Biopharmaceutics: Mechanisms of Drug AbsorptionSURYAKANTVERMA2
Biopharmaceutics is defined as the study of factors influencing the rate and amount of drug that reaches the systemic circulation and the use of this information to optimise the therapeutic efficacy of the drug products.
A Powerpoint presentation on drugs excretion and elimination suitable for UG medical students. This ppt is already presented to my students in one of the theory classes.
Biopharmaceutics: Mechanisms of Drug AbsorptionSURYAKANTVERMA2
Biopharmaceutics is defined as the study of factors influencing the rate and amount of drug that reaches the systemic circulation and the use of this information to optimise the therapeutic efficacy of the drug products.
A Powerpoint presentation on drugs excretion and elimination suitable for UG medical students. This ppt is already presented to my students in one of the theory classes.
Objectives for this present are to define:
terminology
explain principles of drug action
describe pharmacokinetic functions
principles of pharmacodynamics
identify adverse drug reactions
Therapeutic Drug Monitoring (TDM)
Discuss the logic for therapeutic drug monitoring, which refer to as (TDM)
List various classes of drugs that require TDM
General description of this therapeutic drag TD
Discuss the proper sample timing and method for TDM
And Discuss analytical methods available for TDM
List various drugs that not require TDM
Steady state
Therapeutic Drug Groups
Digoxin, quinidine, procainamide, disopyramide.
- Aminoglycosides (amikacin, gentamicin, kanamycin, tobramycin) - vancomycin
leucovorin rescue ?
First-pass metabolism
HPLC methods
Pharmacokinetics (PK) is the study of how the body interacts with administered substances for the entire duration of exposure (medications for the sake of this article). This is closely related to but distinctly different from pharmacodynamics, which examines the drug’s effect on the body more closely. The four main parameters generally examined by this field include absorption, distribution, metabolism, and excretion (ADME). Wielding an understanding of these processes allows practitioners the flexibility to prescribe and administer medications that will provide the greatest benefit at the lowest risk and allow them to make adjustments as necessary, given the varied physiology and lifestyles of patients.
When a provider prescribes medication, it is with the ultimate goal of a therapeutic outcome while minimizing adverse reactions. A thorough understanding of pharmacokinetics is essential in building treatment plans involving medications. Pharmacokinetics, as a field, attempts to summarize the movement of drugs throughout the body and the actions of the body on the drug. By using the above terms, theories, and equations, practitioners can better estimate the locations and concentrations of a drug in different areas of the body.
The appropriate concentration needed to obtain the desired effect and the amount needed for a higher chance of adverse reactions is determined through laboratory testing. Using the equations given above, a clinician can easily estimate safe medication dosing over a period of time and how long it will take for a medication to leave a patient’s system. These are, however, statistically-based estimations, influenced by differences in the drug dosage form and patient pathophysiology. This is why a deep understanding of these concepts is essential in medical practice so that improvisation is possible when the clinical situation requires it.
NVBDCP.pptx Nation vector borne disease control programSapna Thakur
NVBDCP was launched in 2003-2004 . Vector-Borne Disease: Disease that results from an infection transmitted to humans and other animals by blood-feeding arthropods, such as mosquitoes, ticks, and fleas. Examples of vector-borne diseases include Dengue fever, West Nile Virus, Lyme disease, and malaria.
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
Ethanol (CH3CH2OH), or beverage alcohol, is a two-carbon alcohol
that is rapidly distributed in the body and brain. Ethanol alters many
neurochemical systems and has rewarding and addictive properties. It
is the oldest recreational drug and likely contributes to more morbidity,
mortality, and public health costs than all illicit drugs combined. The
5th edition of the Diagnostic and Statistical Manual of Mental Disorders
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disorder called alcohol use disorder (AUD), with mild, moderate,
and severe subclassifications (American Psychiatric Association, 2013).
