This document discusses pharmacokinetics and biotransformation. It covers the four main stages of pharmacokinetics: absorption, distribution, metabolism, and excretion. Metabolism, or biotransformation, involves enzymatic conversion of drugs by the liver and involves two phases - phase I and phase II reactions. Phase I introduces or exposes functional groups using oxidation, reduction or hydrolysis. Phase II involves conjugation reactions like glucuronidation and sulfation. Cytochrome P450 enzymes and microsomal enzymes are responsible for many phase I reactions. Factors like enzyme induction and inhibition can impact drug metabolism and clearance from the body.
Metabolic Changes of Drugs and Related Organic Compounds describes the human metabolic processes of various functional groups found in therapeutic agents.
The importance of a chapter on metabolism lies in the fact that drug interactions are based on these processes.
For pharmacists, it is necessary for them to understand why certain drugs are contraindicated with other drugs.
This chapter attempts to describe the various phases of drug metabolism, the sites where these biotransformation will occur, the role of specific enzymes, metabolism of specific functional groups, and several examples of the metabolism of currently used therapeutic agents.
Metabolic Changes of Drugs and Related Organic Compounds describes the human metabolic processes of various functional groups found in therapeutic agents.
The importance of a chapter on metabolism lies in the fact that drug interactions are based on these processes.
For pharmacists, it is necessary for them to understand why certain drugs are contraindicated with other drugs.
This chapter attempts to describe the various phases of drug metabolism, the sites where these biotransformation will occur, the role of specific enzymes, metabolism of specific functional groups, and several examples of the metabolism of currently used therapeutic agents.
DRUG INTERACTIONS (MECHANISMS OF DRUG-DRUG INTERACTIONS)N Anusha
A Drug interaction is an interaction between a drug and some other substance, such as another drug or a certain type of food, which leads to interaction that could manifest as an increase or decrease in the effectiveness or an adverse reaction or a totally new side effect that is not seen with either drug alone that can be severe enough to alter the clinical outcome.
Every time a drug is administered with any other prescription medicine, OTC products, herbs or even food we expose ourselves to the risk of a potentially dangerous interaction.
Phase I Vs Phase II Drug metabolism and factors affectiing drug metabolism.
Enzyme induction, Enzyme inhibitor, physicochemical properties wthich acan affect the drug metabolism
metabolism of xenobiotis, drugs, medicine, carcinogen generation by enzymes like cyt p450 mono oxigenases, prostaglandin synthase ect. alcohol metabolism, toxin metabolism, definition of genobiotics, biotransformation, detoxification. effects on health
biotransformation of drug
Biotransformation/Xenobiotic metabolism/ drug metabolism/detoxification.
-Xenobiotics: a wide variety of foreign compounds to which humans get exposed in day to day life.
-It includes unknown compounds, drugs, environmental pollutants, toxins.
-Many xenobiotics can evoke biological responses.
DEFINITION
The biochemical alteration of drug or xenobiotic in the presence of various enzymes that acts as a catalyst which themselves not consumed in the reaction and there by may activate or deactivate the drug is called biotransformation.
Why Biotransformation is necessary?:
To easily eliminate the drug
To terminate drug action by inactivating it
Consequences of Biotransformation
Active to Inactive:
Phenobarbitone---- Hydroxyphenobarbitone
Inactive (prodrug) to Active :
L-Dopa ---- Dopamine
Parathion -- Paraoxon
Talampicillin -- Ampicillin
Active to equally active:
Diazepam -- Oxazepam
Amitriptyline -- Nortriptyline
Imipramine -- Des-imipramine
Codeine -- Morphine
Sites of biotransformation
In the body: Liver, small and large intestines, lungs, skin, kidney, nasal mucosa & brain.
Liver is considered “metabolite clearing house” for both endogenous substances and xenobiotics.
Intestines are considered “initial site of drug metabolism”.
FIRST PASS METABOLISM:
First pass metabolism or presystemic
metabolism or ‘first pass effect’
After oral administeration many drugs are absorbed from the small intestine - transported first via portal system to the liver, where they undergo extensive metabolism before reaching systemic circulation.
fundamental concepts in drug biotransformation
Lipid soluble drugs are poorly excreted in the urine. They tend to store in fat and/or circulate until they are converted (phase I biotransformation) to more water soluble metabolites or metabolites that conjugate (phase II biotransformation) with water soluble substances.
