Digoxin slows conduction through the AV node and increases vagal tone, making it effective in controlling ventricular response in atrial fibrillation.

Penicillin is bactericidal as it disrupts bacterial cell wall synthesis, leading to lysis, whereas tetracycline and chloramphenicol are bacteriostatic.

Epinephrine acts on alpha and beta receptors to counteract the severe hypotension, bronchospasm, and swelling seen in anaphylaxis.

Sulfonylureas (e.g., glimepiride) block ATP-sensitive K⁺ channels in beta cells, leading to depolarization and insulin release.

Phenytoin can cause gingival hyperplasia due to its effect on fibroblast activity, leading to excessive gum tissue growth.

Loop diuretics (e.g., furosemide) inhibit the Na⁺/K⁺/2Cl⁻ co-transporter in the thick ascending limb of the loop of Henle, causing profound diuresis.

Lisinopril is an active drug, unlike enalapril (converted to enalaprilat), codeine (converted to morphine), and levodopa (converted to dopamine in the brain).

Atropine, an anticholinergic drug, counteracts the effects of excess acetylcholine at muscarinic receptors, which is a hallmark of organophosphate poisoning.

Celecoxib selectively inhibits cyclooxygenase-2 (COX-2), reducing inflammation while minimizing gastrointestinal side effects associated with non-selective COX inhibitors.

Beta-blockers work by inhibiting beta-adrenergic receptors (β1 and β2), reducing heart rate and myocardial contractility, and are used in conditions like hypertension and arrhythmias.