In the DSM-5, all types of substance abuse and dependence have been
combined into a single substance use disorder (SUD) on a continuum
from mild to severe. A diagnosis of AUD requires that at least two of
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The four main behavioral effects of AUD are impaired control over
drinking, negative social consequences, risky use, and altered physiological
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the systemic nature of the disease, neurocircuitry and stages of AUD,
comorbidities, fetal alcohol spectrum disorders, genetic risk factors, and
pharmacotherapies for AUD.
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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
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2. Learning Objectives
• Basic principles of pharmacokinetics
• Process of ADME
• Clinical Significance
• Enlist different processes involved in passage of
drugs through membranes.
• Define various processes of absorption of drugs.
• Explain the characteristics of absorptive processes
with examples of each.
• Enumerate factors modifying absorption of drugs.
3. Pharmacokinetics
Pharmacokinetics is the study of drug disposition
in the body.
“What the body does to the drug?”
It describes, both qualitatively and quantitatively,
the pharmacokinetic processes of absorption,
distribution, metabolism, and excretion and
their relationship to the pharmacological,
therapeutic or toxic response in human.
4.
5. Importance of PK studies
To Prevent toxicity . drugs may accumulate and produce
toxicity
Useful drugs may have no benefit because doses are too
small to establish therapy
A drug can be rapidly metabolized.
7. Is the passage of drug through cell
membranes to reach its site of action.
Mechanisms of drug absorption
1. Simple diffusion = passive diffusion.
2. Active transport.
3. Facilitated diffusion.
4. Pinocytosis (Endocytosis).
8.
9. water soluble drug (ionized or polar) is readily
absorbed via aqueous channels or pores in cell
membrane.
Lipid soluble drug (nonionized or non polar) is
readily absorbed via cell membrane itself.
10. Characters
common.
Occurs along concentration gradient
Non selective
Not saturable
Requires no energy
No carrier is needed
Depends on lipid solubility
Depends on pka of drug - pH of medium
11.
12. Occurs against concentration gradient.
Requires carrier and energy.
Specific
Saturable.
Iron absorption.
Uptake of levodopa by brain.
13.
14. Occurs along concentration gradient.
Requires carriers
Selective.
Saturable.
No energy is required.
15.
16.
17. Endocytosis: uptake of membrane-bound particles.
Exocytosis: expulsion of membrane-bound particles.
High molecular weight drugs or
Highly lipid insoluble drugs
18.
19. PKa of the drug
(Dissociation or ionization constant):
pH at which half of the substance is ionized
& half is unionized.
pH of the medium
Affects ionization of drugs.
–Weak acids best absorbed in stomach.
–Weak bases best absorbed in intestine.
20.
21.
22. Factors Affecting Bioavailability
Molecular weight of drug.
Drug Formulation (ease of dissolution).
(solution > suspension > capsule > tablet)
Solubility of the drug
Chemical instability in gastric pH
(Penicillin & insulin )
First pass metabolism reduces bioavailability
28. DRUG DISTRIBUTION
• It is the process by which a drug diffuses or
transferred from intravascular to extravascular
space.
• These spaces are described mathematically as
volume of distribution(Vd).
29.
30. Drug Distribution
• Very little of the drug is in contact with receptors at any given
time
• Most of the drug is in areas remote from the site of action (of
interest), such as
– Plasma binding sites
– Muscle tissue
– Adipose tissue (fat)
– Liver
– Kidneys
31.
32.
33.
34.
35.
36. Metabolism
• Liver is the primary site for metaboloism.
• Most of the drugs are inactivated by metabolism.
• Some drugs may be activated from the inactive compunds (Prodrugs)
and others may give rise to active metabolites from the active compound.
• Metabolism may occur with help of microsomal or non-microsomal
enzymes.
• Microsomal enzymes (monooxygenase, cytochrome P450 and glucoronyl
transferase) may be induced or inhibited by other drugs whereas non-
microsomal enzymes are not subjected to these interactions.
37. Enzyme inducers
• Increases the metabolism of other drugs and reduce
their effect.
