In this drug factsheet:
What side effects are possible with this medication?
Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent. The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.
The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.
Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.
- abdominal or stomach pain
- diarrhea or loose stools
- dry mouth
- general feeling of being unwell
Although most of these side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.
Check with your doctor as soon as possible if any of the following side effects occur:
- changes in vision
- diarrhea (watery and severe; may also be bloody)
- increased sensitivity to sunlight
- joint pain
- mild skin rash or itching
- muscle aches or cramps
- pain or burning in the mouth or throat
- signs of electrolyte imbalance (e.g., muscle pain or cramps, weakness, irregular heart beat)
- signs of liver damage (yellow skin or eyes, dark urine, loss of appetite, abdominal pain, fever, and fatigue)
- swelling of the hands or feet (if there is no shortness of breath)
Stop taking the medication and seek immediate medical attention if any of the following occur:
- signs of an allergic reaction (e.g., difficulty breathing, hives, swelling of the face or throat)
- signs of bleeding in the stomach (e.g., bloody, black, or tarry stools, spitting up of blood, vomiting blood or material that looks like coffee grounds)
- signs of a severe skin reaction such as blistering, peeling, a rash covering a large area of the body, a rash that spreads quickly, or a rash combined with fever or discomfort
Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.
Are there any other precautions or warnings for this medication?
Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.
Diarrhea: When gastric acid is decreased, the number of bacteria normally in the digestive system increases. Occasionally, this can cause serious infection in the digestive tract. If you experience watery, foul-smelling bowel movements after starting to take omeprazole, contact your doctor as soon as possible.
Fluid and electrolyte balance: Omeprazole, like other PPIs, may cause the levels of electrolytes such as potassium, sodium, magnesium, chloride, and calcium in the blood to change while taking this medication. If you experience symptoms of fluid and electrolyte imbalance such as muscle pains or cramps; dry mouth; numb hands, feet, or lips; or racing heartbeat, contact your doctor as soon as possible. Your doctor will do blood tests regularly to monitor the levels of these electrolytes in your blood while you are taking this medication.
Liver disease: People with severe liver disease should generally not take more than 20 mg of omeprazole daily.
Methotrexate interaction: Omeprazole, like other medications in this group, may interact with methotrexate when the two medications are used at the same time. This combination may lead to higher than expected amounts of methotrexate in the body and can cause serious side effects, including kidney damage, irregular heartbeat, anemia, or infection. If you take omeprazole and are also going to receive a dose of methotrexate, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.
Osteoporosis-related fractures: Studies suggest that the use of omeprazole, like other PPIs may be related to an increase risk of fractures, particularly for people who take this medication for a year or longer. The lowest dose of this medication to control the symptoms, taken for the shortest period of time is less likely to cause these problems.
Severe stomach problems: If you have recurrent vomiting, difficulty swallowing, blood in the stool, coughing up of blood, or significant unintentional weight loss, check with your doctor immediately.
Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, call your doctor immediately.
Breast-feeding: It is not known if omeprazole passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.
Children: The safety and effectiveness of using this medication have not been established for children.
Seniors: Using the same dosage, seniors reach higher blood levels of omeprazole than younger people. Therefore, seniors may need to take reduced doses and should generally not take more than 20 mg of omeprazole daily.
What other drugs could interact with this medication?
There may be an interaction between omeprazole and any of the following:
- amphetamines (e.g., dextroamphetamine, lisdexamphetamine)
- "azole" antifungals (e.g., itraconazole, ketoconazole, voriconazole)
- benzodiazepines (e.g., alprazolam, diazepam, lorazepam)
- bisphosphonates (e.g., alendronate, etidronate)
- HIV protease inhibitors (e.g., atazanavir, indinavir, ritonavir, saquinavir)
- iron salts (e.g., ferrous fumarate, ferrous sulphate)
- multivitamins with iron, folate
- other proton pump inhibitors (e.g., esomeprazole, lansoprazole)
- peginterferon Alfa-2b
- "statin" anti-cholesterol medications (e.g., atorvastatin, lovastatin, simvastatin)
- St. John's wort
- tricyclic antidepressasnts (e.g., amitriptyline, clomipramine, desipramine, trimipramine)
If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:
- stop taking one of the medications,
- change one of the medications to another,
- change how you are taking one or both of the medications, or
- leave everything as is.
An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.
Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.