Pharmacology

Psychopharmacology is a branch of Pharmacology and psychiatry that deals with medications used to treat mental disorders. This field has come a long way in recent years, and many effective treatments are now available for mental illnesses. The study of medications and their effects on the human body is pharmacology, and the study of drugs only treating mental disorders is known as Psychopharmacology.  Every day some discoveries help us understand how these drugs work, allowing medical experts to better treat mental disorders with an improved understanding of the mechanism of medicines on our brain and nerve system. So, psychopharmacology is the scientific study of how different drugs affect mood, sensation, and thinking. Anyone who studies the effects of psychotropic drugs on the human brain is known as Psychopharmacologist. Psychopharmacologists need to understand all the clinically relevant principles of pharmacokinetics, and pharmacodynamics, such as protein binding half-life, which can vary greatly depending on everyone’s genes, mechanism of action of all psychotropic drugs, and interactions between different medications. The use and application of psychoactive substances have been used throughout history. Still, it’s only recently that these applications have attained the same level as scrutiny given to lab-made compounds. The term “psychopharmacology” was likely coined by David Macht in the 1920s when he introduced this new field that studied how different drugs affect brain function. Psychopharmacologists should understand basic concepts like how these psychoactive drugs work. This article will specifically discuss Neurotransmitters and Hormones because these drugs work by acting on them. Neurotransmitter Neurotransmitters are the messengers of our body’s systems. They are endogenous chemicals that allow signals to be passed between cells in different parts or organs while transmitting information from one cell type (such as muscle) to another through these receptor channels. Communication between two neurons happens in the synaptic cleft (the small gap between the synapses of neurons). The brain needs neurotransmitters like dopamine and serotonin because they regulate many important functions, including heart rate and many other functions. Modern Psychopharmacology is largely due to advances in our understanding of chemical neurotransmission. Knowing about chemical neurotransmission is essential if you truly want to understand how drugs impact our brains. Some of the most popular psychoactive drugs affect neurotransmitters and can be viewed as chemicals through which neurons primarily communicate. Following are some of the mechanisms by which psychoactive drugs affect the Neurotransmitter; One way they do this is by serving as a precursor for the Neurotransmitter; Others include the blocking of neurotransmitter production, Some drugs are also responsible for preventing the storage of neurotransmitters in the presynaptic vesicle. They can also wholly activate or inhibit the release of neurotransmitters, Sometimes they can restore or block the post-synaptic receptors, Primarily inhibit neurotransmitter reuptake by the presynaptic neuron. Psychoactive drugs almost exert their mind-altering effects by acting on these neurotransmitters and modifying one or more aspects of synaptic transmission. Here is a list of essential neurotransmitters affected by psychotropic drugs; Acetylcholine—this Neurotransmitter is involved in the body’s learning, memory, and mood. It’s a part of the autonomic nervous system that contracts smooth muscles, increases bodily secretions, dilates blood vessels, and slows the heart rate. Dopamine— is another neurotransmitter in motor circuits for reward and pleasure centers. This one is also involved in Parkinson’s Disease and Schizophrenia. GABA (Gamma Amino Butyric Acid)—This NT involves anxiety, epilepsy, fear, stress, and inhibitory neurotransmitter diseases. It blocks impulses between nerve cells in the brain; a low level of this NT can cause chronic pain, anxiety, and epilepsy.  Glutamate— is an amino acid and one of the brain’s most commonly found excitatory neurotransmitters. It helps in learning, memory, communication, and excitatory neurotransmitter diseases. Norepinephrine—(another name is Noradrenaline) is a naturally occurring chemical in the body that acts as a stress hormone and Neurotransmitter. The adrenal medulla in the human brain produces this hormone in reaction to low BP as it cause constriction of blood vessels, that’s why it causes an increase in blood pressure. Too much of this Neurotransmitter can cause anxiety, high blood pressure, increased heart rate, stress, and sleep disturbances. Norepinephrine can be crucial in your body’s “fight-or-flight” response. Serotonin— Also known as 5HT, is a monoamine neurotransmitter primarily found in the digestive system but involved in aggression, wound healing, bone health, depression, desire, mood, sleep, schizophrenia, and sexual desire. Hormones Hormones are secreted by endocrine glands into the bloodstream and convey messages within the body to act on the distant target cells. At the same time, the neurotransmitters are secreted by nerve cells in the brain and travel across the synapse to act on the nearby cells. Hormones work slowly, over time, affecting many different processes like growth, development, and metabolism, while the Neurotransmitter is fast and short-acting.  