Questions and Answers
Which of the following diuretics acts on the site shown in the figure?
Hydrochlorothiazide works by inhibiting which pump?
At a high altitude of 3000m, a person complains of breathlessness. All of the following can be used for the management of this person except:
What is the aim of treatment in Acute Congestive Heart Failure (CHF)?
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Which drug class can be used as inotropics in CHF?
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The mechanism of action of nitrates involves the release of ______.
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Xanthopsia is the most common adverse effect of digoxin.
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Which of the following is a drug that can cause gynaecomastia?
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Study Notes
Here are the study notes for the provided text:
Chapter 1: General Pharmacology
- Pharmacology is the science dealing with drugs.
- There are two branches:
- PharmacoKinetics (PK): Effect of Body on Drug
- PharmacoDynamics (PD): Effect of Drug on Body
PharmacoKinetics (PK)
- Aka ADME Study
- Includes:
- Absorption (A)
- Distribution (D)
- Metabolism (M)
- Excretion (E)
- Bioavailability: Fraction of given dose that reaches the systemic circulation in unchanged form
- IV route: Bioavailability = 100%
- First Pass metabolism/pre-systemic metabolism: Decreases bioavailability
Absorption (A)
- Lipid Solubility is the most important factor in absorption
- When the medium is the same, then the drug will cross:
- Acidic drugs in acidic medium: Non-ionized, Lipid soluble, and crosses easily
- Basic drugs in basic medium: Non-ionized, Lipid soluble, and crosses easily
- Acidic drugs in basic medium: Ionized, Water soluble, and does not cross
- Basic drugs in acidic medium: Ionized, Water soluble, and does not cross
- Cmax: Maximum concentration obtained by a particular dose
- Tmax: Time in which plasma concentration becomes maximum
- AUC: Total area covered by the graph, tells extent of absorption
Distribution (D)
- Measure of amount of drug in tissues after absorption in the systemic circulation
- Depends on lipid solubility and plasma protein binding
- Acidic drugs bind to Albumin, Basic drugs bind to α1 Acid Glycoprotein
- High PPB drugs have:
- Low Vd (Volume of Distribution)
- Long duration of action
- More drug interactions
- Loading Dose (LD): Initial high dose given to start the action
- Maintenance Dose (MD): Repeated doses given to maintain the plasma concentration
Metabolism (M)
- Aim: To make a drug water soluble (polar)
- Phase I Reactions: Mostly catabolic, includes Oxidation, Reduction, Hydrolysis, Cyclization, and Deamination
- Phase II Reactions: Mostly anabolic, includes Glucuronidation, Glutathione conjugation, Acetylation, Methylation, and Sulfate conjugation
- Purpose of Phase I: Expose the functional group on the drug
- Purpose of Phase II: Makes the drug water soluble
- Enzymes: Divided into Microsomal and Non-microsomal; Microsomal enzymes can be induced or inhibited
Excretion (E)
- Glomerular Filtration: Lipid soluble and water soluble drugs can be filtered
- Tubular Reabsorption: Lipid soluble drugs are reabsorbed, water soluble drugs are excreted
- Tubular Secretion: Due to pumps/transporters in proximal tubules; Lipid soluble drugs are secreted
- Half-life (t1/2): Time in which plasma concentration of a drug becomes half
- Clinical importance of t1/2: Dose cannot be calculated, dosing interval/frequency can be known
PharmacoDynamics (PD)
- Deals with the action of a drug as well as the mechanism of action
- Mechanisms of action:
- Enzyme inhibition
- Receptors (Ionotropic, Enzymatic, and G-protein coupled receptors)
Receptors
- Ionotropic Receptors: Present on ion channels, also known as ligand-gated channels
- Enzymatic Receptors: Present on cell membrane with intracellular and extracellular ends (e.g., Tyrosine Kinase Receptors)
- G-protein Coupled Receptors (GPCRs): Works by one out of the three mechanisms ( changing cAMP level, Ca2+ level, or opening ion channels)
- Inracellular Receptors: Only lipid soluble drugs act through these receptors, which are of two types (Cytoplasmic and Nuclear Receptors)
Log Dose Response Curve (Log DRC)
- S-shaped curve (Sigmoid Curve)
- Clinically more useful than DRC