Water soluble drugs are more readily excreted in the urine. They may be metabolized, but generally not by the CYP enzyme systems.
Enzymes catalyzing phase I biotransformation reactions
Enzymes catalyzing phase I biotransformation reactions include:
cytochrome P-450
aldehyde and alcohol dehydrogenase
deaminases
esterases
amidases
epoxide hydratases
Addition of water
Cleavage of R-O or R-N bond accompanied by addition of H2O
CYTOCHROME P450
The cytochrome P-450 families are referred to using an arabic numeral, e.g., CYP1, CYP2, etc.
Each family has a number of subfamilies denoted by an upper case letter, e.g., CYP2A, CYP2B, etc.
The individual enzymes within each subfamily are denoted by another arabic numeral, e.g., CYP3A1, CYP3A2, etc.
DRUG INTERACTIONS (MECHANISMS OF DRUG-DRUG INTERACTIONS)N Anusha
A Drug interaction is an interaction between a drug and some other substance, such as another drug or a certain type of food, which leads to interaction that could manifest as an increase or decrease in the effectiveness or an adverse reaction or a totally new side effect that is not seen with either drug alone that can be severe enough to alter the clinical outcome.
Every time a drug is administered with any other prescription medicine, OTC products, herbs or even food we expose ourselves to the risk of a potentially dangerous interaction.
Phase I Vs Phase II Drug metabolism and factors affectiing drug metabolism.
Enzyme induction, Enzyme inhibitor, physicochemical properties wthich acan affect the drug metabolism
metabolism of xenobiotis, drugs, medicine, carcinogen generation by enzymes like cyt p450 mono oxigenases, prostaglandin synthase ect. alcohol metabolism, toxin metabolism, definition of genobiotics, biotransformation, detoxification. effects on health
biotransformation of drug
Biotransformation/Xenobiotic metabolism/ drug metabolism/detoxification.
-Xenobiotics: a wide variety of foreign compounds to which humans get exposed in day to day life.
-It includes unknown compounds, drugs, environmental pollutants, toxins.
-Many xenobiotics can evoke biological responses.
DEFINITION
The biochemical alteration of drug or xenobiotic in the presence of various enzymes that acts as a catalyst which themselves not consumed in the reaction and there by may activate or deactivate the drug is called biotransformation.
Why Biotransformation is necessary?:
To easily eliminate the drug
To terminate drug action by inactivating it
Consequences of Biotransformation
Active to Inactive:
Phenobarbitone---- Hydroxyphenobarbitone
Inactive (prodrug) to Active :
L-Dopa ---- Dopamine
Parathion -- Paraoxon
Talampicillin -- Ampicillin
Active to equally active:
Diazepam -- Oxazepam
Amitriptyline -- Nortriptyline
Imipramine -- Des-imipramine
Codeine -- Morphine
Sites of biotransformation
In the body: Liver, small and large intestines, lungs, skin, kidney, nasal mucosa & brain.
Liver is considered “metabolite clearing house” for both endogenous substances and xenobiotics.
Intestines are considered “initial site of drug metabolism”.
FIRST PASS METABOLISM:
First pass metabolism or presystemic
metabolism or ‘first pass effect’
After oral administeration many drugs are absorbed from the small intestine - transported first via portal system to the liver, where they undergo extensive metabolism before reaching systemic circulation.
fundamental concepts in drug biotransformation
Lipid soluble drugs are poorly excreted in the urine. They tend to store in fat and/or circulate until they are converted (phase I biotransformation) to more water soluble metabolites or metabolites that conjugate (phase II biotransformation) with water soluble substances.
Water soluble drugs are more readily excreted in the urine. They may be metabolized, but generally not by the CYP enzyme systems.
Enzymes catalyzing phase I biotransformation reactions
Enzymes catalyzing phase I biotransformation reactions include:
cytochrome P-450
aldehyde and alcohol dehydrogenase
deaminases
esterases
amidases
epoxide hydratases
Addition of water
Cleavage of R-O or R-N bond accompanied by addition of H2O
CYTOCHROME P450
The cytochrome P-450 families are referred to using an arabic numeral, e.g., CYP1, CYP2, etc.
