Linezolid Tablets

Mechanism

Linezolid is a synthetic, antibacterial agent that belongs to a new class of antimicrobials, the oxazolidinones. It has in vitro activity against aerobic Gram positive bacteria and anaerobic micro-organisms. Linezolid selectively inhibits bacterial protein synthesis via a unique mechanism of action. Specifically, it binds to a site on the bacterial ribosome (23S of the 50S subunit) and prevents the formation of a functional 70S initiation complex which is an essential component of the translation process.
The in vitro post antibiotic effect (PAE) of linezolid for Staphylococcus aureus was approximately 2 hours. When measured in animal models, the in vivo PAE was 3.6 and 3.9 hours for Staphylococcus aurous and Streptococcus pneumonia, respectively. In animal studies, the key pharmacodynamic parameter for efficacy was the time for which the linezolid plasma level exceeded the minimum inhibitory concentration (MIC) for the infecting organism. Pharmacokinetics

• Absorption: Linezolid is rapidly and extensively absorbed following the dosing. Maximum plasma concentrations are reached within 2 hours of dosing.
• Distribution: Volume of distribution at steady-state averages at about 40-50 litres in healthy adults and approximates to total body water. Plasma protein binding is about 31% and is not concentration dependent.
• Metabolism: Linezolid is primarily metabolised by oxidation of the morpholine ring resulting mainly in the formation of two inactive open-ring carboxylic acid derivatives. The hydroxyethyl glycine metabolite is the predominant human metabolite and is believed to be formed by a non-enzymatic process. The aminoethoxyacetic acid metabolite is less abundant. Other minor, inactive metabolites have been characterised.
• Elimination: In patients with normal renal function or mild to moderate renal insufficiency, Linezolid is primarily excreted under steady-state conditions in the urine.

Side Effects

• Nausea
• Diarrhea
• Headache
• Thrombocytopenia
• Peripheral neuropathy (long-term use)

Contraindication

• Hypersensitivity to Linezolid
• Concurrent use with MAO inhibitors
• Uncontrolled hypertension

Interaction

• SSRIs: Risk of serotonin syndrome
• MAO inhibitors: Hypertensive crisis
• Tyramine-rich foods: Increased blood pressure
• Adrenergic agents: Enhanced pressor response

Warning and Precautions

• Monitor blood counts during prolonged therapy
• Use cautiously in hypertension
• Avoid long-term use due to neuropathy risk
• Monitor for serotonin syndrome