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Side Effects of Lansoprazole (Prevacid)


Side Effects of Lansoprazole (Prevacid)

Lansoprazole, available as the brand Prevacid is a prescription medication belonging to the group of proton pump inhibitors (PPIs). Prevacid reduces the amount of acid in your stomach.

Before Prevacid Treatment

The FDA provides warnings before beginning Prevacid treatment. Some people may experience severe diarrhea, due to Clostridium difficile infection in intestines that can present itself as watery stools, stomach pain and fever. Fractures of the hip, wrist, or spine is another serious side effect of Prevacid which is more commonly seen in people who take multiple daily doses of PPI for more than one year. For this reason, Prevacid should be taken exactly as prescribed.


Prevacid reduces the amount of acid in your stomach that is needed to absorb Vitamin B12 adequately in the body. This can lead to vitamin B12 deficiency, especially, if you take it for more than three years. If you take proton pump inhibitor medications for at least 3 months magnesium levels may change. If low magnesium levels happen, it is usually after a year of treatment.

Serious Side Effects

According to the Prevacid label reported by the FDA, this medication increases the risk of severe diarrhea and bone fractures in the hip, wrists or spine.

Common Side Effects

Common Prevacid reactions are:


  • Diarrhea
  • Stomach pain
  • Nausea
  • Constipation
  • Headache


(Prevacid label reported by the FDA).

Less Common Side Effects

Less common side effects of Prevacid include fever, flu syndrome, halitosis (bad breath), infection, malaise (discomofort), neck pain and rigidity, pelvic pain, arrhythmia (irregular heartbeat), bradycardia (slow heart rate), hypertension (unusually high blood pressure), abnormal stools, anorexia, bezoar (undigested material stuck in the stomach), cardiospasm (difficulty in food and liquid passing to the stomach), cholelithiasis (gallstones presented in the gallbladder), colitis (colon inflammation), dry mouth, and dyspepsia (indigestion).


Other rare side effects are:


  • Dysphagia (difficulty in swallowing)
  • Enteritis (inflammation of the intestine)
  • Eructation (belching)
  • Esophageal stenosis (the esophagus becomes narrow)
  • Esophageal ulcer
  • Esophagitis (inflammation of the esophagus)
  • Discoloration of the feces
  • Flatulence (gas)
  • Gastric nodules/fundic gland polyps (can be cancerous)

About Pharmacogenetic Testing

Prevacid is predominantly metabolized in the body by CYP2C19 and CYP3A4 according to the Prevacid label reported by the FDA . Of these, CYP2C19 enzyme activity varies considerably due to genetic differences. Due to this, individuals with increased CYP2C19 activity, known as ultra rapid metabolizers may have an inadequate response that makes Prevacid ineffective in standard doses, according to PharmGKB. Those with low to minimal activity of CYP2C19, termed “poor metabolizers” are likely to experience high blood levels, potentially making them more susceptible to serious side effects.

Know Your Risk with the Rxight® Genetic Test

Rxight® genetic testing is a valuable clinical tool in selecting patients to ensure optimal Prevacid therapy. Rxight® tests your genetically encoded metabolism of hundreds of clinically relevant medications to determine how you will react to them, preferably before you even begin treatment. That way, you and your prescriber can determine the dose that is tailored to your unique genetics.


To learn more about Rxight®, contact us at 1-888-888-1932 or at support@Rxight.com.


Contributors to this Article:
Michael Sapko, MD, PhD; and Deborah Kallick, PhD, Medicinal Chemistry

Read more about Rxight® : What is Pharmacogenetics?