Alendronate Alendronate is a first‑generation, nitrogen‑containing bisphosphonate used primarily to inhibit bone resorption and prevent fractures in osteoporotic and other high‑fracture‑risk patients. Mechanism of Action Alendronate binds to hydroxyapatite in bone and is selectively taken up by osteoclasts during bone‑resorption events. Inside osteoclasts, it inhibits farnesyl diphosphate synthase, blocking the mevalonate pathway and preventing prenylation of … Read more
Albuterol Albuterol (also known as salbutamol) is a short‑acting β₂‑adrenergic agonist widely used as an inhaled bronchodilator for pulmonary conditions. Mechanism of Action β₂‑Receptor Agonist β₂ receptors on bronchial smooth‑muscle → ↑cyclic‑AMP → protein kinase A activation Phosphorylation of myosin light‑chain kinase → inhibition of calmodulin‑dependent contraction Result: rapid, reversible bronchodilation (onset ≤ 5 min, peak 10–15 min) Pharmacokinetics … Read more
Acyclovir Mechanism of Action Selective activation by viral thymidine kinase to acyclovir monophosphate (viral specific). Host cellular kinases convert it to the triphosphate form. The triphosphate competitively inhibits viral DNA polymerase and incorporates into nascent DNA strands, causing chain termination. High selectivity for infected cells reduces host toxicity. Pharmacokinetics Parameter Typical Value Notes Bioavailability 10–30 % … Read more
Acetylcysteine Mechanism of Action Acetylcysteine is a glutathione precursor and a disulfide‑bond reducer. Antidote for acetaminophen (paracetamol) overdose: It is deacetylated in the liver to produce N‑acetyl‑p‑cysteine, which supplies cysteine for glutathione synthesis. Glutathione conjugates hepatotoxic N‑acetyl‑p‑benzoquinone imine, allowing its safe excretion. Mucolytic activity: In mucus, disulfide bonds cross‑link mucin proteins. Acetylcysteine breaks these bonds, … Read more
Acetazolamide Mechanism of Action Carbonic anhydrase inhibitor (enzyme‑specific inhibition of CA II in proximal tubules). ↓Formation of hydrogen ions → ↓Na⁺, HCO₃⁻ reabsorption → increased urinary pH, volume, and chloride excretion. Reduces aqueous humor production by blocking CO₂ ↔ H₂O ↔ H⁺ + HCO₃⁻ conversion in ciliary epithelium, lowering intra‑ocular pressure. Decreases cerebrospinal fluid (CSF) … Read more
Acetaminophen Mechanism of Action Acetaminophen is a centrally acting analgesic and antipyretic whose exact pharmacodynamics are not fully elucidated. The prevailing theory involves: Inhibition of cyclo‑oxygenase (COX) in the brain, with a preferential effect on COX‑2 or on a unique isoform, leading to ↓ prostaglandin synthesis and reduced pain and fever signaling. Modulation of the … Read more
Buspirone Mechanism of Action Buspirone acts primarily as a partial agonist at presynaptic serotonin (5‑HT₁A) receptors in the limbic system. By reducing serotonin release, it modulates anxiety without the GABA‑ergic potentiation seen with benzodiazepines. Additionally, buspirone exhibits low‑affinity antagonism at dopamine D₂ receptors (especially in the mesolimbic pathway) and minimal affinity for muscarinic, adrenergic, or … Read more
Metformin Mechanism of Action Metformin exerts its antihyperglycemic effect primarily through multiple, complementary mechanisms: ↓ Hepatic gluconeogenesis – Inhibits mitochondrial respiratory chain complex I, reducing ATP production and activating AMP‑activated protein kinase (AMPK). AMPK phosphorylates and inactivates phosphoenolpyruvate carboxykinase (PEPCK) and glucose‑6‑phosphatase, suppressing gluconeogenesis. ↑ Peripheral glucose uptake – Enhances GLUT‑4 translocation in skeletal muscle and … Read more
Atropine Mechanism of Action Atropine is a potent, non‑selective antimuscarinic agent that competitively inhibits acetylcholine binding at muscarinic receptors in the parasympathetic nervous system. α‑1‑adrenergic stimulation via muscarinic blockade → peripheral vasoconstriction β‑adrenergic blockade through vagal inhibition → increased heart rate Disinhibition of the tear ducts, salivary glands, and sweat glands → decreased secretions Lipid … Read more
Aspirin Mechanism of Action Aspirin (acetyl‑salicylic acid) irreversibly acetylates serine residues in the active sites of cyclo‑oxygenase enzymes COX‑1 and COX‑2. Inhibition of COX‑1 in platelets ↓ thromboxane A₂ → potent, long‑lasting antiplatelet effect. Inflammatory tissues: COX‑2 inhibition reduces prostaglandin‑mediated pain, fever, and swelling. Low‑dose aspirin (≤100 mg/day) primarily targets platelets; higher doses (≥300 mg) provide additional anti‑inflammatory … Read more