OMEMARK-20

Indications

• Gastric ulcer
• Duodenal ulcer
• Gastro-oesophageal reflux disease (GERD)
• Severe oesophagitis
• Helicobacter pylori eradication (in combination therapy)
• Prevention of NSAID-associated gastric and duodenal ulcers
• Zollinger-Ellison syndrome

Dosage

Adults: The usual dose for adults is 20 mg once daily for 4 weeks for duodenal ulcer and GERD. For gastric ulcer, the dose may be 20 mg to 40 mg once daily

Mechanism of action

Omeprazole works by specifically binding to the proton pump (H+/K+ ATPase) in the gastric parietal cells, leading to irreversible inhibition of acid secretion. This binding prevents the exchange of hydrogen ions for potassium ions, effectively reducing the production of gastric acid and promoting healing of acid-related conditions.

Pharmacodynamics

The pharmacodynamic effects of omeprazole manifest as a significant decrease in gastric acidity, which improves symptoms related to excessive acid secretion. The onset of action typically occurs within an hour of administration, with maximum effect seen within 2 to 4 days of continuous use. The duration of action allows for once-daily dosing in most indications.

Pharmacokinetics

Omeprazole is rapidly absorbed from the gastrointestinal tract, reaching peak plasma concentrations within 0.5 to 3.5 hours after oral administration. It is extensively metabolized in the liver via the cytochrome P450 system, primarily CYP2C19 and CYP3A4, leading to the formation of inactive metabolites. The elimination half-life is approximately 0.5 to 1 hour, but the effects on gastric acid secretion last much longer due to the irreversible nature of proton pump inhibition. Omeprazole is excreted mainly in the urine as metabolites, with less than 1% of the drug excreted unchanged.

Contra-indications

• Hypersensitivity to omeprazole or any component of the formulation
• Use with caution in patients with severe liver impairment

Adverse effects

• Nausea
• Vomiting
• Diarrhea
• Headache
• Abdominal pain
• Flatulence
• Constipation
• Dizziness
• Fatigue
• Rash
• Muscle weakness
• Gastrointestinal candidiasis
• Aggression
• Agitation
• Bronchospasm
• Encephalopathy

Interactions

• Cenobamate may increase exposure to omeprazole
• Fedratinib may increase exposure to omeprazole
• Apalutamide may decrease exposure to omeprazole
• Cilostazol may increase exposure to omeprazole

Precautions

• Monitor patients for gastrointestinal symptoms
• Use caution in patients with a history of liver disease
• Consider potential for vitamin B12 deficiency with long-term use
• Monitor for signs of Clostridium difficile infection in the colon

Pregnancy

Not known to be harmful during pregnancy, but should be used only if clearly needed.

Breast-feeding

Excreted in breast milk, caution is advised when administered to nursing mothers.

Storage

Store below 25 degrees Celsius. Protect from moisture. Keep out of reach of children.

Formulations

• Orodispersible tablets
• Gastro-resistant capsules
• Intravenous injection
• Oral suspension

Indications

• Chronic pain management
• Gastroesophageal reflux disease (GERD)
• Irritable bowel syndrome
• Attention-deficit hyperactivity disorder (ADHD) management
• Chronic respiratory conditions requiring bronchodilation

Dosage

Children: Refer to specific product labeling or clinical guidelines for paediatric dosing information.

Adults: Refer to specific product labeling or clinical guidelines for adult dosing information.

Mechanism of action

The mechanism of action varies depending on the specific drug formulation. Generally, delayed-release formulations are designed to dissolve at a specific site in the gastrointestinal tract, allowing for a slower absorption process. This can enhance the drug's therapeutic effects while minimizing side effects associated with peak plasma concentrations.

Pharmacodynamics

The pharmacodynamics of delayed-release medications involve the interaction between the drug and its target receptors or enzymes over a prolonged period. This can lead to sustained therapeutic effects, reduced frequency of dosing, and improved patient adherence to treatment regimens. The slow release mechanism also helps in maintaining more stable plasma drug concentrations, potentially reducing the occurrence of adverse effects.

Pharmacokinetics

Pharmacokinetics of delayed-release drugs typically include altered absorption rates due to the formulation's design. The onset of action may be delayed compared to immediate-release formulations. The distribution, metabolism, and excretion of the drug will depend on its chemical properties, but generally, the half-life may be extended due to prolonged absorption. Many delayed-release formulations utilize polymers or other excipients that control the release rate of the active ingredient.

Pregnancy

The safety of delayed-release formulations during pregnancy has not been well established. Consultation with a healthcare provider is recommended.

Breast-feeding

Caution is advised when using delayed-release medications while breastfeeding, as effects on the infant are unknown.

Storage

Store at room temperature, away from moisture and direct sunlight. Keep out of reach of children.

Indications

• Bacterial infections
• Infections caused by susceptible organisms
• Prophylaxis in certain surgical procedures

Dosage

Children: Refer to the BNF for Children for specific dosing recommendations based on age, weight, and condition.

Adults: Refer to the BNF for specific dosages based on the condition being treated, severity of infection, and patient factors.

Mechanism of action

Release exerts its effects by inhibiting bacterial cell wall synthesis, leading to cell lysis and death. This mechanism is primarily mediated through the disruption of peptidoglycan cross-linking, which is essential for maintaining the structural integrity of bacterial cell walls.

Pharmacodynamics

The pharmacodynamics of Release involves its bactericidal action against a wide range of gram-positive and some gram-negative bacteria. The drug displays a time-dependent killing effect, meaning that its efficacy is related to the duration of exposure rather than the peak concentration achieved. Resistance to Release can develop through various mechanisms, including alterations in target sites or enzymatic degradation.

Pharmacokinetics

Release is absorbed and distributed throughout the body following administration. Peak plasma concentrations are typically achieved within a few hours. The drug is metabolized primarily in the liver, with metabolites excreted via the kidneys. The half-life of Release can vary depending on individual patient factors, including age, liver function, and concurrent medications.