Last reviewed by Parth Dalal on September 4th, 2018.
What is “omeprazole”
Omeprazole is an antacid of class Proton Pump Inhibitors (PPI). Chemically it is 5-methoxy-2-[(4-methoxy-3,5-dimethylpyridin-2-yl)methylsulfinyl]-1H-benzimidazole and its molar mass is 345.42g/mol.
Omeprazole was marketed in United States by Astra AB now Astra Zeneca in 1989 under the brand name of Losec, due to confusion within brand name Laxis(furosemide) US FDA changed the brand name of omeprazole to Prilosec.
Antacids: An antacid is a substance which neutralizes the stomach acidity by controlling the acid production or neutralizing the excess acid produced in the stomach which in turn relieves heartburn, indigestion and upset stomach.
The recommended route of administration for omeprazole is oral. The dosage form developed for the drug are tablets, capsule and as powder for intravenous injection as omeprazole sodium. Different strengths are available of the drug omeprazole i.e. 10mg, 20mg & 40mg capsules and 20mg tablets. The recommended direction of use is one capsule or tablet before meals to be taken. The strength of omeprazole prescribed depends on the intensity of hyper acidity and age of the patients. It is used for neutralizing excess acid produced in the stomach which in turn relieves heartburn, indigestion and upset stomach.
How does omeprazole work
Mechanism of action: Omeprazole is a proton pump inhibitor and acts by suppressing the gastric acid secretion by specific inhibition of the H+/K+ – ATPase in the gastric parietal cell.
By acting specifically on the proton pump and blocking the exchange of ions omeprazole blocks the final step in acid production, thus reducing gastric acidity.
How long does it take for omeprazole to work
As once the drug is taken by oral means the effect is attained after hours and the maximum effect is attained within 2hours. At 24 hours inhibition, it is attained about 50% of maximum and the duration of inhibition lasts up to 72 hours.
Half-life of omeprazole is found to be very short, but last for long time due to prolonged binding to parietal h+/K+ – ATPase enzyme. Once daily dosing of omeprazole will enhance the action of inhibition of acid secretion, reaching plateau after four hours.
The body don’t let the drug to stay for long in the body, it absorbs the active ingredient and provides required pharmacological effect. The process is divided into four parts. They are:
Absorption: As the drug is acid labile it is prone to be affected in the stomach by the gastric juice such that the delayed release capsule and enteric coated tablets are required to avoid degradation by gastric juice.
One the omeprazole granules are available at the site of absorption the peak plasma levels are attained within 0.5 – 3.5 hours so it can be said that absorption is rapid.
The absolute bioavailability of the drug is about 30-40% with 20 – 40mg dose and absolute bioavailability slightly increases with repeated dosing. The bioavailability of the drug is found to be higher in elderly patients.
Distribution: It is highly plasma protein bounded about 95% and distribution of omeprazole is according to it.
Metabolism: Hepatic metabolism: The enzyme responsible for metabolism is cytochrome p450 enzyme system. Metabolism is stereo selective in nature and it is known that the drug omeprazole is a racemic mixture of S & R enantiomer.
The S isomer is converted into 5’O-desmethylomeprazole and the R isomer is converted into 5-hydroxyomeprazole and another enzyme of cytochrome P450 converts it into four different metabolites.
Elimination: The primary route of excretion of unchanged drug and its metabolites is urine and eliminates about 70% of the dose and the remaining is eliminated via faeces.
What omeprazole treats
There are many reasons and symptoms that can be relieved by omeprazole. They are:
- It is used to treat stomach and oesophagus problems such as stomach ulcers, acid reflux, etc.
- Omeprazole also provides relieve from heartburn, difficulty swallowing and persistent cough.
- Omeprazole heals up the acid damage caused to the stomach and helps prevent ulcers.
- Omeprazole may help prevent the cancer of oesophagus.
Omeprazole dosing for different age groups
In hyperacidity the dose usually starts with 20mg once a day as an initial therapy and then may be increased to 40mg once a day. Usually patients gets relief within 2 to 4weeks
Adult dose for duodenal ulcers
The usual adult dose for duodenal ulcers are is 20mg once a day 30 to 60minutes before meal. The symptoms are healed between 4 to 8 weeks in average population.
Adult dose for gastric ulcers
The advised dose is 40mg once a day before meals.
Adult dose requirement for Dyspepsia
20mg oral omeprazole is advised to be taken for 14 days before meals.
Side effects of omeprazole
The side effects may be mild, moderate to severe. An individual should get an emergency medical help in case of allergic reactions to omeprazole like hives, difficulty in breathing, swelling of your face, lips, tongue or throat. The side effects should be reported immediately to the doctor or else in emergency call 9-1-1. The common side effects are:
- Gas, stomach pain, abdominal cramps;
- nausea, vomiting, diarrhoea; or
Seek medical help from doctor if conditions worsens with symptoms like:
- seizure ( convulsions)
- dizziness, confusion, tachycardia ( increased heart rate),
- Shaking (tremors) or jerking muscle movements,
- muscle cramps and muscle spasms in your hands and feet,
- Cough or feeling of choking
- Watery diarrhoea and intolerable stomach pain.
Omeprazole and Zollinger- Ellison syndrome
Zollinger-Ellison syndrome is a rare kind of syndrome in which tumours are developed in one or more numbers in your pancreas or the upper part of your small intestine(duodenum). These tumour are known as Gastrinomas, which secret large amount of hormone called gastrin in the body precisely stomach which causes stomach to produce more acid.
Adult dose for Zollinger-Ellison syndrome: Initial: The therapy is started with the 60mg orally once a day and it should be personalized by doctor for every patient as the severity and body to reflect towards the medication are different.
Maintenance dose: Dosing with the maximum of 120mg, 3 times have found to be administered and when the need for dose increases above 80mg should be provided in divided doses.
Can Levothyroxine and omeprazole be taken together
No, levothyroxine and omeprazole can’t be taken together at a time and within a near coarse of time. The site of absorption for both the drugs is same and more over the direction to use levothyroxine and omeprazole are at empty stomach before meals.
However, when omeprazole is taken with levothyroxine the available site for absorption of levothyroxine is occupied with omeprazole such that fewer site is left for levothyroxine to bind and provide its biological effect. This lead to dose adjustment with levothyroxine due to lesser absorption of the drug and not meeting the desired effect.
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