Psychoactive drugs can also work by affecting the communication between cells through hormones. Hormones and neurotransmitters work in very different ways. Neurotransmitters can only travel a microscopic distance before reaching their target at the other side of your synaptic cleft. At the same time, hormones often have long-distance traveling abilities that allow them to reach cells anywhere throughout our bodies. Here is how the psychoactive drugs work on hormones; Psychotropic medications can change the secretion of many hormones; Hormones may also improve the behavioral responses to drugs. Some hormones themselves sometimes have psychoactive properties; and The secretion of some hormones, mainly those dependent on the pituitary gland, is controlled by neurotransmitter systems in the brain. Psychotropic Medication/Drugs Psychopharmacology [1] can be further classified into many different classes of psychotropic medications. In this section of the article, we will discuss them one by one; Antidepressants Antidepressants are a class of medications that can relieve symptoms in people who suffer from depression, social anxiety disorder, or other conditions. Antidepressants are a medication that has been used for over 50 years. They’re increasingly popular these days, too. These drugs can cause various side effects, including tremors, sleep disturbances, Nausea, nervousness, and sexual problems.  The list of medications for depression is further classified into many different groups of drugs like SSRIs, SNRIs, Tricyclic antidepressants, MAO inhibitors, and Noradrenaline

The field of pharmacology is highly respected throughout the world. It requires years of training, extending from undergraduate studies to graduate studies. The average pharmacologist spends a decade to twelve years in college learning about pharmaceuticals. Even after they have graduated, they must pass an examination administered by their state to be licensed and work as a pharmacologist. Knowing what is in store for them commitment-wise is important as it allows them to put the time and money into preparing for a rewarding career in pharmacology. Researching the field and knowing what it takes to pass their licensing exam is imperative to their success. Students who take the time to explore requirements outside of their degrees have the upper hand because they know what their next steps are in their career paths. This short guide explains the advantages of becoming a pharmacologist including salary information and what niches exist within the career field. It also mentions the best ways to prepare for the USMLE exam and the graduate’s first job in the industry. It serves as a resource that can be reviewed as many times as needed to prepare for a successful pharmacology career. What becoming a pharmacologist can do for you? Jobs in the medical field are always in high demand. Pharmacologists provide valuable insight into the industry through the services they provide. Pharmaceuticals are lifesaving medications administered to people with a myriad of physical and mental health issues that need treatment. 1. Provides you with a competitive salary and benefits package based on your experience. A pharmacologist can earn over $118,000 as an average base salary. It depends mostly on which company they choose to work for and the number of years of experience they have working in the industry. SalaryExpert.com reports that entry-level pharmacologists can make $82,900, and experienced professionals make up to $147,674. The perks that come with being a pharmacologist are well-documented. In addition to providing you with job security, a competitive salary, and full benefits package, working in the field of pharmacology allows you to fulfill your personal goal of helping people be well. Thanks to your extensive knowledge of pharmaceuticals, you’re able to play a role in your customers’ health regimens. 2. Allows you to narrow your focus to the niche of your choice. Furthermore, you can go into whichever niche interests you, thanks to the diverse field of pharmacology. Behavioral pharmacology is one very enticing option because it studies the effects of drugs on a person’s behavior and how their behavior affects the effectiveness of the pharmaceuticals taken. Biochemical pharmacology studies the chemicals that makeup drugs and how they interact with one another and the brain. 