The key difference between bioavailability and bioequivalence is that bioavailability is the amount of a drug that enters the bloodstream and is available for biological action at the site of action, while bioequivalence is a measure of how similar two different formulations of the same drug are in terms of their bioavailability.
Bioavailability and bioequivalence are two important concepts in pharmacology related to the absorption and availability of drugs for biological action.
CONTENTS
1. Overview and Key Difference
2. What is Bioavailability
3. What is Bioequivalence
4. Similarities – Bioavailability and Bioequivalence
5. Bioavailability vs. Bioequivalence in Tabular Form
6. FAQ – Bioavailability and Bioequivalence
7. Summary – Bioavailability vs. Bioequivalence
What is Bioavailability?
In pharmacology, bioavailability measures the rate and extent of the administered drug reaching the bloodstream to be available for biological action at the site of action. It is typically expressed as a percentage of the administered dose. For example, if a drug has a bioavailability of 80%, 80% of the drug administered will reach the bloodstream and be available for action. Bioavailability is important because it affects the effectiveness and safety of a drug. A drug with low bioavailability may not be effective because it does not reach enough concentration at the site of action. Conversely, a drug with high bioavailability may be more likely to cause side effects because it reaches a high concentration in the bloodstream.
Figure 01: The Area under the Curves of Intravenous Administration and Oral Administration
Factors such as route of administration, pharmaceutical formulation, and physiological factors influence the bioavailability of a drug. Intravenous administration is considered the most effective route since it results in 100% bioavailability due to the direct delivery of the drug into the systemic circulation. The oral route is considered the least effective in bioavailability since it is heavily associated with first-pass metabolism.
Bioavailability is typically measured by comparing the plasma concentration-time curve while the area under the curve (AUC) represents bioavailability. A higher AUC indicates higher bioavailability. Furthermore, bioavailability has significant clinical implications in drug therapies. It influences the therapeutic efficacy, safety profile, and dosing requirement of the drug. Various strategies can enhance bioavailability, such as formulating drugs as solutions or suspensions, utilizing prodrugs, and co-administration of absorption enhancers.
What is Bioequivalence?
In pharmacology, bioequivalence determines whether two different formulations of the same drugs are interchangeable. It is a relative measurement that compares the rate and extent to which the active ingredient in two formulations becomes available at the site of action. The two drugs are considered bioavailable if they have similar rates and extents of pharmacokinetics and pharmacodynamics parameters, implying that they will produce the same therapeutic effect and side effects. Bioequivalence is typically established by considering pharmacodynamics and pharmacokinetics parameters in clinical trials. During these clinical trials, area under the dose-time curve, peak concentration, and time-to-peak concentration will be mainly considered.
Figure 02: The Bioequivalence Profile of Two Bupropion Produced by Impax Laboratories and GlaxoSmithKline
Bioequivalence is essential to ensure the safety and efficacy of generic drugs that are intended to be therapeutically equivalent to their brand-name counterparts. Furthermore, these studies also allow for interchangeability between brand-name and generic formulations, providing patients with more affordable treatment options without affecting their health.
What are the Similarities Between Bioavailability and Bioequivalence?
- Bioavailability and bioequivalence are associated with drug safety and therapeutic efficacy.
- Both are measured using pharmacokinetic parameters, such as the area under the concentration-time curve (AUC), peak concentration (Cmax), and time to peak concentration (Tmax).
- Both are affected by factors such as formulation, route of administration, and individual physiology.
What is the Difference Between Bioavailability and Bioequivalence?
Bioavailability and bioequivalence are terms commonly used in pharmacology to describe different aspects related to the effectiveness and behaviour of drugs. Bioavailability measures the rate and extent of the administered drug that reaches the bloodstream to be available for biological action at the site of action. In contrast, bioequivalence measures how similar two different formulations of the same drug are regarding their bioavailability. Thus, this is the key difference between bioavailability and bioequivalence.
Bioavailability measures the amount and speed at which a drug is absorbed and reaches the bloodstream in its active form after administration compared to the drug given intravenously, directly entering the bloodstream. Furthermore, it measures the amount and speed at which a drug is absorbed and reaches the bloodstream in its active form after administration. Bioavailability is essential for investigational new drug applications (IND), new drug applications (NDA) and NDA supplements. In contrast, bioequivalence is important for generic drugs to demonstrate bioequivalence to their brand-name counterparts to ensure they perform similarly in the body. Bioequivalence data are essential for abbreviated new drug applications (ANDA).
Below is a summary of the difference between bioavailability and bioequivalence in tabular form for side-by-side comparison.
FAQ: Bioavailability and Bioequivalence
What is bioavailability in simple terms?
Bioavailability measures the rate and extent of the administered drug that reaches the bloodstream to be available for biological action at the site of action.
What is the meaning of bioequivalence?
Bioequivalence measures how similar two different formulations of the same drug are in terms of their bioavailability.
What are the applications of Bioavailability and Bioequivalence in drug development?
Bioavailability is essential for investigational new drug applications (IND), new drug applications (NDA) and NDA supplements. Bioequivalence data are essential for abbreviated new drug applications (ANDA).
Summary – Bioavailability vs. Bioequivalence
Bioavailability refers to the rate and extent at which a drug reaches the bloodstream and becomes available for biological action at the site of action. It measures the absorption and availability of a drug in the body and is crucial for drug efficacy and safety. In contrast, bioequivalence assesses how similar two different formulations of the same drug are regarding their bioavailability. It ensures that generic drugs perform similarly to their brand-name counterparts. Bioavailability studies are exploratory, while bioequivalence studies are confirmatory or statutory, and both contribute significantly to drug development, safety, and therapeutic effectiveness. Additionally, while bioavailability data can be used to assess bioequivalence, bioequivalence studies are vital for abbreviated new drug applications (ANDA) compared to the broader application scope of bioavailability in investigational new drug applications (IND), new drug applications (NDA), and NDA supplements. Thus, this is the summary of the difference between bioavailability and bioequivalence.
Reference:
1. Chow, Shein‐Chung. “Bioavailability and bioequivalence in drug development.” WIREs Computational Statistics, vol. 6, no. 4, 2014, pp. 304–312.
Image Courtesy:
1. “AUC IVPO” By Alfie↑↓© – Own work (CC0) via Commons Wikimedia
2. “Bupropion bioequivalency comparison” By CMBJ – Own work based on FDA data (CC BY 3.0) via Commons Wikimedia
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