This document provides an introduction and overview of bioassay and drug screening. The overall aim of the course is to teach students how to qualitatively and quantitatively estimate active substances using biological activity. By the end, students will be able to design screening experiments to assess new compound activity using in vivo, ex vivo, or in vitro models. They will also learn to identify optimum drug doses by measuring potency against a reference drug. The document outlines learning outcomes and describes different types of bioassays, drug screenings, and the importance of ethics in research using animals.
2. Overall aim of the course
• This course aims to teach students the essentials of the qualitative as well as
quantitative estimation of active substances by means of their biological activity.
• By the end of this course, students will be able to design screening experiments
to assess the activity of new compounds using either whole animals (in vivo
screening), isolated organs (ex vivo screening) or cellular models (in vitro
screening).
• In addition, they can identify develop the optimum doses of new drugs via
measuring the potency in relation to a reference drug.
• This will include different pharmacological classes of the used medications
such as analgesics, antidepressants and autonomic- acting drugs.
3. Learning outcomes of the course
By the end of this course, students should be able to:
1 Identify different types and methods used in biological screening of
new compounds withunknown biological activity to explore their
pharmacological actions. (1-1-1-1)
2 Learn how determine the concentrations and relative potency of
drugs in biological fluids. (1-1-1-1)
3 Identify different types of experimental models used in drug
standardization. (1-1-1-1)
4Identify and apply proper use of different medical terms used in
biological standardization.(1-1-2-1)
4. Learning outcomes of the course
5Develop the proper handling and disposal skills for experimental animals and ex-vivo
isolated organ preparations. (2-3-2-1)
6Effectively and accurately use different methods of biological assay in identification of site
and mechanism of actions of different drug categories. (3-2-1-1)
7 To be able to provide honest and efficient peer review and evaluation of his colleagues. (4-1-
1-1)
8 Acquire the proper and effective use of time. (4-1-2-2)
9 To be able to work in team. (4-1-2-3)
5. Estimation of the Potency or concentration of an
active principle in unit quantity of preparation
by measuring its biological response on living tissues
Bioassay
6. Drug screening
• Definition: It is the investigation of any pharmacological activity of a compound
• Types of screenings
Blind screening: to see if the drug has any significant pharmacological
activity.
Simple screening: to see if the drug has a particular
pharmacological activity e.g. if the drug has hypoglycemic or antihypertensive action.
Programmed screening: the pharmacological drug group is known, but a full
pharmacological activity isn't fully investigated, e.g. mechanism, side
• effects etc.
7. Types of blind screening:
I. Behavioral (neuropharmacology)
II. The cardiovascular test
III. The cat nictitating membrane
IV. Isolated organ preparations
Blind screening
8. The Three Rs (replacement, refinement, and reduction) have
become an internationally accepted approach for researchers
to apply when deciding to use animals in research.
Ethics in research with animals
9. Replacement refers to methods that avoid using animals (i.e., with
inanimate systems such as computer
replacing animals
programs)
Refinement refers to modifications of experimental pro•cedures to enhance
animal well-being and minimize or eliminate pain and distress
Reduction involves strategies for obtaining infor•mation from the use
of fewer animals or for maximizing the information obtained from a given number
of animals (without increasing pain or dis•tress) so that
in the long run fewer animals are needed to acquire the same scientific
information
10. U.S. Government Principles for the Utilization of Animals Used in
Research:
Arationale and purpose of the proposed use of animals
The living conditions of animals should be appropriate for their
spe•cies and contribute to their health and comfort. Normally, the
hous•ing, feeding, and care of all animals used for biomedical
purposes must be directed by a veterinarian or other scientist
trained and expe•rienced in the proper care and handling
Justification of the number of animals proposed and the use of
the minimum number required to obtain valid results as well as
avoiding unnecessary duplication of experiments
Ensure that all individuals who are using animals have received
instruction in research methods and in the care, maintenance and
handling of the species being used appropriately
11. Make reasonable efforts to minimize the discomfort, infection,
illness and pain of animal subjects
Use a procedure subjecting animals to pain or stress only when an
alternative procedure is unavailable and the goal is justified by its
prospective scientific, educational or applied value
Perform surgical procedures under appropriate anesthesia and follow
techniques to avoid infection and minimize pain during and after
surgery
Restraint devices should be suitable in size, design, and operation to
minimize discomfort, pain, distress, and the potential for injury to the
animal and the research staff and prolonged restraint should be
avoided unless it is essential for achieving research objectives
Proceed rapidly when it is appropriate that an animal's life be
terminated, with an effort to minimize pain and in accordance with
accepted procedures and dead bodies should be kept frozen until
incineration
12.
13. Contd..
Activity assayed should be the activity of interest
Standard & test sample - similar pharmacological
effects & mode of action
Both should be compared for their established
pharmacological effect using specified technique
Ex: *Ach – contractile response on frog rectus
*Histamine – contractile response on guinea
pig ileum
14. Contd…
To compare the strength of a drug obtained
from various sources due to different
compositions (Eg:Cardiac glycosides)
Chemicals with similar structure, but different
biological activity
Chemical structure of the active principle is
unknown
Chemical structure known; cannot be actively
purified. Eg: Peptide hormones
15. Bioassay can be performed on
• Intact animals
Invivo
• Isolated tissues
• Specific cells
• Organisms
Invitro
19. Quantal assay
Quantal response - the response is in the
form of "all or none", i.e. either no
response or maximum response
17
Graded assay
Graded response - response is proportional to the dose
and response may lie between no response and the
maximum response.
• Cumulative dose response
22. Indications of bioassay
No chemical method has been developed
Chemical assay is too complex /not sensitive enough to
measure (ex: insulin, Ach)
To measure the pharmacological activity of new or
chemically undefined substances
For biological standardization of drugs obtained from
natural sources as these cannot be obtained in pure
form. Eg: Oxytocin,Vasopressin,Insulin,Heparin..
23. Contd…
To compare the strength of a drug obtained
from various sources due to different
compositions (Eg:Cardiac glycosides)
Chemicals with similar structure, but different
biological activity
Chemical structure of the active principle is
unknown
Chemical structure known; cannot be actively
purified. Eg: Peptide hormones
24. Uses of Bioassay
▶ Measure the pharmacological activity of new/
chemically undefined substances
▶ Measure drug toxicity and unwanted effects
▶Determination of potency, ED50/LD50 of drugs
▶New drug development
▶Measure clinical effectiveness
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25. Characteristics of a good assay
method
▶ Sensitivity
▶ Specificity
▶ Repeatability
▶ Reproducibility
▶ Precision
▶ Accuracy