3. Lets you work alone or with others in an environment that promotes growth. Pharmacologists have the option of working alone by starting their own pharmacies or working with other skilled individuals who share a passion for the field of pharmacology. If you love challenges, you’ll enjoy the environment created for you at pharmacological companies nationwide. Advancement opportunities exist for professionals who want to make pharmacology their lifetime careers. If you’re looking for a rewarding profession and want to explore the field of pharmacology, you’ll find researching schools, curriculum, and licensing requirements imperative to your success. Knowing what type of education to pursue and where to get it from helps set you up for success come test time. To practice in any state in the nation, you must pass the USMLE exam to work as a pharmacologist. How students prepare for the USMLE at home? Difficult exams such as the USMLE require extra preparation. Students of pharmacology often rely on online technologies as part of their study routine. They use USMLE exam prep sites to access guides and take practice tests as a way to prepare for their official exam date and time. Many options to choose from, but one that stand from the rest is Lecturio, with their spaced-repetition techniques, an evidence-based learning technique that is usually performed with flashcards designed to enhance cognitive memory of students Having the opportunity to prepare for the examination at home is highly beneficial. It allows students to schedule study time into their current schedules with greater ease. With flexible sessions, they can work around the other obligations in their life without missing opportunities to study for the USMLE. They can also form virtual study groups that allow them to review key concepts and terminology online through streaming services. Facebook Messenger, Zoom, and Skype offer options where students can see and interact with one another while they prepare for the exam they need to take to become pharmacologists. The more time a student puts into studying for the USMLE, the better. Using the tools and resources available for them to choose from gives them a distinct advantage in successfully passing the test. Exam prep sites, printed materials, and study buddies all play a crucial role in the success of the pharmacology student. A rewarding career awaits you as a pharmacologist. A degree in pharmacology has its advantages. Each offers you the opportunity to succeed in a high-demand field full of talented and driven professionals. As a student, you have the opportunity to join an industry with growth opportunities galore. Once you’ve passed your exam, you’ll be able to find work in the niche of your specialty. Being able to help people with a myriad of health conditions is highly beneficial. Knowing that you’ve also chosen a profession with growth opportunities is very exciting. You can start your career making entry-level wages and, within a few short years, be commanding a significantly higher salary based on your experience as a senior pharmacologist.

What is Pharmacology?: Definition | Basic Concept | Branches What is Pharmacology? The Complete Guide to Understanding Drug Science Discover why pharmacology is the cornerstone of modern medicine—from how your morning coffee affects your brain to why medications work differently for each person. This comprehensive guide reveals the fascinating science behind every pill, injection, and treatment you encounter. PRIMARY AUTHOR Manzoor Khan Pharmacist with a decade of experience in supplements & health writing 📝 📘 🐦 💼 MEDICAL REVIEWER Dr. Sajid Ali Pharm D, MPhil, PhD Scholar in Pharmacognosy 📝 Published: November 22, 2025 | Last Updated: November 22, 2025 Pharmacology stands as the cornerstone of modern medicine and pharmacy practice. Whether you’re a student beginning your journey in healthcare, a practicing professional seeking to refresh your knowledge, or simply curious about how medications work in your body, understanding pharmacology is essential. In this comprehensive guide, you’ll discover what pharmacology truly means, explore its fundamental concepts and definitions, understand how drugs interact with living organisms, and learn about the diverse branches that make this field so fascinating and crucial to healthcare. Let’s embark on this journey through one of medicine’s most important disciplines. What is Pharmacology? Understanding the Foundation Etymology and Core Definition: The word pharmacology derives from two Greek words: pharmacon meaning “drug” and logy meaning “study.” At its core, pharmacology is the comprehensive study of drugs and their interactions with living organisms. This branch of medical science encompasses drug design, mechanisms of action, therapeutic applications, and clinical use. The field covers an extensive range of topics, including: How drugs affect body systems and cellular function The mechanisms by which drugs produce therapeutic effects Development and testing protocols for new medications Optimization of drug therapy for individual patients Understanding and preventing harmful drug effects (toxicology) Improving medication safety and efficacy Identifying novel treatments for diseases Comprehensive Definitions from Multiple Perspectives Clinical Definition: Pharmacology is the study of how medicinal substances interact with living systems to produce therapeutic effects. Academic Definition: The branch of medical and pharmaceutical science dealing with the nature, sources, properties, absorption, distribution, biotransformation, elimination, interactions, toxicology, and therapeutic applications of drugs. Practical Definition: The study of the body’s reaction to drugs and how medications can be optimized for patient care. Scientific Definition: The integrated study of pharmacokinetics and pharmacodynamics—the two main pillars of this discipline. The Scope and Importance of Pharmacology Modern pharmacology sits at the intersection of biomedical science, combining principles from chemistry, physiology, pathology, molecular biology, and clinical medicine. Pharmacologists—experts in this field—work collaboratively across multiple disciplines including: Neuroscience and behavioral medicine Molecular and cellular biology Immunology and infectious diseases Cancer biology and oncology Cardiovascular and metabolic research These professionals play a crucial role in discovering new medications, improving drug effectiveness, and reducing unwanted adverse effects. According to the National Institutes of Health, pharmacology research continues to advance our understanding of drug safety and efficacy in 2025. Pharmacology vs. Pharmacy: Clarifying the Distinction Many people confuse these related but distinct fields: Pharmacology is a scientific discipline focused on drug research, discovery, and understanding cellular and organic functions of chemical substances. It’s the theoretical foundation. Pharmacy is a healthcare profession representing the practical application of pharmacological principles. Pharmacists use the knowledge gained from pharmacology to formulate, dispense, and counsel patients about medications. Think of it this way: pharmacology provides the “why” and “how” of drug action, while pharmacy delivers the “what” and “when” of medication use in patient care. If you’re interested in learning more about the breadth of this field, explore our comprehensive guide to the whole pharmacology classification. Understanding Drugs: The Foundation of Pharmacology What Exactly is a Drug? Before diving deeper into pharmacology, we must clearly define what constitutes a drug: A drug is any chemical entity that causes a change in biological function in a living organism. It can be any chemical substance used for the diagnosis, prevention, and treatment of diseases. Drugs can originate from two primary sources: Endogenous drugs: Substances formed naturally within the body, such as insulin, noradrenaline (norepinephrine), and various hormones. Xenobiotics: Human-made or natural substances introduced from outside the body—this includes virtually all medications you take orally, by injection, or through other routes. Examples include common medications like acetaminophen (paracetamol), antibiotics, and blood pressure medications. For a practical understanding of commonly encountered medications, refer to our detailed list of the top 101 most commonly used drugs. How Do Drugs Actually Work? The mechanism of drug action represents one of pharmacology’s most fascinating aspects. Drugs generally work through two primary mechanisms: Receptor Interaction: Drugs bind to specific receptors on cell surfaces, triggering a cascade of cellular responses. Enzyme Modulation: Drugs interact with enzymes within cells, either enhancing or inhibiting their activity. Both drug binding sites and enzyme molecules possess a specific three-dimensional structure—like a lock and key system—that allows only molecules with precisely matching shapes to attach to them. The Receptor Concept: A Fundamental Principle What is a Receptor? A drug receptor is a specialized target area that binds to a drug molecule and mediates its pharmacological effects. These receptors can be: Membrane-bound proteins on cell surfaces Intracellular enzymes Nuclear receptors affecting gene expression Ion channels regulating cellular electricity When drugs and receptors combine, they form drug-receptor complexes that trigger biological reactions. The strength of these reactions is proportional to the number of drug-receptor complexes formed—a fundamental concept in dose-response relationships. Proteins in our body exist in various forms and perform countless functions. Each protein type is specific to particular cell types. For instance, liver cell receptors differ significantly from heart cell receptors. This specificity explains why certain medications target specific organs or systems. Drugs can produce two critical effects when bound to receptors: Agonists: Drugs that activate receptors and produce a cellular response Antagonists: Drugs that block receptors and prevent normal cellular responses The Dose-Response Relationship: A Critical Concept Understanding the dose-response curve ranks among the most important concepts in pharmacology. This relationship describes how a drug’s effect correlates with the amount administered. Dose-response curves

