Lansoprazole, Structure, Metabolism, Mechanism Of Action, Drug Interactions, Therapeutic Uses, Side Effects and Contraindications

Lansoprazole 

Lansoprazole is a medication that belongs to a class of drugs known as proton pump inhibitors (PPIs). It is commonly used to treat various conditions related to excess stomach acid production.

Lansoprazole is available under various brand names, depending on the manufacturer and the country. Some common brand names for lansoprazole include:

  1. Prevacid: This is one of the most well-known brand names for lansoprazole. It is available in various formulations, including delayed-release capsules and orally disintegrating tablets.

  2. Prevacid 24HR: This is an over-the-counter (OTC) version of lansoprazole that is available without a prescription. It is used for short-term treatment of frequent heartburn.

  3. Lanzol: Another brand name for lansoprazole used in some countries.

  4. Ogastro: This brand name is used in certain regions for lansoprazole products.

  5. Agopton: Lansoprazole may be marketed under this brand name in some countries.

  6. Lansopril: Another brand name that might be used for lansoprazole.

It's important to note that availability and brand names may vary depending on your location.

Metabolism

Lansoprazole is metabolized primarily in the liver through a process involving the cytochrome P450 (CYP) enzyme system. The main metabolic pathway for lansoprazole involves CYP2C19 and CYP3A4 enzymes. Here's a brief overview of the metabolism of lansoprazole:

  1. CYP2C19 Metabolism: CYP2C19 is the primary enzyme responsible for the metabolism of lansoprazole. It converts lansoprazole into its main metabolites, 5-hydroxylansoprazole and lansoprazole sulfone. These metabolites are less active than the parent drug in terms of inhibiting gastric acid secretion.
  2. CYP3A4 Metabolism: CYP3A4 is another enzyme involved in the metabolism of lansoprazole, albeit to a lesser extent compared to CYP2C19. This enzyme contributes to the formation of 5-hydroxylansoprazole, one of the major metabolites.
  3. Other Metabolic Pathways: In addition to CYP enzymes, lansoprazole can also undergo metabolism through non-enzymatic pathways, including chemical conversion in the stomach.
  4. Genetic Variability: The metabolism of lansoprazole, especially its conversion by CYP2C19, can be influenced by genetic variability. Some individuals may have genetic variations that affect the activity of CYP2C19, leading to differences in the rate at which lansoprazole is metabolized. This can impact the effectiveness and potential side effects of the medication.
  5. Drug Interactions: Since lansoprazole is metabolized by CYP enzymes, it has the potential to interact with other drugs that affect these enzymes. Some medications can inhibit or induce the activity of CYP2C19 and CYP3A4, leading to changes in the metabolism of lansoprazole and other drugs.


Mechanism Of Action

The MOA of Lansoprazole is based on its classification as a proton pump inhibitor (PPI). It primarily works by reducing the production of stomach acid through its action on the proton pumps in the stomach lining. Here's a more detailed explanation of the mechanism of action (MOA) of lansoprazole:

  1. Proton Pumps and Acid Production: Stomach acid plays a crucial role in the digestion of food, but excessive acid production can lead to conditions like gastroesophageal reflux disease (GERD), peptic ulcers, and others. Acid is produced in the stomach by specialized cells called parietal cells. These cells contain proton pumps (proton-potassium pumps) that transport hydrogen ions (protons) into the stomach to generate stomach acid.
  2. Inhibition of Proton Pumps: Lansoprazole inhibits the activity of these proton pumps in the stomach lining. It does this by binding to the proton pumps and blocking their function. This action reduces the secretion of hydrogen ions into the stomach, thereby decreasing the production of stomach acid.
  3. Reduction in Acid Secretion: With reduced activity of proton pumps, the secretion of acid into the stomach is significantly decreased. This helps in alleviating symptoms related to excessive acid production, such as heartburn, acid reflux, and stomach ulcers.
  4. Gastric pH Increase: The decreased acid production leads to an increase in the pH of the stomach, making it less acidic. This change in pH creates a less acidic environment in the stomach, which can aid in healing and preventing damage to the stomach lining in conditions like peptic ulcers.
  5. Duration of Action: Lansoprazole has a relatively long duration of action, which allows for sustained reduction in stomach acid production. This makes it effective for controlling acid-related conditions over an extended period of time.

Drug Interactions

Lansoprazole, like many other medications, can interact with other drugs, potentially affecting their effectiveness or increasing the risk of side effects. It's important to inform your healthcare provider about all the medications, supplements, and herbal products you are taking before starting lansoprazole. Here are some examples of drug interactions with lansoprazole:

  1. Interactions with CYP2C19 Inhibitors: Since lansoprazole is metabolized by the CYP2C19 enzyme, drugs that inhibit this enzyme can potentially increase the levels of lansoprazole in the body. This could lead to an increased risk of side effects. Examples of CYP2C19 inhibitors include fluconazole, citalopram, and certain antiplatelet drugs like clopidogrel.
  2. Interactions with CYP3A4 Inducers and Inhibitors: Lansoprazole is also metabolized by the CYP3A4 enzyme. Drugs that inhibit or induce CYP3A4 can affect the metabolism of lansoprazole. For example, drugs like ketoconazole (inhibitor) and rifampin (inducer) can impact lansoprazole's levels in the body.
  3. Warfarin: Lansoprazole may interact with warfarin, an anticoagulant medication. PPIs like lansoprazole could potentially increase the risk of bleeding when taken concomitantly with warfarin. Close monitoring of blood clotting parameters may be necessary if these medications are used together.
  4. Methotrexate: Lansoprazole might decrease the elimination of methotrexate from the body, potentially increasing the risk of methotrexate-related toxic effects.
  5. Digoxin: Lansoprazole could potentially increase the absorption of digoxin, a medication used for heart conditions, leading to elevated digoxin levels and potential toxicity. Monitoring of digoxin levels may be needed.
  6. Atazanavir: Lansoprazole can reduce the absorption of atazanavir, a medication used to treat HIV infection. Therefore, these two drugs should not be taken simultaneously.
  7. Antiretroviral Medications: Lansoprazole might reduce the absorption of certain antiretroviral medications used to treat HIV.
  8. Clopidogrel: There is a concern that concomitant use of PPIs, including lansoprazole, might reduce the effectiveness of clopidogrel, a medication used to prevent blood clots. Consult your healthcare provider before using these medications together.
This list is not exhaustive, and there may be other potential drug interactions with lansoprazole.


