Prilosec - Interactions | Adverse effects

This article was medically reviewed by M.Pharm, Marko Tanaskovic on August 12, 2018. To read more about an author, click here.

Prilosec as an active substance contains omeprazole and belongs to the group of proton pump inhibitors. Prilosec blocks basal and stimulated secretion of hydrochloric acid in the stomach and relieves the symptoms of the following diseases:

  • Gastroesophageal reflux
  • Zollinger-Ellison syndrome
  • Gastric ulcer
  • Duodenal ulcer


Prilosec can lead to acute interstitial nephritis (inflammation of the spaces between the renal tubules where urine formation takes place). If you notice symptoms, such as:

  1. burning or pain during urination
  2. blood in the urine
  3. dark-colored urine or pelvic pain

you should immediately contact your doctor. Prilosec-induced interstitial nephritis occurs even at therapeutic dosages (20 mg and 40 mg). It can occur two weeks - six months after starting the drug. Fortunately, symptoms withdrawal and full recovery is achieved only a few days after cessation of drug. However, Prilosec should be avoided in patients who already have kidney problems.

Hepatotoxic adverse associated with this drug have been very rarely reported. There are only a few described cases so far and the most commonly signs of hepatotoxicity develop rapidly after drug administration (7-20 days after starting therapy). If you notice signs of hepatotoxicity (pain in the right upper abdomen and jaundice) you should stop taking this medication immediately. The symptoms of hepatotoxicity disappear quickly after treatment discontinuation. Prilosec-induced hepatitis has been reported in the pediatric population as well.1 It should be used with caution in patients who already have liver damage.

Rare cases of severe Prilosec-induced hyponatremia (low sodium level in the blood) have been reported. If you notice hyponatremia signs, such as:

  • nausea
  • vomiting
  • fatigue
  • impaired consciousness
  • headache and convulsions

you should immediately contact your doctor. This side effect occurs very quickly after drug administration, but it also disappears very quickly after discontinuation of therapy.

With regard to reducing the acid secretion, Prilosec can also reduce the utilization of vitamin B 12, and chronic administration of this medicine can lead to a vitamin B12 deficiency and consequently to anemia. It is desirable to run blood tests regularly (every 2-3 months) while on Prilosec.

The chronic use of this drug can negatively impact absorption of calcium and magnesium, which can lead to osteoporosis (reduction of bone density and consequently a higher risk for bone fractures). Patients who already have an increased risk of developing osteoporosis (e.g. postmenopausal women) should avoid chronic use of this drug.

Prilosec, pregnancy and breastfeeding

In multicentre, prospective clinical study conducted on 113 pregnant women who took Prilosec, an increased risk of spontaneous abortion or perinatal complications has not been established.2 Some studies conducted on animals have shown that this drug increases the risk of miscarriage. Manufacturer recommends that this drug should be used during pregnancy only if clearly needed.

Since it is excreted into breast milk and could affect the gastric secretion in infants, Prilosec should not be used during breastfeeding.

How to use

The recommended dose is 20 mg or 40 mg once a day, in the morning on an empty stomach. For severe forms the dose can be increased to 40 mg twice a day.


Prilosec can interact with the following medicines:

  • Citalopram (a drug used to treat depression). Prilosec increases the concentration of citalopram in the blood, thus leading to an increase in the serotonin levels in the blood and to the serotonin syndrome (a serious condition characterized by arrhythmias).
  • Cilostazol - used to relieve the symptoms of intermittent claudication. Concomitant use increases the risk of side effects (dizziness, palpitations and arrhythmia).
  • Atazanavir - used to treat AIDS. Prilosec reduces the absorption of this drug in the stomach, and may decrease its effectiveness in the treatment of AIDS.
  • Dasatinib - used for the treatment of leukemia (chronic myeloid and acute lymphoblastic leukemia). Concomitant use decreases dasatinib efficiency.
  • Nelfinavir and rilpivirine - medicines used to treat AIDS. Prilosec reduces the level of these drugs in the blood, which decreases their efficiency.
  • Erlotinib - used for the treatment of pancreatic cancer. Concomitant use reduces the level of erlotinib in the blood, which consequently decreases its effectiveness.
  • Methotrexate - used for the treatment of breast cancer. Prilosec increases the level of this drug in the blood which increases the risk of toxic effects.
  • Clopidogrel - antiplatelet drug used for the prevention of heart attack and stroke. Prilosec decreases effectiveness of this drug.

Adverse effects

Adverse effects of Prilosec include:

  • Nausea
  • Vomiting
  • Constipation
  • Headache
  • Dizziness
  • Osteoporosis
  • Vitamin B12 deficiency and anemia
  • Hyponatremia (impaired consciousness and convulsions)
  • Dry mouth
  • Hypocalcaemia
  • Hypophosphatemia
  • Oral infections caused by fungi
  • Arthralgia
  • Myalgia
  • Interstitial nephritis
  • Hallucinations
  • Aggressiveness
  • Gynecomastia in men
  • Alopecia


  1. NCBI link 1
  2. NCBI link 2

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