This document discusses the pharmacokinetics of drug absorption and distribution. It begins by defining pharmacokinetics as the quantitative study of how the body acts on drugs. It then discusses the different mechanisms of drug transportation across cell membranes, including passive diffusion, filtration, and carrier-mediated transport like facilitated diffusion and active transport. It describes factors that affect drug absorption like solubility, concentration, and route of administration. It also discusses concepts like bioavailability, bioequivalence, distribution, redistribution, barriers to drug movement, and plasma protein binding. In summary, it provides an overview of how drugs move into, through, and out of the body after administration.
Pharmacokinetics is the study of the movement of drug molecules in the body. It includes absorption, distribution, metabolism, and excretion of drugs. Pharmacokinetics is the study of what happens to drugs once they enter the body (the movement of the drugs into, within, and out of the body). For a drug to produce its specific response, it should be present in adequate concentrations at the site of action. This depends on various factors apart from the dose.
Four pharmacokinetic properties determine the onset, intensity, and the duration of drug action (Figure 1.6.1):
• Absorption: First, absorption from the site of administration permits entry of the drug (either directly or indirectly) into plasma.
• Distribution: Second, the drug may then reversibly leave the bloodstream and distribute it into the interstitial and intracellular fluids.
• Metabolism: Third, the drug may be biotransformed by metabolism by the liver or other tissues.
• Elimination: Finally, the drug and its metabolites are eliminated from the body in urine, bile, or feces.
In short, pharmacokinetics means what the body does to the drug.
Pharmacokinetics is the study of the movement of drug molecules in the body. It includes absorption, distribution, metabolism, and excretion of drugs. Pharmacokinetics is the study of what happens to drugs once they enter the body (the movement of the drugs into, within, and out of the body). For a drug to produce its specific response, it should be present in adequate concentrations at the site of action. This depends on various factors apart from the dose.
Four pharmacokinetic properties determine the onset, intensity, and the duration of drug action (Figure 1.6.1):
• Absorption: First, absorption from the site of administration permits entry of the drug (either directly or indirectly) into plasma.
• Distribution: Second, the drug may then reversibly leave the bloodstream and distribute it into the interstitial and intracellular fluids.
• Metabolism: Third, the drug may be biotransformed by metabolism by the liver or other tissues.
• Elimination: Finally, the drug and its metabolites are eliminated from the body in urine, bile, or feces.
In short, pharmacokinetics means what the body does to the drug.
This presentation will give the students a basic knowledge about the pharmacokinetics of durgs. It will help them clear the basics before digging deep into the topic.
The extent and rate at which its active moiety is delivered from pharmaceutical form and becomes available in the systemic circulation
Two related drugs are bioequivalent if they show comparable bioavailability and similar times to achieve peak blood concentrations.
The therapeutic index of a drug is the ratio of the dose that produces toxicity to the dose that produces a clinically desired or effective response in a population of individuals:
“ Bioavailability-
means the rate and extent to which the active ingredient or active moiety is absorbed from a drug product and becomes available at the site of action."
This presentation will give the students a basic knowledge about the pharmacokinetics of durgs. It will help them clear the basics before digging deep into the topic.
The extent and rate at which its active moiety is delivered from pharmaceutical form and becomes available in the systemic circulation
Two related drugs are bioequivalent if they show comparable bioavailability and similar times to achieve peak blood concentrations.
The therapeutic index of a drug is the ratio of the dose that produces toxicity to the dose that produces a clinically desired or effective response in a population of individuals:
“ Bioavailability-
means the rate and extent to which the active ingredient or active moiety is absorbed from a drug product and becomes available at the site of action."
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Pharmacokinetics of Drug_Pharmacology Course_Muhammad Kamal Hossain.pptxMuhammad Kamal Hossain
Pharmacokinetics is defined as the kinetics of drug absorption, distribution, metabolism and excretion (ADME) and their relationship with the pharmacological, therapeutic or toxicological response in man and animals.
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Pharmacokinetics - drug absorption, drug distribution, drug metabolism, drug ...http://neigrihms.gov.in/
A power point presentation on general aspects of Pharmacokinetics suitable for undergraduate medical students beginning to study Pharmacology. Also suitable for Post Graduate students of Pharmacology and Pharmaceutical Sciences.
Presentation covers the basics of pharmacokinetic. Mechanism for the transport of drug molecule. Absorption, factors affecting on absorption of drugs. Concept of bioavailability. Distribution, plasma protein binding, tissue binding, barriers.