Each family has a number of subfamilies denoted by an upper case letter, e.g., CYP2A, CYP2B, etc.
The individual enzymes within each subfamily are denoted by another arabic numeral, e.g., CYP3A1, CYP3A2, etc.
Clinical pharmacokinetic studies are performed to examine the absorption, distribution, metabolism, and excretion of a drug under investigation in healthy volunteers and/or patients
It will provide you a complete journey through the routes of drug administration, with all the basics covered I hope this presentation will make your fundamentals crystal clear.
New Directions in Targeted Therapeutic Approaches for Older Adults With Mantl...i3 Health
i3 Health is pleased to make the speaker slides from this activity available for use as a non-accredited self-study or teaching resource.
This slide deck presented by Dr. Kami Maddocks, Professor-Clinical in the Division of Hematology and
Associate Division Director for Ambulatory Operations
The Ohio State University Comprehensive Cancer Center, will provide insight into new directions in targeted therapeutic approaches for older adults with mantle cell lymphoma.
STATEMENT OF NEED
Mantle cell lymphoma (MCL) is a rare, aggressive B-cell non-Hodgkin lymphoma (NHL) accounting for 5% to 7% of all lymphomas. Its prognosis ranges from indolent disease that does not require treatment for years to very aggressive disease, which is associated with poor survival (Silkenstedt et al, 2021). Typically, MCL is diagnosed at advanced stage and in older patients who cannot tolerate intensive therapy (NCCN, 2022). Although recent advances have slightly increased remission rates, recurrence and relapse remain very common, leading to a median overall survival between 3 and 6 years (LLS, 2021). Though there are several effective options, progress is still needed towards establishing an accepted frontline approach for MCL (Castellino et al, 2022). Treatment selection and management of MCL are complicated by the heterogeneity of prognosis, advanced age and comorbidities of patients, and lack of an established standard approach for treatment, making it vital that clinicians be familiar with the latest research and advances in this area. In this activity chaired by Michael Wang, MD, Professor in the Department of Lymphoma & Myeloma at MD Anderson Cancer Center, expert faculty will discuss prognostic factors informing treatment, the promising results of recent trials in new therapeutic approaches, and the implications of treatment resistance in therapeutic selection for MCL.
Target Audience
Hematology/oncology fellows, attending faculty, and other health care professionals involved in the treatment of patients with mantle cell lymphoma (MCL).
Learning Objectives
1.) Identify clinical and biological prognostic factors that can guide treatment decision making for older adults with MCL
2.) Evaluate emerging data on targeted therapeutic approaches for treatment-naive and relapsed/refractory MCL and their applicability to older adults
3.) Assess mechanisms of resistance to targeted therapies for MCL and their implications for treatment selection
The prostate is an exocrine gland of the male mammalian reproductive system
It is a walnut-sized gland that forms part of the male reproductive system and is located in front of the rectum and just below the urinary bladder
Function is to store and secrete a clear, slightly alkaline fluid that constitutes 10-30% of the volume of the seminal fluid that along with the spermatozoa, constitutes semen
A healthy human prostate measures (4cm-vertical, by 3cm-horizontal, 2cm ant-post ).
It surrounds the urethra just below the urinary bladder. It has anterior, median, posterior and two lateral lobes
It’s work is regulated by androgens which are responsible for male sex characteristics
Generalised disease of the prostate due to hormonal derangement which leads to non malignant enlargement of the gland (increase in the number of epithelial cells and stromal tissue)to cause compression of the urethra leading to symptoms (LUTS
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Anti ulcer drugs and their Advance pharmacology ||
Anti-ulcer drugs are medications used to prevent and treat ulcers in the stomach and upper part of the small intestine (duodenal ulcers). These ulcers are often caused by an imbalance between stomach acid and the mucosal lining, which protects the stomach lining.
||Scope: Overview of various classes of anti-ulcer drugs, their mechanisms of action, indications, side effects, and clinical considerations.
Flu Vaccine Alert in Bangalore Karnatakaaddon Scans
As flu season approaches, health officials in Bangalore, Karnataka, are urging residents to get their flu vaccinations. The seasonal flu, while common, can lead to severe health complications, particularly for vulnerable populations such as young children, the elderly, and those with underlying health conditions.