Pharmacology is the study of how  medicinal substances interact with living systems. Pharmacology is The study of drugs, their nature, their sources,and their properties,absorption,distribution,biotransformation,elimination,interactions,toxicology and their therapeutic applications. Pharmacology is the study of the body’s reaction to drugs.or Pharmacology is study of Pharmacokinetics and Pharmacodynamics of a drug. Its Very Difficult To Summarize the whole Pharmacology but We have collected some very important Points from Various Pharmacology Books and other resources Which will Help Students Pass their exams. Important Pharmacology Points 1-10 1. Amphotericin is active against most fungi and yeasts. It can be used for intestinal candidiasis. 2. Atenolol is a beta-adrenoceptor blocker that, when administered during pregnancy, may cause intrauterine growth restriction, neonatal hypoglycaemia and bradycardia. 3. Trigger factors for migraine include intake of specific food such as caffeine,chocolate, cheese and alcoholic drinks, exposure to light, hunger and missed meals, and air travel. 4. Nalidixic acid is a quinolone that is indicated only for urinary tract infections. 5. Both levofloxacin and ciprofloxacin are quinolones. Levofloxacin has greater activity against pneumococci than ciprofloxacin. 6. Levofloxacin, which is a quinolone that has activity against Gram-positive and Gram-negative organisms including pneumococci.Quinolones are bactericidal. 7. Terazosin is a selective alpha-blocker that relaxes smooth muscle and is indicated in benign prostatic hyperplasia because it increases urinary flow rate and improves obstructive symptoms. Terazosin is also indicated in the manage-ment of mild-to-moderate hypertension. After the first dose a rapid reduction in blood pressure may occur. 8. Norfloxacin is a quinolone antibacterial agent. Quinolones should be used with caution in patients with a history of epilepsy because they may cause confusion, hallucinations and convulsions as side-effects. They may precipitate convulsions in patients with epilepsy and in those with no previous history of convulsions. 9. Tinnitus is an adverse effect of furosemide, especially when it is administered in large parenteral doses, as a rapid administration and in renal impairment.Not all diuretics are associated with tinnitus. 10. Propranolol is a beta-adrenoceptor blocking agent. The antagonist effect is associated with up-regulation of receptors. Once the drug is withdrawn abruptly, adverse reactions may occur due to the up-regulation of the receptors. Important Pharmacology Points 11-20 11. Pseudoephedrine and ephedrine are sympathomimetic agents that stimulate alpha- and beta-adrenergic receptors in the sympathetic nervous system, causing constriction of smooth muscles and blood vessels and producing bronchodilatation. They have central nervous system stimulant activity. 12. Miconazole is an imidazole antifungal that is available as an oral gel. The gel is to some extent absorbed from the oral mucosa and, because animal studies have shown that miconazole is fetotoxic, miconazole oral gel should be avoided during pregnancy. 13. Imipramine is a tricyclic antidepressant that, when administered during the third trimester, may cause tachycardia, irritability and muscle spasms in the neonate. 14. Hyoscine is an antimuscarinic agent that can be used for prophylaxis of motion sickness. Because it has a rapid onset of action it is administered 30 minutes before travelling. Cinnarizine is an antihistamine that is used for the prophylaxis of motion sickness but it has to be administered 2 h before travelling.Cetirizine is a non-sedating antihistamine that is used for symptomatic relief of allergies. 15. Chlorpromazine is an antipsychotic drug, specifically a phenothiazine derivative, that is characterised by pronounced sedative effects. Cautionary labels recommended are to avoid exposure of skin to direct sunlight or sun lamps and a warning that it may cause drowsiness and, if affected, not to drive or operate machinery and to avoid alcoholic drinks. 16. Ceftazidime is a ‘third-generation’ cephalosporin antibacterial agent. It has greater activity than cefuroxime against certain Gram-negative bacteria and less activity against Gram-positive bacteria. Ceftazidime is administered by deep intramuscular injection or intravenous injection or infusion. It is not available as tablets. 17. Salmeterol is a long-acting beta2 agonist that can be used regularly in patients with mild or moderate asthma. It can be used in combination with corticosteroid therapy. However, it should not be used in acute asthma attacks. 