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Defecation
Normal defecation begins with movement in the left colon, moving stool toward the anus. When stool reaches the rectum, the distention causes relaxation of the internal sphincter and an awareness of the need to defecate. At the time of defecation, the external sphincter relaxes, and abdominal muscles contract, increasing intrarectal pressure and forcing the stool out
The Valsalva maneuver exerts pressure to expel faeces through a voluntary contraction of the abdominal muscles while maintaining forced expiration against a closed airway. Patients with cardiovascular disease, glaucoma, increased intracranial pressure, or a new surgical wound are at greater risk for cardiac dysrhythmias and elevated blood pressure with the Valsalva maneuver and need to avoid straining to pass the stool.
Normal defecation is painless, resulting in passage of soft, formed stool
CONSTIPATION
Constipation is a symptom, not a disease. Improper diet, reduced fluid intake, lack of exercise, and certain medications can cause constipation. For example, patients receiving opiates for pain after surgery often require a stool softener or laxative to prevent constipation. The signs of constipation include infrequent bowel movements (less than every 3 days), difficulty passing stools, excessive straining, inability to defecate at will, and hard feaces
IMPACTION
Fecal impaction results from unrelieved constipation. It is a collection of hardened feces wedged in the rectum that a person cannot expel. In cases of severe impaction the mass extends up into the sigmoid colon.
DIARRHEA
Diarrhea is an increase in the number of stools and the passage of liquid, unformed feces. It is associated with disorders affecting digestion, absorption, and secretion in the GI tract. Intestinal contents pass through the small and large intestine too quickly to allow for the usual absorption of fluid and nutrients. Irritation within the colon results in increased mucus secretion. As a result, feces become watery, and the patient is unable to control the urge to defecate. Normally an anal bag is safe and effective in long-term treatment of patients with fecal incontinence at home, in hospice, or in the hospital. Fecal incontinence is expensive and a potentially dangerous condition in terms of contamination and risk of skin ulceration
HEMORRHOIDS
Hemorrhoids are dilated, engorged veins in the lining of the rectum. They are either external or internal.
FLATULENCE
As gas accumulates in the lumen of the intestines, the bowel wall stretches and distends (flatulence). It is a common cause of abdominal fullness, pain, and cramping. Normally intestinal gas escapes through the mouth (belching) or the anus (passing of flatus)
FECAL INCONTINENCE
Fecal incontinence is the inability to control passage of feces and gas from the anus. Incontinence harms a patient’s body image
PREPARATION AND GIVING OF LAXATIVESACCORDING TO POTTER AND PERRY,
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VISION
Being proactive
Supporting optimal animal and human health
Exploring ways to reduce overall use of antimicrobials
Using the drugs that prevent and treat disease by killing microscopic organisms in a responsible way
GOAL
to prevent the generation and spread of antimicrobial resistance (AMR). Doing so will preserve the effectiveness of these drugs in animals and humans for years to come.
being to preserve human and animal health and the effectiveness of antimicrobial medications.
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to prevent antimicrobial overuse, misuse and abuse.
to minimize the developme
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2. Content
Pharmacokinetics
Membrane transporters
Absorption
Bioavaliability
Bioequivalence
Distribution
Redistribution
Barriers
Plasma protein binding
Absoption and Distribution
3. Pharmacokinetics
How the human body acts on the drugs?
• It is the quantitative study of drug movement in,
through and out of the body. Intensity of the effect is
related to concentration of the drug at the site of
action, which depends on its pharmacokinetics
properties.
• Pharmacokinetic properties of particular drug is
important to determine the route of administration,
dose, onset of action, peak action time, duration of
action and frequency of dosing.
4.
5.
6. Drug Transportation
Drug molecules can cross cell membrane by:
I. Passive diffusion
II. Filteration
III. Protein-mediated transport (carrier mediated)
Facilitated transport
Active transport : Primary and Secondary
transport
Antiport
Symport
7. Passive Transport
• Majority of drugs diffuse across the membrane in the
direction of concentration gradient.
• It is proportional to lipid : water partition coefficient.
• Lipid soluble drugs diffuse by dissolving in the lipoidal
matrix of the membrane.
• It does not require energy and carriers for the
transportation process.
• There are various factors which affect passive transport:
Size of the molecule
Lipid solubility
Polarity
Drugs which are unionized, low polarity and higher lipid
solubility can easily cross the membrane and vice-versa
8. Filtration
• Filtration is passage of drugs through aqueous pores in
the membrane or through paracellular spaces.
