Lansoprazole is a proton pump inhibitor that is used to treat and prevent stomach and intestinal ulcers, erosive esophagitis (damage to the esophagus from stomach acid), and other conditions involving excessive stomach acid such as Zollinger-Ellison syndrome.

Over-the-counter lansoprazole (Prevacid OTC) is used to treat frequent heartburn that happens 2 or more days per week.

Lansoprazole is not for immediate relief of heartburn symptoms.

Lansoprazole may also be used for purposes not listed in this medication guide.

Heartburn can mimic early symptoms of a heart attack. Get emergency medical help if you have chest pain that spreads to your jaw or shoulder and you feel anxious or light-headed.

You should not use this medicine if you are allergic to lansoprazole, or if you take any medicine that contains rilpivirine (Edurant, Complera, Odefsey).

Tell your doctor if you have ever had:

• liver disease;
• lupus;
• low levels of magnesium in your blood; or
• osteoporosis or low bone mineral density (osteopenia).

Do not use over-the-counter lansoprazole (Prevacid OTC) without the advice of a doctor if you have:

• trouble or pain with swallowing;
• bloody or black stools; vomit that looks like blood or coffee grounds;
• heartburn that has lasted for over 3 months;
• frequent chest pain, heartburn with wheezing;
• unexplained weight loss;
• nausea or vomiting, stomach pain; or
• an electrolyte imbalance or metabolic disorder.

Some forms of lansoprazole may contain phenylalanine. Tell your doctor if you have phenylketonuria (PKU).

You may be more likely to have a broken bone in your hip, wrist, or spine while taking a proton pump inhibitor long-term or more than once per day. Talk with your doctor about ways to keep your bones healthy.

Do not give lansoprazole to a child younger than 1 year old. Prevacid OTC is not approved for use by anyone younger than 18 years old.

Ask a doctor before using this medicine if you are pregnant or breastfeeding.

Use FIRST Lansoprazole (Oral) exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended.

Get emergency medical help if you have signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

• severe stomach pain, diarrhea that is watery or bloody;
• new or unusual pain in your wrist, back, hip, or thigh;
• a seizure (convulsions);
• kidney problems--fever, nausea, little or no urination, blood in your urine, swelling, rapid weight gain;
• low magnesium--dizziness, fast or irregular heart rate, tremors (shaking) or jerking muscle movements, feeling jittery, muscle cramps, muscle spasms in your hands and feet, cough or choking feeling; or
• new or worsening symptoms of lupus--joint pain, and a skin rash on your cheeks or arms that worsens in sunlight.

Taking lansoprazole long-term may cause you to develop stomach growths called fundic gland polyps. Talk with your doctor about this risk.

If you use lansoprazole for longer than 3 years, you could develop a vitamin B-12 deficiency. Talk to your doctor about how to manage this condition if you develop it.

Common side effects may include:

• nausea, stomach pain;
• diarrhea, constipation; or
• headache.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

This medicine can cause diarrhea, which may be a sign of a new infection. If you have diarrhea that is watery or bloody, call your doctor before using anti-diarrhea medicine.