Bioavailability refers to how much of a compound actually reaches systemic circulation and becomes available for the body (or target tissue) to use. It’s one of the most important concepts in pharmacology, drug research, and compound formulation.
Think of it like this: If you administer 100 mg of a substance, but only 40 mg makes it into circulation, the bioavailability is 40%. The rest is lost through digestion, metabolism, or first-pass liver breakdown.
Key Takeaway
Bioavailability tells you how efficiently a compound is absorbed and used. Higher bioavailability = more effective delivery.
Bioavailability Explained
Researchers look at bioavailability for one simple reason: dose does not equal delivery. Two compounds may share the same milligram amount but behave completely differently once inside the body.
Bioavailability helps determine:
How much of a compound actually works
Optimal dosing for research
Onset and intensity of effects
Comparisons between oral, sublingual, IV, IM, or transdermal routes
How quickly a compound is metabolised or cleared
It’s also crucial for understanding why certain compounds seem “weak” or “strong” at similar doses.
How Bioavailability Is Measured
In research, bioavailability is typically expressed as:
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Glossary: Bioavailability
Bioavailability refers to how much of a compound actually reaches systemic circulation and becomes available for the body (or target tissue) to use. It’s one of the most important concepts in pharmacology, drug research, and compound formulation.
Think of it like this:
If you administer 100 mg of a substance, but only 40 mg makes it into circulation, the bioavailability is 40%. The rest is lost through digestion, metabolism, or first-pass liver breakdown.
Key Takeaway
Bioavailability tells you how efficiently a compound is absorbed and used. Higher bioavailability = more effective delivery.
Bioavailability Explained
Researchers look at bioavailability for one simple reason: dose does not equal delivery.
Two compounds may share the same milligram amount but behave completely differently once inside the body.
Bioavailability helps determine:
It’s also crucial for understanding why certain compounds seem “weak” or “strong” at similar doses.
How Bioavailability Is Measured
In research, bioavailability is typically expressed as:
Further reading: Bioavailability and Bioequivalence
Modern studies may calculate it using:
These help quantify how much compound is truly available to exert a measurable effect.
Further reading: SARMs Half-life
Common Factors That Influence Bioavailability
Bioavailability varies widely depending on:
1. Route of Administration
2. Chemical Structure
Some molecules simply absorb better than others.
3. First-Pass Metabolism
The liver breaks down certain compounds aggressively before they reach circulation.
4. Solubility
Poorly water-soluble compounds typically have lower bioavailability.
5. Particle Size & Formulation
Micronisation, salts, esters, and liquid suspensions can dramatically change uptake.
Absolute vs. Relative Bioavailability
Absolute Bioavailability
Comparison of oral vs. IV delivery of the same compound.
Relative Bioavailability
Comparison of two oral formulations (e.g., capsule vs. liquid).
This helps determine which formulation is more efficient.
Bioavailability Example (Simple Visual Table)
Why Bioavailability Is Critical in Research
For researchers, bioavailability determines:
Check out: Reference grade SARMs
It also helps explain:
In short: bioavailability is the bridge between administering a compound and actually getting results.
Back to SARMS glossary
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