• Lipid-insoluble drugs cross biological membranes by
filtration if their molecular size is smaller than the
diameter of the pores.
• Majority of cells (intestinal mucosa, RBC, etc.) have
very small pores (4 Å) and drugs with MW > 100 or
200 are not able to penetrate.
• Diffusion of drugs across capillaries is dependent on
rate of blood flow through them rather than on lipid
solubility of the drug or pH of the medium.
9.
10. Specialized/ Carrier mediated
transport
• It involves specific membrane proteins for transport
known as drug transporters or carriers. These are
specific for the substrates.
• Drug molecules bind to the transporter, translocate
across the membrane and then released on the other
side of the membrane.
• It is very specific and saturable.
• Depending on the energy requirement, it can be either
Facilitated (passive) or Active Transport.
11. Facilitated diffusion
• The transporter, belonging to the super-family of solute
carrier (SLC) transporters, operates passively without
needing energy and translocates the substrate in the
direction of its electrochemical gradient, i.e. from
higher to lower concentration.
• It facilitates permeation of a poorly diffusible substrate,
e.g. the entry of glucose into muscle and fat cells by
the glucose transporter GLUT 4.
12. Active Transport(energy
dependent)
• It requires energy, is inhibited by metabolic poisons, and transports
the solutes against its electrochemical gradient (low to high
concentration ).
• E.g. levodopa and methyl dopa are actively absorbed from the gut
by the aromatic amino acid transporter .
• Primary active transport - Energy is obtained directly by the
hydrolysis of ATP.
• Secondary active transport – it utilize energy stored in voltage and ion
gradients generated by a primary active transporter . In this type of
active transport effected by another set of SLC transporters, the energy
to pump one solute is derived from the downhill movement of another
solute(e.g. Na+/K+ ATPase).
• Symport-both the solutes move in the same direction
(Cotransporters)
• Antiport-both the solutes move in opposite directions (Exchangers)
13.
14. Pinocytosis
It is the process of transport across the cell in particulate
form by formation of vesicles. This is applicable to
proteins and other big molecules, and contributes little
to transport of most drugs, barring few like vit B12 which
is absorbed from the gut after binding to intrinsic factor
(a protein).
15. Absorption
It is movement of the drug from its site of administration into the circulation
• Factors affecting absorption
1. Aqueous solubility - For poorly water soluble drugs (aspirin,
griseofulvin) rate of dissolution governs rate of absorption. A drug
given as liquid solution is absorbed faster than when the same is given
in solid form or as oily solution
2. Concentration - Drug given as concentrated solution is absorbed
faster than from dilute solution
3. Area of absorbing surface - Larger is the surface area, faster is the
absorption
16. 4. Vascularity of the absorbing surface – Blood circulation removes the
drug from the site of absorption and maintains the concentration
gradient across the absorbing surface. Increased blood flow hastens
drug absorption just as wind hastens drying of clothes.
5. Route of administration - This affects drug absorption, because each
route has its own peculiarities.
FOR ORAL ROUTE
Nonionized lipid soluble drugs, e.g. ethanol are readily absorbed
from stomach as well as intestine at rates proportional to their
lipid : water partition coefficient.
Acidic drugs, e.g. salicylates, barbiturates, etc. are predominantly
unionized in the acid gastric juice and are absorbed from
stomach, while basic drugs, e.g. morphine, quinine, etc. are
largely ionized and are absorbed only on reaching the duodenum
Particle size of the drug in solid dosage form governs rate of
dissolution. Higher the disintegration and dissolution greater be
will the absorption
Presence of food dilutes the drug and retards absorption.
17. Absorption via Subcutaneous and Intramuscular route
Absorption from s.c. Site is slower than that from i.m. site,
but both are generally faster and more consistent/
predictable than oral absorption.
Application of heat and muscular exercise accelerate drug
absorption by increasing blood flow, while
vasoconstrictors, e.g. adrenaline injected with the drug
(local anaesthetic) retard absorption.
Absorption via Topical sites (skin, cornea, mucous
membranes)
Systemic absorption after topical application depends
primarily on lipid solubility of drugs. However, only few
drugs significantly penetrate intact skin.
18.
19.
20.
21. Bioavaliability
Bioavailability refers to the rate and
extent of absorption of a drug from a
dosage form as determined by its
concentration-time curve in blood
It is a measure of the fraction (F) of
administered dose of a drug that
reaches the systemic circulation in
the unchanged form.
Bioavailability of drug injected i.v. is
100%, but is frequently lower after
oral ingestion because—
(a) the drug may be incompletely
absorbed.