G Griseofulvin
P Phenytoin
R Rifampicin
S Smoking
Cell Carbamazepine
Phone Phenobarbitone
39. Prodrug
Few drugs are inactive as such and
need conversion in the body to one
or more active metabolites. Such a
drug are called a prodrug .
The prodrug may offer advantages
over the active form in being more
stable, having better bioavailability
or other desirable pharmacokinetic
properties or less side effects and
toxicity.
Some prodrugs are activated
selectively at the site of action.
40. Phases of Drug Metabolism
• Phase I (non-synthetic) – in this reaction functional
group get attached with drug molecule.
After phase I reaction, drug may become water
soluble or lipid soluble.
• Phase II (synthetic) – in this reaction a conjugate is
attached to drug and make it water soluble.
41. Metabolic Reactions
Phase I (non-synthetic) Phase II (synthetic)
Functional group get attached with
drug molecule
Conjugate is attached to drug .
Drug may become water soluble
or lipid soluble.
Make it water soluble
Include oxidation, reduction,
hydrolysis, cyclization, and
decyclization etc.
Include glucuronidation,
acetylation, methylation,
sulfation,and glycine
conjugation etc.
42.
43. Excretion
• Kidney is the major route of excretion.
• Excretion through kidneys occurs by glomerular filtration, tubular
reabsorption and tubular secretion.
• Glomerular filtration depend on the plasma protein binding and
renal blood flow.
• It does not depend on the lipid solubility because all substances
(wether water soluble or lipid soluble) can cross fenestrated
glomerular membrane.
• Tubular reabsorption depends on lipid solubility.
• If a drug is lipid soluble, more of it will be reabsorbed and less will
be excreted. Opposite is true for lipid insoluble drugs.
44. Excretion
• As lipid solubility depends on ionization, the ionized drug
will be excreted by the kidney.
• Thus, in acidic drug poisoning (salicylate, barbiturates
etc.) urine should be alkalinized with sodium bicarbonate
because weak acids are in ionized from in alkaline urine
and thus are easily excreted.
• Similarly for basic drug poisoning (e.g. morphine,
amphetamine etc.), urine should be acidified using
ammonium-chloride.
45. Excretion
Tubular secretion
• Does not depend on lipid solubility or plasma protein binding.
• In the nephron, separate pumps are present for acidic and basic
drugs.
• Drugs utilizing the same transporter may show drug
interactions e.g. Probenecid decreases the excretion of
penicillin and increases the excretion of uric acid.
• Remember, exogenous substances e.g. Penicillins are removed
whereas endogenous substances like uric acid are retained by
these pumps.
46. Kinetics Of Elimination
• Rate of elimination is the amount of drug eliminated (in
units of weight like grams) per unit time.
• If it is seen as a function of plasma concentration, we
derive an important parameter known as clearance (CL).
• Thus clearance is the rate of elimination of a drug
divided by its plasma concentration.
47. First Order kinetics
(Linear kinetics)
Zero Order kinetics
(Non linear kinetics)
1. Constant fraction of drug is eliminated per
unit time.
2. Rate of elimination is proportional to
plasma concentration.
3. Clearance remains constant.
4. Half life remain constant.
5. Most of the drugs follow first order
kinetics.
1. Constant amount of the drug is
eliminated per unit time.
2. Rate of elimination is independant of
plasma concentration.
3. Clearance is more at low
concentrations and less at high conc.
4. Half life is less at low conc. and more
at high conc.
5. Very few drugs follow pure zero order
kinetics e.g. alcohol.
6. Any drug at high conc. (when metabolic
or elimination pathway is saturated)
May show zero order kinetics.
48.
49. Plasma half-life
1. The Plasma half-life (t1/2) of a drug
is the time taken for its plasma
concentration to be reduced to half of
its original value.
• initial rapidly declining (α) phase-due
to distribution.
• later less declined (β) phase-due to
elimination.
2. At least two half-lives (distribution t1/2
and elimination t1/2) can be calculated
from the two slopes.
3. The elimination half life derived from
the β slope is simply called the 'half
life' of the drug.
50.