18. Remifentanil is a short-acting and potent opioid drug, which is preferred for use by injection for intra-operative analgesia compared with pethidine and morphine because it acts within 1–2 minutes. Its short duration of action allows prolonged administration at high dosage without accumulation and with little risk of residual respiratory depression. 19. Griseofulvin and rifampicin are enzyme inducers. They can increase the rate of synthesis of cytochrome P450 enzymes, resulting in enhanced clearance of other drugs. When enzyme inducers are administered to patients receiving warfarin, a decreased effect of warfarin results. However, warfarin itself is not known to be an enzyme inducer. 20. Finasteride is an inhibitor of the enzyme 5-reductase, which is responsible for the metabolism of testosterone into the androgen dihydrotestosterone.Finasteride is used in benign prostatic hyperplasia and at a lower dose in male-pattern baldness. Important Pharmacology Points 21-30 21. Imipramine is a tricylic antidepressant and, as with all types of antidepressants, hyponatraemia may occur in older people. This is possibly due to inappropriate secretion of antidiuretic hormone. 22. Lidocaine is indicated for ventricular arrhythmias, especially after myocardial infarction, because it suppresses ventricular tachycardia and reduces the risk of ventricular fibrillation. 23. Trifluoperazine, a phenothiazine. It may cause pancytopenia, which includes agranulocytosis. Agranulocytosis is a condition resulting in a marked decrease in the number of granulocytes. 24. Piroxicam, which is a non-steroidal anti-inflammatory drug that does not exhibit selectivity for cyclo-oxygenase-2 inhibition.Celecoxib, etoricoxib, meloxicam and Lumiracoxib are all selective inhibitors of cyclo-oxygenase-2. 25. Ibuprofen is a non-steroidal anti-inflammatory drug which brings about a reduction in the formation of prostaglandins that occur in an inflammatory reaction. Ibuprofen achieves this action by reversibly inhibiting cyclooxygenase enzymes. It is a propionic acid derivative. 26. Zanamivir is an antiviral agent used in influenza because it reduces replication of influenza A and B viruses by inhibiting the viral enzyme neuraminidase.It normally reduces the duration of symptoms by around 1–1.5 days.Zanamivir is not licensed for prophylaxis of influenza. It is indicated for the treatment of influenza and should be started within 48 h of the first symptoms.It is

Q 1. As An Antiepileptic drug, Phenytoin is most similar in action to which one of the following drugs? (A)Digoxin (B)Propafenone (C)Lidocaine (D)Sotalol (E)Verapamil Answer: C (Lidocaine) Explanations: Phenytoin and lidocaine are Both similar in action both are class IB Antiarrhythmic agents.These drugs slightly depress phase 0 and may shorten the duration of the action potential.They are most commonly used for the treatment of ventricular arrhythmia. Q2.How does Clonidine, An Antihypertensive drug, Work? (A)Block Alpha 1 Adrenergic Receptors (B)Stimulate Alpha 2 Adrenergic Receptors In The Brain. (C)Increase heart rate due to stimulation of SA Node (D)Block Beta Adrenoceptors. Answer: B (Stimulate alpha 2 adrenergic receptors in the brain) Explanation: Clonidine stimulates the alpha 2 adrenergic receptors in the vasomotor center of the brain, leading to decrease in activity of sympathetic nerves to the peripheral tissues.Inhibition of the sympathetic nerves to the heart will lead to decrease in the cardiac output, and inhibition of the sympathetic nerves to the blood vessels will cause vasodilation.both of these effects will cause fall in the blood pressure. Q.3 Phentolamine is a (an) (A)Alpha 1 adrenergic antagonist (B)Beta 2 adrenergic antagonist (C)Both alpha 1+2  Antagonist (D)Mainly Alpha 2 adrenergic antagonist. Answer: C (Both alpha 1+2 Antagonist Explanation: Phentolamine blocks both alpha 1 and alpha 2 receptors equally.Phentolamine blocks the alpha receptors for a short period of time and its blocking effect on the alpha receptors is reversible. Note: We Will Upload More Such Questions, Keep Visiting DrugsBank

Pharmacology is one of the most important subject in the Pharmacy profession as well as in medical field. Pharmacology is the corner stone of the modern pharmacy. Here is a list of important General Pharmacology Questions which every pharmacy and medical students should know. Top 20 General Pharmacology Questions Q.1  What is Pharmacology? Ans: Pharmacology is a branch of science that deals with the interaction of drugs with living organisms. Or The study of Pharmacokinetics and Pharmacodynamics. Q.2 What is a Drug? Ans: A drug is any chemical entity that causes a change in biological function in a living organism.some drugs are formed inside the body such as insulin and noradrenaline etc.drugs that are introduced into the body from outside are called Xenobiotics. Q.3 What Is a Dose? Ans: A Specific Amount of Drug Prescribed to be taken at one time. Q.4 What Is Blood Brain Barrier? It is A Tight Endothelial Cells Of the Brain Capillaries And Glial Cells Of The Brain Around The blood capillaries that doesn’t