18 Questions
What is the primary difference between direct and indirect bioassays?
Direct bioassays measure the pharmacological activity of a drug, while indirect bioassays measure the chemical structure.
When is chemical assay preferred over bioassay?
When the chemical structure of the drug is fully known.
What is the purpose of bioassay in the standardization of drugs obtained from natural sources?
To compare the strength of the drug from various sources.
What is the purpose of comparing a test substance with the International Standard preparation?
To standardize the drug.
Why is bioassay used to measure the pharmacological activity of peptide hormones?
Because peptide hormones cannot be purified.
What is the advantage of bioassay over chemical assay in certain situations?
Bioassay can measure the pharmacological activity of a drug when the chemical structure is unknown.
What is the primary objective of bioassay?
To determine the potency of a test substance
What is the characteristic of a quantal bioassay?
An all-or-none response is observed
What is the purpose of using a standard preparation in bioassay?
To provide a reference point for comparison
What is the acceptable limit of accuracy in bioassay?
± 20% of true value
What is the characteristic of a graded bioassay?
A graded response is observed
What is the purpose of minimizing biological variation in bioassay?
To reduce the error in the measurement
What is the primary role of pharmacists?
To serve as a source of therapeutic substances and provide information about their use and actions
What has evolved over time in the concept of drug quality?
Simple checks of the final product
What is one of the responsibilities of pharmacists?
To ensure the quality of a drug
What is a key aspect of drug quality assurance?
Ensuring the stability of a drug
What is a type of test used to evaluate the quality of a drug?
All of the above
What is the goal of pharmaceutical assays?
To ensure the quality of a drug
Study Notes
Types of Bioassays
- Direct assays
- Indirect assays:
- Based on quantitative responses (Graded)
- Based on quantal responses (“all or none”; Quantal)
Comparison of Chemical and Bioassay
- Bioassay:
- Less precise
- More time-consuming
- Active constituent and structure not known
- More sensitive
- Chemical Assay:
- More precise
- Less time-consuming
- Active constituent and structure fully known
- Less sensitive
Indications of Bioassay
- Chemical method is not available or is too complex
- Insensitive to low doses (e.g., Histamine)
- Active principle cannot be isolated (e.g., insulin)
- To measure the pharmacological activity of new or chemically undefined substances
- Biological activity of drug cannot be defined by a chemical assay (e.g., Cis- and Trans- form of methyl phenidate)
- To compare the strength of a drug obtained from various sources due to different compositions
- Biological standardization of drugs obtained from natural sources
Principles of Bioassay
- Compare the test substance with the International Standard preparation
- Determine how much test substance is required to produce the same biological effect
- Activity assayed should be the activity of interest
- Standard and test sample should have similar pharmacological effects and mode of action
- Minimize biological variation by keeping experimental conditions constant
Quantal Bioassay
- All or none response in all individuals (e.g., Digitalis induced cardiac arrest in guinea pigs)
- Not precise
- Employed for: Comparison of LD50 and ED50
Graded Bioassay
- As the dose increases, there is an equivalent rise in response
- Potency is estimated by comparing test sample responses with the standard response curve
- Example: Acetylcholine producing contraction of smooth muscle of frog Rectus abdominis
Accuracy Limits of Bioassay
- Accuracy improves the efficiency of bioassay for pharmaceutical biological products
- An accuracy within ± 20% of true value is good; within ± 10% is excellent
Introduction to Concepts in Pharmaceutical Assays and Determination
- Primary role of pharmacists is to serve as a source of therapeutic substances and provide information about their use and actions
- Responsibilities of pharmacists include:
- Assuring high-quality drugs in terms of chemical identity, purity, potency, stability, efficacy, safety, and acceptability
Learn about the bioassay technique used to compare the activity of a test substance to a standard substance. Understand the importance of similar pharmacological effects and mode of action. Discover how to minimize biological variation in experiments.
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