Dr. Vidisha Kumari, a leading epidemiologist in Bangalore, emphasizes the importance of getting vaccinated. "The flu vaccine is our best defense against the influenza virus. It not only protects individuals but also helps prevent the spread of the virus in our communities," he says.
This year, the flu season is expected to coincide with a potential increase in other respiratory illnesses. The Karnataka Health Department has launched an awareness campaign highlighting the significance of flu vaccinations. They have set up multiple vaccination centers across Bangalore, making it convenient for residents to receive their shots.
To encourage widespread vaccination, the government is also collaborating with local schools, workplaces, and community centers to facilitate vaccination drives. Special attention is being given to ensuring that the vaccine is accessible to all, including marginalized communities who may have limited access to healthcare.
Residents are reminded that the flu vaccine is safe and effective. Common side effects are mild and may include soreness at the injection site, mild fever, or muscle aches. These side effects are generally short-lived and far less severe than the flu itself.
Healthcare providers are also stressing the importance of continuing COVID-19 precautions. Wearing masks, practicing good hand hygiene, and maintaining social distancing are still crucial, especially in crowded places.
Protect yourself and your loved ones by getting vaccinated. Together, we can help keep Bangalore healthy and safe this flu season. For more information on vaccination centers and schedules, residents can visit the Karnataka Health Department’s official website or follow their social media pages.
Stay informed, stay safe, and get your flu shot today!
ARTIFICIAL INTELLIGENCE IN HEALTHCARE.pdfAnujkumaranit
Artificial intelligence (AI) refers to the simulation of human intelligence processes by machines, especially computer systems. It encompasses tasks such as learning, reasoning, problem-solving, perception, and language understanding. AI technologies are revolutionizing various fields, from healthcare to finance, by enabling machines to perform tasks that typically require human intelligence.
Title: Sense of Taste
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
Prix Galien International 2024 Forum ProgramLevi Shapiro
June 20, 2024, Prix Galien International and Jerusalem Ethics Forum in ROME. Detailed agenda including panels:
- ADVANCES IN CARDIOLOGY: A NEW PARADIGM IS COMING
- WOMEN’S HEALTH: FERTILITY PRESERVATION
- WHAT’S NEW IN THE TREATMENT OF INFECTIOUS,
ONCOLOGICAL AND INFLAMMATORY SKIN DISEASES?
- ARTIFICIAL INTELLIGENCE AND ETHICS
- GENE THERAPY
- BEYOND BORDERS: GLOBAL INITIATIVES FOR DEMOCRATIZING LIFE SCIENCE TECHNOLOGIES AND PROMOTING ACCESS TO HEALTHCARE
- ETHICAL CHALLENGES IN LIFE SCIENCES
- Prix Galien International Awards Ceremony
Title: Sense of Smell
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the primary categories of smells and the concept of odor blindness.
Explain the structure and location of the olfactory membrane and mucosa, including the types and roles of cells involved in olfaction.
Describe the pathway and mechanisms of olfactory signal transmission from the olfactory receptors to the brain.
Illustrate the biochemical cascade triggered by odorant binding to olfactory receptors, including the role of G-proteins and second messengers in generating an action potential.
Identify different types of olfactory disorders such as anosmia, hyposmia, hyperosmia, and dysosmia, including their potential causes.
Key Topics:
Olfactory Genes:
3% of the human genome accounts for olfactory genes.
400 genes for odorant receptors.
Olfactory Membrane:
Located in the superior part of the nasal cavity.
Medially: Folds downward along the superior septum.
Laterally: Folds over the superior turbinate and upper surface of the middle turbinate.
Total surface area: 5-10 square centimeters.
Olfactory Mucosa:
Olfactory Cells: Bipolar nerve cells derived from the CNS (100 million), with 4-25 olfactory cilia per cell.
Sustentacular Cells: Produce mucus and maintain ionic and molecular environment.
Basal Cells: Replace worn-out olfactory cells with an average lifespan of 1-2 months.
Bowman’s Gland: Secretes mucus.
Stimulation of Olfactory Cells:
Odorant dissolves in mucus and attaches to receptors on olfactory cilia.