allow the passage of certain lipid insoluble substances to pass from the blood into the brain.Lipid Soluble Drugs can easily Cross This Barrier.Examples Of Lipid soluble Drugs are; Diazepam, Thiopental, And Phenobarbitol. Q.5 What is Volume Of Distribution? Ans: The total Volume Of The Body Fluid in which a drug appears to be distributed according to its concentration in the blood or plasma.VD of a drug can be determined by the following Formula, VD (Volume OF Distribution) =Total Amount OF Drug In the Body/Concentration of drug in the blood plasma. Q.6 What Is Potency? Ans: It is the weight of the drug that produces a certain magnitude of response.For Example Lesser the weight of drug required to produce a given effect, more its potency.Also More the weight of the drug required to produce the same effect lesser its potency.e.g Clonidine Produce its antihypertensive effect in 0.2-0.3mg Daily Dose.While Antihypertensive dose of methyldopa is 500-2000mg Per Day.Thus Clonidine IS more Potent than methyldopa. Q.7 What Is Efficacy? Ans:If the dose of a drug is increased its effect will be increased proportionately, until a stage is reached beyond there is no further increase in effect will occur,even if a large dose of drug is given.thix maximum effect of drug beyond which no further increase in its effect occurs even if the dose of the drug is increased to a large amount is called efficacy or maximal efficacy.example morphine has more efficacy than aspirin as an analgesic .morphine is more effective in the severe type of pains while aspirin is effective in mild to moderate pain. Q.8 What is Therapeutic index? The ratio between median toxic dose (TD50) and median effective dose (ED50) is called therapeutic index. Therapeutic index= TD50/ED50 Q.9 What is idiosyncrasy? It is a rare type of response to a drug that is not related to its dose, that is, even a small dose can cause it.For example.A rare adverse effect with chloramphenicol is aplastic anemia. Q.10 What is Hypersensitivity? An allergic or immunological response to a drug .for example anaphylactic shock with penicillin is a severe type of hypersensitivity reaction. Q.11 What is Tolerance? Ans: Repeated use of a drug causes a gradual decrease in the response to the drug.e.g chronic use of morphine will decrease many of its effects in the body, therefore the dose of the drug has to be increased with the passage of time to maintain the usual effects of the drug. Q.12 What is a Receptor? Ans: Receptor is a macromolecule (Big molecule).Most of the receptors are protein in nature.mostly those drugs that act on the cells bind to the receptors.Those drugs which bind to the receptor and show their effect are called agonists.While some drugs bind to the receptor but don’t produce an effect.These drugs are known as an antagonist as they prevent the binding of agonists with the receptors. Q.14 What is the adverse drug reaction? Drugs may produce two types of effect i.e Useful effects and harmful effects.harmful effects are also known as adverse drug reaction or undesired effects.These effects may range from the mild type of adverse effect to severe effects that may cause a death of the person. Adverse drug reaction may be classified into the following types; Idiosyncrasy Drug allergy Direct toxic effect Drug dependence Tolerance Q.15 What is Shock? It is a clinical condition in which there is an inadequate supply of blood to tissues.it causes hypotension, oliguria, and metabolic acidosis.Following are the common types of shock: A. Hypovolemic shock B. Septic shock C. Cardiogenic shock D. Anaphylactic shock Q.16 What is Drug Clearance? Ans: It Can be defined as Volume Of blood or plasma cleared of the drug in a unit period of time.Thus, to determine clearance we have to find that volume of blood or plasma from which a drug is removed during a unit period of time.By removal of drug we mean metabolism and excretion of drug.if we know the clearance of a drug we can adjust its dose properly.clearance of the drug can be determined by the following formula. Cl: Rate of elimination/Concentration of drug in the blood Where is Cl is clearance? Q.17 What is Drug Excretion? Ans: Removal of drugs from the body is known as their excretion.Drugs are excreted from the body either in the form of their metabolites or in unchanged form.Excretion can occur from the following routes; A) Faecal B) Renal C) Biliary D)Pulmonary E)Others like to sweat, saliva, milk etc Q.18 What is Toxicology? It is an aspect of pharmacology that deals with the adverse effects of drugs on living organisms .in addition to drugs used in therapy, it also deals with many other chemicals that may be responsible for the household, environmental, or industrial intoxication. Q.19 What is antidote? Ans: Antidotes are Any Substance which Is Used To oppose the effects of poisons without causing any damage to The body. Example antidote for benzodiazepine is flumazenil. Q.20 What is Bioavailability? It can be defined as a fraction of unmodified drug