51. Dose strategy
• The drugs having high volume of distribution are given by this
strategy.
• First a large dose (loading dose) is administered to attain the steady
state quickly and later on, to maintain the plasma concentration
smaller dose is given (maintenance dose).
• Loading dose : it is given to load (saturate) the tissue stores. So it is
mainly dependent on V d .
Loading dose = V d x Target plasma concentration
52. Therapeutic Drug Monitoring (TDM)
• TDM is a process by which the dose of a drug is adjusted according to
its plasma concentration.
• It is done for drugs having wide variation in pharmacokinetics ,both
intra- as well as inter- individual.
• It is done for the drugs having low therapeutic index like theophylline,
lithium, antiepileptics, immuno-modulators and anti-arrhythmics etc.
• TDM is done for those whose effect cannot be easily measured (like
effect of antihypertensive drugs can be easily measured by monitoring
BP, so TDM is not used).
• TDM is not done for the drugs which are activated in the body or
produce active metabolites (Prodrugs).
53. Fixed dose ratio combination preparations
Advantages
1. Convenience and better patient compliance.
2. Certain drug combinations are synergistic, e.g. sulfamethoxazole +
trimethoprim; levodopa + carbidopa/benserazide; combination oral
contraceptives.
3. The therapeutic effect of two components being same may add up while
the side effects being different may not, e.g. amlodipine + atenolol as
antihypertensive.
4. The side effect of one component may be counteracted by the other,
e.g. a thiazide + a potassium sparing diuretic.
5. Combined formulation ensures that a single drug will not be
administered. This is important in the treatment of tuberculosis and
HIV-AIDS.
54. Disadvantages of fixed dose ratio combinations
1. The patient may not actually need all the drugs present in a combination
2. The dose of most drugs needs to be adjusted and individualised. When a combined
formulation is used, this cannot be done without altering the dose of the other
component(s).
3. The time course of action of the components may be different: administering them at the
same intervals may be inappropriate.
4. Altered renal or hepatic function of the patient may differently affect the
pharmacokinetics of the components.
5. Adverse effect, when it occurs, cannot be easily ascribed to the particular drug causing it.
6. Contraindication to one component (allergy, other conditions) contraindicates the whole
preparation.
7. Confusion of therapeutic aims and false sense of superiority of two drugs over one is
fostered, specially in case of antimicrobials whose combinations should be avoided.
Corticosteroids should never be combined with any
other drug meant for internal use.
58. Buffering Local anaesthetics
• The potential benefits of buffering local anesthetic solutions prior to
injection, such as decreased injection pain, faster onset, and greater depth
of anesthesia, may be particularly advantageous in patients who have
difficulty achieving profound anesthesia for clinical dentistry, and for
anesthetizing infected areas.
• Dentists can effectively buffer local anesthetic preparations, using
commercially available mixing systems or by utilizing a hand-mixing
technique.
• Rather than using a remove and replace technique, practitioners may
consider a direct injection technique, adding 0.1 mL of 8.4% sodium
bicarbonate directly into any local anesthetic cartridge regardless of local
anesthetic concentration.
59. • In a study, 70% of participants achieved pulpal
anesthesia in just 1:57 minutes on average
after administration of buffered lidocaine,
versus 8:30 minutes in patients receiving
unbuffered lidocaine.
63. Bibliography
• Essentials of Medical Pharmacology -7th edition by KD Tripathi
• Goodman & Gilman's the Pharmacological Basis of Therapeutics 12th
edition by Laurence Brunton (Editor)
• Lippincott's Illustrated Reviews: Pharmacology - 6th edition by Richard A.
Harvey
• Basic and Clinical pharmacology 11th edition by Bertram G Katzung
• Rang & Dale's Pharmacology -7th edition
by Humphrey P. Rang
• Clinical Pharmacology 11th edition By Bennett and Brown, Churchill
Livingstone
• Principles of Pharmacology 2nd edition by HL Sharma and KK Sharma
• Review of Pharmacology by Gobind Sparsh
• Internet web.