Involves a cascade effect through G-proteins and second messengers, leading to depolarization and action potential generation in the olfactory nerve.
Quality of a Good Odorant:
Small (3-20 Carbon atoms), volatile, water-soluble, and lipid-soluble.
Facilitated by odorant-binding proteins in mucus.
Membrane Potential and Action Potential:
Resting membrane potential: -55mV.
Action potential frequency in the olfactory nerve increases with odorant strength.
Adaptation Towards the Sense of Smell:
Rapid adaptation within the first second, with further slow adaptation.
Psychological adaptation greater than receptor adaptation, involving feedback inhibition from the central nervous system.
Primary Sensations of Smell:
Camphoraceous, Musky, Floral, Pepperminty, Ethereal, Pungent, Putrid.
Odor Detection Threshold:
Examples: Hydrogen sulfide (0.0005 ppm), Methyl-mercaptan (0.002 ppm).
Some toxic substances are odorless at lethal concentrations.
Characteristics of Smell:
Odor blindness for single substances due to lack of appropriate receptor protein.
Behavioral and emotional influences of smell.
Transmission of Olfactory Signals:
From olfactory cells to glomeruli in the olfactory bulb, involving lateral inhibition.
Primitive, less old, and new olfactory systems with different path
These simplified slides by Dr. Sidra Arshad present an overview of the non-respiratory functions of the respiratory tract.
Learning objectives:
1. Enlist the non-respiratory functions of the respiratory tract
2. Briefly explain how these functions are carried out
3. Discuss the significance of dead space
4. Differentiate between minute ventilation and alveolar ventilation
5. Describe the cough and sneeze reflexes
Study Resources:
1. Chapter 39, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 34, Ganong’s Review of Medical Physiology, 26th edition
3. Chapter 17, Human Physiology by Lauralee Sherwood, 9th edition
4. Non-respiratory functions of the lungs https://academic.oup.com/bjaed/article/13/3/98/278874
5. •Involves enzymic conversion of one chemical entity to
another within the body.
• Occurs between absorption of the drug into the
circulation and its elimination.
• Renders non polar (lipid soluble) compounds polar
(lipid insoluble).
• Sites- liver, GIT, lungs, kidneys, brain, skin.
6. Consequences in a biotransformation reaction:
Formation of an inactive metabolite from a
pharmacologically active drug.
Eg: 6- Mercaptopurine 6- Mercapturic acid
(Active drug) (Inactive metabolite)
Formation of an active metabolite from an inactive or a
lesser active drug.
Eg: L- dopa Dopamine in basal ganglia
(Inactive) (Active)
7. Formation of an active metabolite from an equally
active drug.
Eg: Diazepam Oxazepam
(Active) (Active metabolite)
Formation of a toxic metabolite from an active drug.
Eg: Paracetamol N- acetyl- p- benzoquinoneimine
(Active) (Toxic metabolite)
8. MICROSOMAL ENZYMES
• Drug metabolizing enzymes associated with smooth
endoplasmic reticulum of the liver.
•Principal enzymes involved:
- Mixed Function Oxidase
- Cytochrome P450
•Non specific in action.
•Can be induced, activated. Can metabolize only lipid
soluble drugs.
•Primarily concerned with phase I oxidation and
reduction.
9. The activity of MFO’s require a reducing agent
(nicotinamide adenine dinucleotide phosphate [NADPH])
and molecular oxygen.
In a typical reaction, one molecule of oxygen is
consumed (reduced) per substrate molecule, with one
oxygen atom appearing in the product and the other in
the form of water.
Drug + O2 + NADPH + H+ Drug metabolite + H2O +
NADP+
10. Cytochrome P450 abbreviated as P450 or CYP- a
haemoprotein.
Classified into families designated as 1,2,3,4 and
subfamilies by letters A, B, C, D.
Another number is added to indicate specific
isoenzyme. Eg: CYP2A6.
11.
12. These enzymes differ from one another in:
Amino acid sequence.
Sensitivity to inhibitors and inducing agents.
Specificity of the reactions they catalyse.
15. PHASE I REACTIONS
Functions to convert lipophilic molecules into polar
molecules by introducing or unmasking a polar
functional group like –OH or –NH2 .