(b) the absorbed drug may undergo
first pass metabolism in the
intestinal wall/liver or be excreted in
bile.
22.
23. Concept of Critical Threshold
MEC (Minimum Effective Concentration):
The minimum level of drug concentration needed for the desired
therapeutic effect to be present.
MSC (Maximum Safe Concentration): The maximum level of
drug concentration above which toxic effects occurs OR
(Minimum Toxic Concentration) MTC : The minimum level
of drug concentration that produces toxic effects.
Maximal Effect: Greatest response that can be produced by a
drug, above which no further response can be created
(sometimes called “peak effect”)
Onset: How long before a drug is able to exert a therapeutic
effect
Duration: How long a drug effect lasts
AUC is the area under the plot of plasma concentration of drug
against time after drug administration.
DRUG HALF-LIFE (t1/2 ): Half life is the time required to
reduce the plasma concentration to 50% of its original value
24.
25. Bioequivalence
Oral formulations of a drug from different
manufacturers or different batches from the same
manufacturer may have the same amount of the drug
(chemically equivalent) but may not yield the same
blood levels—biologically inequivalent.
Two preparations of a drug are considered
bioequivalent when the rate and extent of
bioavailability of the active drug from them is not
significantly different under suitable test conditions.
26. DISTRIBUTION
Once a drug has gained access to the blood stream, it
gets distributed to other tissues that initially had no
drug, concentration gradient being in the direction of
plasma to tissues. The extent and pattern of
distribution of a drug depends on its:
• lipid solubility
• ionization at physiological pH (a function of its pKa)
• extent of binding to plasma and tissue proteins
• presence of tissue-specific transporters
• differences in regional blood flow.
27. Apparent volume of distribution (V)
The volume that would accommodate all the
drug in the body, if the concentration
throughout was same as in plasma”. It is
expressed in Litres.
• Chloroquine – 13000 L, Digoxin – 420 L,
Morphine – 250 L, Propranolol – 280 L,
Streptomycin and Gentamycin – 18 L
Vd= dose administered (i.v)÷ plasma
concentration
28. Redistribution
Highly lipid-soluble drugs get initially distributed to organs
with high blood flow, i.e. brain, heart, kidney, etc.
Later, less vascular but more bulky tissues (muscle, fat)
take up the drug—plasma concentration falls and the drug
is withdrawn from the highly perfused sites.
If the site of action of the drug was in one of the highly
perfused organs, redistribution results in termination of
drug action.
Greater the lipid solubility of the drug, faster is its
redistribution.
E.g : Anaesthetic action of thiopentone sod. injected i.v. is
terminated in few minutes due to redistribution.
29. Barriers
Entry into CNS –
Entry of drugs into CNS is controlled by blood brain barrier (BBB).
It exists between plasma and extracellular surface of brain. It is
constituted by glial cells and capillary endothelium in the brain.
Only lipid soluble drugs pass through this barrier.
• Entry into foetal circulation –
Entry of drugs into foetal circulation is controlled by blood
placental barrier (BPB). It exists between maternal and foetal
circulation. It permits the entry of only lipid soluble drugs.
30. Plasma protein binding
Most drugs possess physicochemical affinity for plasma
proteins and get reversibly bound to these.
Acidic drugs generally bind to plasma albumin
Basic drugs to α1 acid glycoprotein.
31.
32. The clinically significant implications of plasma protein binding
I. Highly plasma protein bound drugs are largely restricted to the vascular
compartment because protein bound drug does not cross membranes. They
tend to have smaller volumes of distribution.
II. The bound fraction is not available for action. However, it is in equilibrium
with the free drug in plasma and dissociates when the concentration of the
latter is reduced due to elimination.
III. High degree of protein binding generally makes the drug long acting, because
bound fraction is not available for metabolism or excretion
IV. The generally expressed plasma concentrations of the drug refer to bound as
well as free drug.
V. One drug can bind to many sites on the albumin molecule. Conversely, more
than one drug can bind to the same site. This can give rise to displacement
interactions among drugs bound to the same site(s). Some clinically
important displacement interactions are: Aspirin displaces sulfonylureas,
Indomethacin, phenytoin displace warfarin.
VI. In hypoalbuminemia, binding may be reduced and high concentrations of
free drug may be attained, e.g. phenytoin and furosemide.
33. Tissue storage
Drugs may also accumulate in specific organs by active
transport or get bound to specific tissue constituents.
Drugs sequestrated in various tissues are unequally
distributed, tend to have larger volume of distribution
and longer duration of action.