Introduction Physostigmine is a reversible acetylcholinesterase inhibitor that increases acetylcholine levels at cholinergic synapses. Unlike quaternary ammonium anticholinesterases, physostigmine is a tertiary amine and can cross the blood-brain barrier, allowing central nervous system effects. It is commonly used in the treatment of anticholinergic toxicity. Mechanism of Action (Step-wise) A key exam point is that physostigmine … Read more
Introduction Phenylephrine is a selective α1-adrenergic receptor agonist used as a vasopressor, nasal decongestant, and mydriatic agent. It produces vasoconstriction by stimulating α1 receptors on vascular smooth muscle. Due to its minimal β-adrenergic activity, phenylephrine primarily affects vascular tone with little direct effect on the heart. Mechanism of Action (Step-wise) A key exam point is … Read more
Introduction Phentermine is a sympathomimetic amine used as an appetite suppressant in the short-term management of obesity. It acts primarily on the central nervous system to reduce hunger and increase satiety. Phentermine is structurally similar to amphetamines and is commonly prescribed along with dietary modification and exercise in weight reduction programs. Mechanism of Action (Step-wise) … Read more
Introduction Phenobarbital is a long-acting barbiturate used primarily as an anticonvulsant and sedative-hypnotic. It is widely used in the management of generalized tonic-clonic seizures and status epilepticus. Phenobarbital enhances inhibitory neurotransmission in the central nervous system, leading to decreased neuronal excitability and seizure control. Mechanism of Action (Step-wise) A key exam point is that phenobarbital … Read more
Introduction Pepto-Bismol contains bismuth subsalicylate, an over-the-counter medication used for the treatment of diarrhea, dyspepsia, nausea, and upset stomach. It has multiple mechanisms of action including antimicrobial, anti-secretory, and mucosal protective effects. Its combination of bismuth and salicylate components contributes to its broad therapeutic activity in gastrointestinal disorders. Mechanism of Action (Step-wise) A key exam … Read more
Introduction Pepcid is the brand name for famotidine, a histamine H2 receptor antagonist used to reduce gastric acid secretion. It is commonly used in conditions such as gastroesophageal reflux disease (GERD), peptic ulcer disease, and dyspepsia. Famotidine works by blocking histamine-mediated stimulation of acid secretion in gastric parietal cells. Mechanism of Action (Step-wise) A key … Read more
Introduction Pentoxifylline is a hemorheologic agent used to improve blood flow, particularly in peripheral vascular diseases such as intermittent claudication. It enhances microcirculation by improving red blood cell flexibility and reducing blood viscosity. Unlike classic vasodilators, pentoxifylline primarily acts by modifying blood rheology and cellular properties. Mechanism of Action (Step-wise) A key exam point is … Read more
Introduction Pantoprazole is a proton pump inhibitor (PPI) used in the treatment of acid-related disorders such as gastroesophageal reflux disease (GERD), peptic ulcer disease, and Zollinger–Ellison syndrome. It reduces gastric acid secretion by irreversibly inhibiting the proton pump in gastric parietal cells. Pantoprazole is highly effective in reducing both basal and stimulated acid secretion. Mechanism … Read more
Introduction Oxymetazoline is a topical decongestant and vasoconstrictor commonly used in nasal sprays and ophthalmic preparations. It is an imidazoline derivative that acts on adrenergic receptors to reduce mucosal congestion. It provides rapid relief in conditions such as allergic rhinitis, sinusitis, and nasal congestion. Mechanism of Action (Step-wise) A key exam point is that oxymetazoline … Read more
Introduction Opiates are a class of drugs derived from opium that produce potent analgesic effects. They act primarily on opioid receptors in the central and peripheral nervous system to relieve pain, produce sedation, and induce euphoria. Common examples include morphine, codeine, and heroin. Opiates are widely used for moderate to severe pain but are associated … Read more