Involves Oxidation, Reduction and Hydrolysis.
16. OXIDATION:
Microsomal oxidation causes aromatic or aliphatic
hydroxylation, deamination, dealkylation or S-oxidation.
These reactions involve reduced nicotinamide adenine
dinucleotide phosphate(NADP), molecular O2 and one
or more group of CYP450.
Drug + O2 + NADPH + H+ Drug- OH + H2O + NADP+
Can also involve other MFO’s like flavin containing
monooxygenases or epoxide hydrolases.
17.
18.
19. REDUCTION:
Reduction requires reduced NADP-cytochrome-c
reductase or reduced NAD-cytochrome b5 reductase.
HYDROLYSIS:
These reactions do not involve hepatic microsomal
enzymes.
Occur in plasma and other tissues.
Both ester and amide bonds are susceptible to
hydrolysis.
20.
21. PHASE II REACTIONS
Consists of conjugation reactions.
Drugs already possessing an –OH, -NH2 , -COOH
group may enter phase II directly without prior phase I
metabolism.
Involves acetylation, methylation, glucuronidation,
sulphation, mercaptopuric acid formation, glutathione
conjugation.
22. AMINO ACID REACTIONS:
Glycine and glutamine are chiefly involved.
Glycine forms conjugates with nicotinic acid and
salicylates.
Glutamine forms conjugates with p-aminosalicylates.
23. ACETYLATION:
Acetate derived from acetyl coA conjugates with drugs
like isoniazid, sulfonamides.
This activity resides in the cytosol and occurs in the
leucocytes, gastrointestinal epithelium and the liver.
24. GLUCURONIDATION:
Catalysed by UDP- glucuronyl tranferase enzyme.
Conjugation reactions between glucuronic acid and
carboxyl groups are involved in the metabolism of
bilirubin, diazepam etc.
26. METHYLATION:
Proceeds by a pathway involving S-adenosyl
methionine as methyl donor to drugs with free amino,
hydroxyl or thiol groups.
Eg: Catechol-O-methyl transferase.
Present in the cytosol.
27. Methylates the terminal – NH2 residue of noradrenaline
to form adrenaline in the adrenal medulla
Catalyses the transfer of a methyl group to
catecholamines, inactivating noradrenaline, dopamine
and adrenaline.
28.
29. ENZYME INDUCTION
Some P450 substrate drugs, on repeated
administration induce P450 expression by enhancing the
rate of its synthesis.
Leads to accelerated drug metabolism leading to:
Decreased plasma drug concentrations.
Decreased drug activity if metabolite is inactive.
Increased drug activity if metabolite is active.
Decreased therapeutic drug effect.
30. CLINICAL RELEVANCE
Drug- drug interaction:
Eg: Phenytoin accelerates Vitamin D3 metabolism
Osteomalacia.
Failure of OCP if potent inducers like rifampicin or
phenytoin are used.
Drug toxicity:
Eg: Risk of hepatotoxicity is more in Ethanol drinkers
than in those having Paracetamol overdose.
31. ENZYME INHIBITION
One drug may inhibit the metabolism of another drug
resulting in an increase in the circulating levels of the
slowly metabolized drug.
A drug may inhibit one isoenzyme while itself being a
substrate of another isoenzyme.
Eg: Quinidine is metabolized mainly by CYP3A4 but it
inhibits CYP2D6.
32. Inhibition of CYP isoenzyme activity is an important
source of drug interactions that leads to serious adverse
events.
Eg: Omeprazole is a potent inhibitor of 3 CYP
isoenzymes responsible for warfarin metabolism.
33.
34. Inhibition of drug metabolism
Increased plasma levels over time and with long
term medications.
Prolonged pharmacological drug effect.
Increased drug induced toxicities.
35. FIRST PASS METABOLISM
All drugs taken orally pass through GIT and portal
system before reaching the systemic circulation.
In first pass metabolism, metabolism of drugs occur
before the drug enters systemic circulation.
Net result is decreased bioavailabilty of the drug
leading to diminished therapeutic response.
38. Most drugs and drug metabolites are eliminated from
the body through renal (most common) and biliary
excretion.
Relies on the lipophilic character of the drug or
metabolite.
