DEFINITION of 'Bioavailability'

The speed and potency at which a drug enters the bloodstream. Bioavailability is affected by many things, from the way a drug is designed and produced to a patient’s genetic makeup. A drug’s bioavailability is a key factor in how well it helps a patient and in whether it causes unwanted side effects.

BREAKING DOWN 'Bioavailability'

Two drugs with the same amounts of the same active ingredients will not necessarily have the same bioavailability because of differences in the drugs’ inactive ingredients. This possible difference is one reason why generic drugs must be tested and approved before they can be marketed as name-brand equivalents. If two drugs with the same active ingredients do have the same bioavailability, they are said to be bioequivalent. If the same patient takes both drugs, they should not be able to tell the difference in the way each drug affects their body. If a drug company manufacturing a generic is having trouble creating a drug with the same bioavailability as the original, the company’s profits and stock price may suffer.

Drugs have different levels of bioavailability. Drugs taken by mouth generally have low bioavailability because they have to pass through the intestinal wall and the liver before reaching the bloodstream. A patient’s age, gender, health conditions, surgical history, stress levels, diet, physical activity levels and other drugs can all increase or decrease bioavailability. In addition, a drug can be taken many ways: as a pill, injection, patch, inhaler, eye drop, nasal spray and more. Each route of administration creates different potential levels of drug bioavailability in the human body. Drugs injected into a vein are 100% bioavailable since they are delivered directly to the bloodstream; drugs taken by any other method are less than 100% bioavailable because they have to pass through some other part of the body before entering the bloodstream. The technical term scientists use to describe bioavailability is “area under the plasma-concentration time curve.”

  1. Bioequivalence

    A similarity between two drugs meaning that they both have the ...
  2. Drug

    A substance that cures, treats, prevents or reduces the symptoms ...
  3. Abbreviated New Drug Application ...

    A written request to the U.S. Food and Drug Administration to ...
  4. New Drug Application (NDA)

    The final step formally taken by a drug sponsor, wherein it applies ...
  5. Blockbuster Drug

    An extremely popular drug that generates annual sales of at least ...
  6. Phase 2

    The second phase of clinical trials or studies for an experimental ...
Related Articles
  1. Insights

    How Pharmaceutical Companies Price Their Drugs

    Learn more about how pharmaceutical companies price drugs, why prices are often very high and why it can be difficult to settle on a suitable price.
  2. Investing

    Pharma Balks at German Price Control (BAYRY, RHHBY)

    Drug makers are worried about a proposed new German law that would tighten price controls on prescription drugs.
  3. Insurance

    Why Do Prescription Drugs Cost So Much?

    In 1975, it cost about $100 million in 2005 dollars to develop one drug from the lab to FDA approval. By 2005, that figure was $1.3 billion.
  4. Investing

    Cost of Old Cancer Drugs Rises in EU Amid Outcry

    The prices of several off-patent cancer drugs have soared more than 100% in Europe.
  5. Investing

    Drug Prices: Name Brands Doubled in Last 5 Years (ESRX)

    Express Scripts' Drug Trends Report, released Monday, revealed that the average price of brand name drugs rose 16.2% in 2015, with over one third of brand name drugs seeing price increases over ...
  6. Investing

    Drug Approvals Fell to Six-Year Low in 2016

    New drug approvals dropped to modest levels in 2016 following highs in 2014 and 2015.
  7. Insurance

    The Cancer (and Other Drug) Shortage

    Your doctor may not tell you, but even in the U.S., life-saving drugs can be in short supply. Here's what to know and do.
  8. Retirement

    How to Pick the Best Medicare Part D Plan for You

    In choosing a Medicare Part D plan, here’s a helpful step-by-step guide to what you need to know to get the drugs you need at the price you can afford.
  9. Insights

    Why Are Prescription Drug Prices So High?

    Expensive drugs that don’t have affordable alternatives or generic equivalents are a serious concern today. So why are prescription drug prices so high?
  10. Insights

    The Industry Handbook: Pharma Industry

    Learn about the pharmaceutical industry and discover the forces that influence this highly profitable and dynamic sector.
  1. How does the profit margin compare for a generic drug versus a brand name drug?

    Learn how the profit margins compare for generic drugs and brand-name drugs. Brand-name drugs cost three to four times more ... Read Answer >>
  2. What are the differences between brand name drugs and generic drugs?

    Discover the process by which brand name drugs lose their patent, allowing generics to be manufactured, as well as the differences ... Read Answer >>
  3. What is the drugs sector?

    Learn more about the drug industry and how new drugs are brought to market. Find out about how drug research is financed ... Read Answer >>
  4. What process does a company need to follow to bring a new drug to market?

    Learn about the costly price of bringing new drugs to market. Discover why the pharmaceutical industry invests billions of ... Read Answer >>
  5. Do financial advisors get drug tested?

    Learn how financial advisor regulatory bodies do not require drug testing but many individual firms that hire advisors do ... Read Answer >>
  6. How does the strength of the IPO market affect the drugs sector?

    Discover how the strength of the IPO market affects the drugs sector. A strong IPO market reflects healthy risk appetites ... Read Answer >>
Hot Definitions
  1. Debt/Equity Ratio

    The D/E ratio indicates how much debt a company is using to finance its assets relative to the value of shareholders’ equity.
  2. Exchange-Traded Fund (ETF)

    A security that tracks an index, a commodity or a basket of assets like an index fund, but trades like a stock on an exchange.
  3. Net Present Value - NPV

    Net Present Value (NPV) is the difference between the present value of cash inflows and the present value of cash outflows ...
  4. Return On Equity - ROE

    The amount of net income returned as a percentage of shareholders equity. Return on equity measures a corporation's profitability ...
  5. Bond

    A bond is a fixed income investment in which an investor loans money to an entity (corporate or governmental) that borrows ...
  6. Whole Life Insurance Policy

    A life insurance contract with level premiums that has both an insurance and an investment component. The insurance component ...
Trading Center