- Three important parameters obtained from log DRC:
- Potency
- Efficacy
- Slope
Quantal Dose Response Curve (Quantal DRC)
- For All or None phenomenon, where grade of response cannot be plotted
- Percentage of subjects responding are kept on Y-axis
- Tells about effect of a drug in population
- ED50 (Median Effective dose): 50% respond to a particular dose
- LD50 (Median Lethal dose): 50% of animals die after receiving a particular dose
- Therapeutic index (TI) = LD50/ED50Here are the study notes based on the provided text:
Autonomic Nervous System
-
Origin:
- Preganglionic parasympathetic and sympathetic neurons release ACh as the neurotransmitter
- Postganglionic parasympathetic neurons release ACh, while postganglionic sympathetic neurons release NA
-
Actions:
- Heart: Parasympathetic stimulation decreases heart rate (↓), while sympathetic stimulation increases heart rate (↑)
- Bronchus: Parasympathetic stimulation causes bronchoconstriction, while sympathetic stimulation causes bronchodilation
- GIT: Parasympathetic stimulation increases peristalsis, while sympathetic stimulation decreases peristalsis
- Bladder: Parasympathetic stimulation contracts bladder muscles, while sympathetic stimulation relaxes bladder muscles
- Pupil: Parasympathetic stimulation causes miosis, while sympathetic stimulation causes mydriasis
- Sexual system: Parasympathetic stimulation causes erection, while sympathetic stimulation causes ejaculation
Cholinergic Drugs
-
Directly Acting Cholinergic Drugs:
- Stimulate parasympathetic system
- Examples: Pilocarpine, Bethanechol, Carbachol
-
Indirectly Acting Cholinergic Drugs:
- Act by inhibiting AChE
- Examples: Physostigmine, Neostigmine, Pyridostigmine
- Reversible AChE Inhibitors: Used clinically, e.g., Neostigmine
- Irreversible AChE Inhibitors: Toxic, e.g., Organophosphates
Anticholinergic Drugs
-
Organ:
- Stomach: Blocks M1 receptors, relieving peptic ulcer symptoms
- Heart: Blocks M2 receptors, increasing heart rate
- Bronchus: Blocks M3 receptors, relieving bronchial asthma
- Bladder: Blocks M3 receptors, relieving overactive bladder
- Eye: Blocks M3 receptors, relieving mydriasis
-
Uses:
- Peptic ulcer
- Bradycardia
- Bronchial asthma
- Overactive bladder
- Refraction testing
- Iridocyclitis
Sympathetic Nervous System
- Major neurotransmitter: Noradrenaline (NA)
-
Adrenergic Receptors:
- α1: Vasoconstriction
- α2: Presynaptic receptor, acting as a brake on sympathetic system
- β1: Increase heart rate and contractility
- β2: Relax smooth muscles, causing bronchodilation and vasodilation
- β3: Lipolysis
Adrenergic Drugs
-
Directly Acting Adrenergic Drugs:
- Stimulate adrenergic receptors
- Examples: Adrenaline, Noradrenaline, Isoprenaline
-
Indirectly Acting Adrenergic Drugs:
- Act by releasing NA from nerve terminals
- Examples: Ephedrine, Amphetamine
- α1 Blockers: Used in hypertension, e.g., Prazosin
- β Blockers: Used in hypertension, angina, and cardiac arrhythmias, e.g., Propranolol
Glaucoma
- Characteristics: Increased intraocular pressure (IOP) due to increased aqueous humor production or decreased drainage
-
Treatment:
- β Blockers: Decrease aqueous humor production
- Prostaglandin analogues: Increase aqueous humor drainage
- α2 Agonists: Decrease aqueous humor production and increase drainage
- Carbonic anhydrase inhibitors: Decrease aqueous humor production
Previous Years Questions
- Q1: Muscarinic receptor stimulation leads to erection, increased contraction of cardiac muscles, and bronchodilation.
- Q2: Pinpoint pupils and increased secretions are symptoms of organophosphate poisoning.
- Q3: Topical antiglaucoma drug dorzolamide acts by carbonic anhydrase inhibition.
- Q4: The next line of management for the patient with snake bite symptoms would be to administer atropine and neostigmine.
- Q5: Edrophonium is used to differentiate myasthenia gravis from cholinergic crisis.
- Q6: The patient's symptoms are consistent with cholinergic crisis.
- Q7: The graph shows the effect of ACh on isolated mammalian intestinal tissue.
- Q8: The experiment demonstrates the effect of adrenaline on dog blood pressure.
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Description
Quick revision notes on general pharmacology, covering pharmacokinetics, pharmacodynamics, absorption, bioavailability, and first pass metabolism.