39. RENAL EXCRETION OF DRUGS:
Renal blood comprises 25% total systemic blood flow.
Rate of drug elimination through kidneys depend on:
balance of drug filtration
secretion
reabsorption rate.
40. Afferent arteriole Free drug and plasma protein
bound drug glomerulus.
However only the free drug is filtered into the renal
tubule.
Renal blood flow, GFR and drug binding to plasma
protein affect the amount of drug entering the tubule at
the glomerulus.
41. Rapid excretion of the drug is caused by:
Enhancing the blood flow.
Increasing the GFR
Decreasing plasma protein binding.
42.
43. GLOMERULAR FILTRATION:
Drugs enter the kidney through renal arteries which
divide to form glomerular capillary plexus.
Free drug flows through the capillary slits into the
Bowman’s space as a part of glomerular filtrate.
Glomerular capillaries allow drug molecules of
molecular weight below 20,000.
Lipid solubility and pH do not influence passage of
drugs into the glomerular filtrate.
44. TUBULAR SECRETION:
Upto 20% of renal plasma flow is filtered through the
glomerulus.
80% pass on to the peritubular capillaries of the
proximal tubules.
Here, the drug molecules are transferred to the tubular
lumen by two independent and relatively non selective
carrier systems- OAT and OCT.
OAT transports acidic drugs while OCT handles organic
bases.
45.
46. Unlike glomerular filtration, carrier mediated transport
can achieve maximal drug clearance even when most of
the drug is bound to plasma protein.
Many drugs compete for the same transport system
leading to drug interactions.
Eg: Probenecid prolongs the action of penicillin by
retarding its tubular secretion.
47. TUBULAR REABSORPTION:
The concentration of the drug increases as it moves
towards the distal convoluted tubule.
If the drug is uncharged, it may diffuse out of the
nephric lumen back into the systemic circulation.
For an ionised drug, reabsorption in the tubule can be
enhanced or inhibited by chemical adjustment of urinary
pH.
48. Weak acids can be eliminated by alkanisation of urine
while weak bases can be eliminated by acidification of
urine- ion trapping.
Eg: Phenobarbitol overdose can be treated with sodium
bicarbonate.
It alkanises the urine, keeps the drug ionised and
decreases its reabsorption.
If overdose is with a weak base, such as cocaine,
acidification of the urine with NH4Cl leads to protonation
of the drug and an increase in its clearance.
49. BILIARY EXCRETION:
Various hydrophilic drug conjugates particularly
glucuronides are concentrated in the bile and delivered
to the intestine.
Here the glucuronide is hydrolysed, releasing the active
drug once more.
This free drug is reabsorbed and the cycle is repeated-
enterohepatic circulation.
50.
51. CLEARANCE
Defined as the rate of elimination of the drug in relation
to its concentration.
Clearance = Rate of elimination
Concentration
Elimination of the drug may involve processes occuring
in the kidney, liver, lungs etc..
Clearance(total) = Clearance(renal) + Clearance (hepatic) +
Clearance(others).
52. KINETICS OF ELIMINATION
Most of the elimination reactions (includes both
metabolism and excretion) follow Michaelis- Menten
kinetics:
Rate of elimination= E= Vmax [C]
Km+ C
Where,
Vmax Maximum rate of drug elimination.
Km drug concentration at which rate of elimination is
½ Vmax (Michaelis constant).
C Concentration of the drug in the plasma.
53. FIRST ORDER KINETICS:
Here the concentration of the drug is much less than
the Michaelis constant Km.
Hence the equation reduces to,
E = Vmax [C]
Km
That is, rate of drug elimination is directly proportional
to the concentration of the free drug.
54.
55. ZERO ORDER KINETICS:
In a few drugs like aspirin, ethanol and phenytoin,
[C] is much greater than Km.
Hence the equation reduces to,
E = Vmax [C] = Vmax
[C]
Rate of elimination remains constant over time.
56. REFERENCES:
Rang and Dales pharmacology.
Basic and clinical pharmacology – Katzung.
Lippincott’s illustrated reviews.
David E Golan’s Principles of pharmacology.
Text book of clinical pharmacolgy- James Ritter
HL Sharma
KD Tripathi