Introduction Senna is a stimulant laxative derived from the leaves and pods of Senna species plants. It is commonly used for short-term treatment of constipation and bowel evacuation before diagnostic procedures. Senna acts mainly in the colon by stimulating intestinal motility and increasing water secretion into the bowel lumen. Mechanism of Action (Step-wise) A key … Read more
Introduction Selegiline is a selective monoamine oxidase-B (MAO-B) inhibitor primarily used in Parkinson disease. It increases dopamine availability in the central nervous system by inhibiting dopamine metabolism. At higher doses, selectivity for MAO-B decreases and inhibition of MAO-A may also occur. Selegiline helps improve motor symptoms and may reduce fluctuations in Parkinson disease. Mechanism of … Read more
Introduction Scopolamine is an antimuscarinic drug primarily used for prevention of motion sickness and postoperative nausea and vomiting. It acts by blocking muscarinic acetylcholine receptors in the central and peripheral nervous systems. Scopolamine has significant effects on the vestibular system and vomiting center, making it especially useful in motion-related nausea. Mechanism of Action (Step-wise) A … Read more
Introduction Rosuvastatin is a statin medication used to treat hypercholesterolemia and reduce cardiovascular risk. It lowers low-density lipoprotein (LDL) cholesterol by inhibiting hepatic cholesterol synthesis. Rosuvastatin is one of the most potent HMG-CoA reductase inhibitors and is widely used in prevention of atherosclerotic cardiovascular disease. Mechanism of Action (Step-wise) A key exam point is that … Read more
Introduction Rivastigmine is a centrally acting cholinesterase inhibitor used primarily in Alzheimer disease and Parkinson disease-associated dementia. It improves cognitive function by increasing acetylcholine levels in the brain. Rivastigmine inhibits both acetylcholinesterase and butyrylcholinesterase enzymes, enhancing cholinergic neurotransmission in cortical and hippocampal regions involved in memory and cognition. Mechanism of Action (Step-wise) A key exam … Read more
Introduction Ritalin is the brand name for methylphenidate, a central nervous system stimulant primarily used in attention-deficit/hyperactivity disorder (ADHD) and narcolepsy. It improves attention, concentration, and behavioral control by increasing dopamine and norepinephrine activity in the brain, especially in the prefrontal cortex. Mechanism of Action (Step-wise) A key exam point is that methylphenidate blocks dopamine … Read more
Introduction Risperidone is an atypical antipsychotic medication used in schizophrenia, bipolar disorder, irritability associated with autism spectrum disorder, and other psychiatric conditions. It works mainly through antagonism of dopamine and serotonin receptors in the central nervous system. Compared with typical antipsychotics, risperidone has lower extrapyramidal toxicity at therapeutic doses because of its combined serotonin-dopamine antagonistic … Read more
Introduction Rifaximin is a poorly absorbed rifamycin antibiotic primarily used for gastrointestinal infections and disorders. It acts locally within the gastrointestinal tract and is commonly prescribed for traveler’s diarrhea, hepatic encephalopathy, and irritable bowel syndrome with diarrhea (IBS-D). Rifaximin inhibits bacterial RNA synthesis, leading to suppression of intestinal bacterial growth. Mechanism of Action (Step-wise) A … Read more
Introduction Rifampicin, also known as rifampin, is a bactericidal antibiotic primarily used in the treatment of tuberculosis and other mycobacterial infections. It belongs to the rifamycin class and acts by inhibiting bacterial RNA synthesis. Rifampicin is an essential first-line antitubercular drug and is also used in prophylaxis against meningococcal and Haemophilus influenzae infections. Mechanism of … Read more
Introduction Ribavirin is a broad-spectrum antiviral drug used in combination therapy for chronic hepatitis C infection and in certain viral respiratory infections such as respiratory syncytial virus (RSV). It is a synthetic guanosine analog that interferes with viral RNA synthesis and replication through multiple mechanisms. Mechanism of Action (Step-wise) A key exam point is that … Read more