Therapeutic Uses


Lansoprazole is a proton pump inhibitor (PPI) that is used for various therapeutic purposes related to reducing stomach acid production. Here are some of the primary therapeutic uses of lansoprazole:

  1. Gastroesophageal Reflux Disease (GERD): Lansoprazole is commonly prescribed to treat GERD, a condition in which stomach acid flows back into the esophagus, causing symptoms such as heartburn, regurgitation, and chest pain. By reducing stomach acid production, lansoprazole helps alleviate these symptoms and allows the esophagus to heal.
  2. Peptic Ulcers: Lansoprazole is used to treat and prevent peptic ulcers, which are open sores that can develop in the stomach, small intestine, or esophagus. By reducing stomach acid production, lansoprazole promotes the healing of these ulcers and helps prevent their recurrence.
  3. Zollinger-Ellison Syndrome: This is a rare condition characterized by the excessive production of stomach acid due to tumors in the pancreas or duodenum. Lansoprazole can help control and manage the excessive acid production associated with this syndrome.
  4. Erosive Esophagitis: Lansoprazole is prescribed to treat erosive esophagitis, a condition where the lining of the esophagus becomes inflamed and damaged due to stomach acid exposure. By reducing acid production, lansoprazole helps in the healing of the esophageal lining.
  5. Helicobacter pylori Eradication: Lansoprazole is often included in combination therapy regimens to help eradicate Helicobacter pylori, a bacterium that can cause stomach ulcers and gastritis. It is used in combination with antibiotics to help eliminate the infection and promote ulcer healing.
  6. Short-Term Treatment of Heartburn: An over-the-counter version of lansoprazole (Prevacid 24HR) is approved for short-term treatment of frequent heartburn (two or more days a week). It provides relief from heartburn symptoms.


Side Effects

Lansoprazole, like any medication, can potentially cause side effects in some individuals. Not everyone will experience these side effects, and their severity can vary. It's important to discuss potential side effects with your healthcare provider before starting lansoprazole. Here are some common and less common side effects associated with lansoprazole:

Common Side Effects:

  • Headache
  • Diarrhea
  • Nausea
  • Abdominal pain
  • Constipation
  • Gas or bloating
  • Dizziness

Less Common or Serious Side Effects:

  • Allergic reactions (rash, itching, swelling, severe dizziness, difficulty breathing)
  • Bone fractures (especially with long-term use)
  • Clostridium difficile-associated diarrhea (a serious intestinal infection)
  • Vitamin B12 deficiency (with long-term use)
  • Low magnesium levels (can lead to muscle spasms, irregular heartbeat, seizures)
  • Kidney problems
  • Liver problems
  • Increased risk of certain infections, such as pneumonia
  • Increased risk of stomach polyps (with long-term use)
Lansoprazole is usually well-tolerated, and many people do not experience significant side effects.

Contraindications

Contraindications are specific situations or conditions in which a medication should not be used due to potential risks or adverse effects. For lansoprazole, there are certain contraindications that individuals and healthcare providers should be aware of before using the medication. Here are some contraindications for lansoprazole:

  1. Hypersensitivity to Lansoprazole: Individuals who have a known hypersensitivity or allergic reaction to lansoprazole or any of its components should not use this medication.
  2. Hypersensitivity to Other Proton Pump Inhibitors (PPIs): Individuals who are hypersensitive or allergic to other PPIs should exercise caution when using lansoprazole, as cross-reactivity is possible.
  3. Atazanavir Use: The coadministration of lansoprazole with atazanavir, a medication used to treat HIV, is contraindicated due to a significant reduction in the absorption of atazanavir when taken with PPIs like lansoprazole.
  4. Combination with Rilpivirine: The coadministration of lansoprazole with rilpivirine, another HIV medication, is contraindicated, as it can reduce the absorption of rilpivirine and potentially affect its effectiveness.
  5. Use with Erlotinib: Lansoprazole can reduce the absorption of erlotinib, a medication used in cancer treatment, potentially affecting its efficacy. The use of these two drugs together should be avoided.
  6. Clopidogrel Interaction: While not an absolute contraindication, there is a concern that the concomitant use of PPIs like lansoprazole may reduce the effectiveness of clopidogrel, a medication used to prevent blood clots. Healthcare providers should carefully consider the risks and benefits when prescribing these medications together.
  7. Pregnancy and Breastfeeding: The use of lansoprazole during pregnancy and breastfeeding should be discussed with a healthcare provider, as potential risks and benefits need to be evaluated.
It's important to note that the decision to use or avoid lansoprazole based on contraindications should be made in consultation with a qualified healthcare provider.

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