John’s Wort can effectively cancel out lansoprazole’s acid-suppressing effect.
On the flip side, certain medications slow down those same enzymes, causing lansoprazole to build up to higher-than-intended levels. The antifungal voriconazole and the antidepressant fluvoxamine are notable examples. Higher lansoprazole exposure increases the chance of side effects like headache, diarrhea, and, over time, the nutrient absorption issues described below.
Sucralfate Timing
Sucralfate, a medication that coats and protects stomach ulcers, physically interferes with lansoprazole absorption. If you take both, lansoprazole should be taken at least 30 minutes before sucralfate. Taking them together or in the wrong order means the lansoprazole may not work.
Tacrolimus
For organ transplant recipients taking tacrolimus, lansoprazole can raise tacrolimus blood levels, particularly in people whose bodies are naturally slower at processing certain drugs through the CYP2C19 enzyme pathway. This is relevant for a smaller group of people, but the consequences of tacrolimus levels climbing too high (kidney damage, tremors, high blood pressure) are serious enough that blood level monitoring is recommended.
Long-Term Effects on Vitamins and Minerals
Lansoprazole doesn’t “interact” with vitamins and minerals in the traditional sense, but long-term use can quietly reduce your body’s ability to absorb several key nutrients. Stomach acid plays a direct role in breaking down and absorbing iron, vitamin B12, and magnesium.
A 12-month study of patients on lansoprazole 30 mg daily found statistically significant drops in vitamin B12 levels, with lansoprazole showing the most pronounced B12 decline among the PPIs studied. However, actual clinical deficiency was uncommon: only about 3% of study participants developed low iron and roughly 3% developed low B12 over the year. The researchers concluded that routine screening isn’t necessary for most people, but monitoring is valuable for elderly or malnourished patients. Magnesium depletion is another recognized risk with long-term use, potentially causing muscle cramps, irregular heartbeat, and seizures in severe cases.
Food and Meal Timing
Lansoprazole itself is sensitive to food timing. Taking it 30 minutes after eating reduces absorption by 50% to 70% compared to taking it on an empty stomach. The FDA label is clear: take lansoprazole before meals. If you’ve been taking it with or after breakfast and feeling like it isn’t working well, timing could be the issue.
For people who have trouble swallowing the capsule, the granules can be sprinkled on applesauce, pudding, cottage cheese, yogurt, or strained pears and swallowed immediately. Other foods and liquids haven’t been tested for this purpose and aren’t recommended.
NSAIDs: A Special Case
Lansoprazole is frequently prescribed alongside NSAIDs like ibuprofen or naproxen specifically to protect the stomach lining from ulcers. This combination is intentional and generally beneficial for the stomach. However, research has shown that while PPIs protect the upper digestive tract, they may actually worsen NSAID-related injury to the small intestine by altering gut bacteria. For people at high risk of gastrointestinal bleeding who need to stay on NSAIDs, current guidelines recommend using lansoprazole with the lowest effective NSAID dose. But the PPI shouldn’t be dropped in chronic NSAID users who have bleeding risk.