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Mechanism of Action

Mechanism of Action of Tetracyclines (Broad-Spectrum 30S Ribosome Inhibitors)

Tetracycline MOA – 30S ribosome binding and tRNA blocking

Introduction Tetracyclines are a class of broad-spectrum bacteriostatic antibiotics that inhibit bacterial protein synthesis. Common examples include tetracycline, doxycycline, minocycline, and demeclocycline. They are effective against a wide variety of Gram-positive, Gram-negative, and atypical organisms, including Rickettsia, Chlamydia, Mycoplasma, and Borrelia. Due to their broad usage and distinct mechanism, tetracyclines are high-yield topics for USMLE, … Read more

Mechanism of Action of Aminoglycosides

Aminoglycoside MOA – 30S ribosomal subunit binding and mRNA misreading

Introduction Aminoglycosides are potent bactericidal antibiotics used mainly against aerobic Gram-negative bacilli and serious systemic infections. Common examples include gentamicin, amikacin, tobramycin, streptomycin, and neomycin. Unlike most protein synthesis inhibitors, aminoglycosides are bactericidal, not bacteriostatic. They bind to the 30S subunit of the bacterial ribosome and cause misreading of mRNA, leading to faulty protein synthesis … Read more

Mechanism of Action of Macrolides (Protein Synthesis Inhibitor Antibiotics)

Macrolide MOA – 50S ribosome binding and protein synthesis inhibition

Introduction Macrolides are a widely used class of bacteriostatic antibiotics that inhibit bacterial protein synthesis. They are especially effective against Gram-positive cocci, atypical organisms, and some Gram-negative pathogens. Common macrolides include erythromycin, azithromycin, and clarithromycin. Their use extends to respiratory tract infections, STDs, and skin infections, with azithromycin being a favorite due to its long … Read more

Mechanism of Action of Cephalosporins (β-Lactam Antibiotics)

Cephalosporin MOA – PBP inhibition and bacterial cell wall lysis

Introduction Cephalosporins are a large group of β-lactam antibiotics, structurally and functionally similar to penicillins. They are classified into five generations, each with expanding coverage against Gram-negative organisms and β-lactamase-producing bacteria. Like penicillins, their core mechanism involves inhibition of bacterial cell wall synthesis, making them bactericidal. They are high-yield in USMLE, NCLEX, GPAT, and NEET-PG, … Read more

Mechanism of Action of Penicillins (β-lactam Antibiotics)

Penicillins MOA – Cell wall synthesis inhibition

Introduction Penicillins are one of the oldest and most widely used classes of antibiotics, belonging to the β-lactam family. They’re highly effective against Gram-positive bacteria and some Gram-negatives, depending on the type. Their mechanism centers on inhibiting bacterial cell wall synthesis, which leads to bacterial lysis and death. Penicillins remain a foundational topic for USMLE, … Read more

Mechanism of Action of Lacosamide (Newer Antiepileptic Drug)

Lacosamide MOA – Enhances slow inactivation of sodium channels in epilepsy

Introduction Lacosamide is a newer-generation antiepileptic drug (AED) used for the treatment of focal (partial) seizures and adjunctive therapy for generalized seizures. It has a novel mechanism, targeting slow inactivation of voltage-gated sodium channels, which differentiates it from older AEDs. It is well tolerated and commonly prescribed in the US for both adults and children. … Read more

Mechanism of Action of Gabapentin

Gabapentin MOA – calcium channel modulator in epilepsy and neuropathic pain

Introduction Gabapentin is an antiepileptic drug and one of the most widely prescribed medications for neuropathic pain, postherpetic neuralgia, and partial seizures. Originally developed as a GABA analog, it surprisingly does not act directly on GABA receptors. Instead, it binds to voltage-gated calcium channels, altering neurotransmitter release. It is also used off-label for conditions like … Read more

Mechanism of Action of Ethosuximide

Ethosuximide MOA – T-type calcium channel blocker for absence seizures

Introduction Ethosuximide is the first-line drug for treating absence seizures, a type of generalized seizure common in children. It is uniquely effective due to its action on T-type calcium channels in thalamic neurons, which are critical for the pathophysiology of absence seizures. Unlike most other AEDs, ethosuximide is not effective for other seizure types. It … Read more

Mechanism of Action of Topiramate

Topiramate MOA – GABA enhancer, AMPA blocker, sodium channel inhibitor

Introduction Topiramate is a broad-spectrum antiepileptic drug (AED) known for its use in treating partial and generalized seizures, migraine prophylaxis, and Lennox-Gastaut syndrome. It has a multi-modal mechanism, acting on sodium channels, GABA-A receptors, glutamate receptors, and carbonic anhydrase. Its wide range of targets makes it effective in both epilepsy and mood disorders, though side … Read more

Mechanism of Action of Phenytoin

Phenytoin MOA – voltage-gated sodium channel blocker

Introduction Phenytoin is one of the oldest and most widely used antiepileptic drugs (AEDs), primarily for treating focal seizures and generalized tonic-clonic seizures. It has a well-known profile, acting on voltage-gated sodium channels to reduce high-frequency neuronal firing. Despite newer alternatives, phenytoin remains important, especially in emergency settings like status epilepticus (IV use). It’s a … Read more

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