Bioavailability - what is it? The bioavailability of medicinal substances

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2018-04-02 11:50:23

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Bioavailability is the amount of drug that reached the main place of action in the human or animal body. This term denotes the number of lost and saved of nutrients that are beneficial to the body. Thus, with a high degree of bioavailability can be judged on a small number of lost therapeutic properties of any drug.

this bioavailability

How is the figure?

The standard forms of research the bioavailability of drugs is determined by a method of measuring the drugs in the blood, that is, the amount that reached the circulatory system. With different methods of introduction it has various indicators. So, with intravenous bioavailability approaching 100 %. And if you've had oral bioavailability, the volume is significantly reduced due to incomplete absorption and disintegration of the drug into its individual components.

This term is also used in pharmacokinetics to calculate the correct dosage to be followed to the patient when different methods of administration of the drug in the body.

There are two stages of bioavailability:

  1. Absolute.
  2. Relative.

the bioavailability of drugs is a

The Notion of absolute biological availability

The Absolute bioavailability is the rate resulting from the comparative analysis of a drug's bioavailability, entered by anyone, except intravenous, method and availability of the drug, administered intravenously. It is reflected in the area under a curve "volume – time", abbreviated "SPC”. To carry out such a procedure is possible only when such conditions, as the use of various dosages of different methods of introduction into the body.

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To determine the number of absolute bioavailability, the conduct of pharmacokinetic studies, aimed at obtaining the comparative analysis of “the amount of medications in relation to time" for intravenous and other method of implementation. Thus, the absolute bioavailability of medicines - is the ACC for the altered dose, obtained in the course of dividing the PPK another method of injection and intravenously.

the bioavailability of medicinal substances

The Concept of relative biological availability

The relative bioavailability is the ACC of the drug subjected to comparison with another version of the same drug taken for a basis or introduced any other way. Foundation – intravenous route, characterized by the absolute bioavailability.

To obtain data on the number of relative bioavailability in the body are used as the indicators of the amount of drug in the circulatory system or in its excretion with urine after single or multiple applications. With the aim of obtaining a high percentage of accuracy when analyzing cross method of learning. It allows you to maximize to eliminate the difference between the results obtained in physiological and pathological conditions.

What are the methods used in determining bioavailability?

To determine the low bioavailability of the drug or high scholars, the following types of methods:

  1. Comparative analysis of the changed volume of the drug between the study and the main form of the drug in plasma or urine. Such a study allows the fullest scope to determine the absolute bioavailability.
  2. A measurement of the amount of different drugs introduced into the body in the same way. This technique allows to determine the relative bioavailability.
  3. Determination of the amount of relative bioavailability by implementing medication in different ways.
  4. Study results levels of drugs in blood or urine. Performed to determine relative bioavailability.

oral bioavailability

The Advantages of HPLC

HPLC – another method of determining the bioavailability of – chromatography with high efficiency, used if necessary, the separation of complex substances to simple. Used most frequently in the study of bioavailability, as it has the following positive qualities:

  1. No limits in terms of resistance to temperature for the studied samples thus.
  2. Gives you the possibility of working with aqueous solutions, which greatly reduces the duration of analysis and improves the stage of preparation of biological samples.
  3. No need to obtain derivatives of the studied drug.
  4. Equipment used in this method of study, has excellent performance and efficiency.

the bioavailability of the drug is

What can affect the total amount of bioavailability?

The Standard amount of drug in the body Papademos devotional by equal less than 1. However, it may be even less because of some additional nuances. Thus, factors influencing bioavailability, is:

  1. Physical properties of the drug.
  2. The Form of medication andthe duration of its effects on the body.
  3. Receiving & ndash; before or after eating.
  4. Fast cleansing of the gastrointestinal tract.
  5. Exposure to other drugs in this medication.
  6. Reaction money on some food.

Bioequivalence

Another kind is the bioavailability, bioequivalence is. Originated this concept in connection with the conduct of pharmacokinetic and bioformation studies in which it was revealed that the inequality of the therapeutic drugs containing the same substance, has a direct correlation with the difference in bioavailability.

Thus, bioequivalence – is ensure the blood and tissue of the body the same number of substances.

Main indicators bioequivalence

To determine bioequivalence in drugs are used the following indicators:

  1. Increased or most complete bioavailability of the tablets in the circulatory system. Is investigated by plotting, in which two curves represent the amount of drug introduced by various methods, and the straight line indicates the minimum amount of medication required to produce a therapeutic effect.
  2. The duration of the high content of the drug. This parameter indicates the speed of absorption and the therapeutic effects on the body. To understand the essence of this indicator on the example of hypnotic medication. A small therapeutic effect it will have in half an hour or 2 – depending on the form of preparation. Therapeutic function hypnotic will perform, depending on the shape of 5 to 8 hours. Thus, despite the similarity in their effects, one form will serve to prevent sleep disorders, and the second – with a small time of peace.
  3. Change the amount of the drug in the blood after a certain time.

Start the implementation

Before starting the preparation is on sale, you should examine the bioequivalence and bioavailability of drugs is very important. To that end the following procedure:

  1. Manufacturer submits an application to the state Pharmacological Committee of the desire to release your medication in implementation. The Agency, in turn, shall issue a permit to conduct research on bioequivalence using two samples: existing and new.
  2. The Study is carried out at normal or having any disease of the volunteers in the same dosage. Each study paid for by the manufacturer.

This procedure is Carried out in special medical institutions or laboratories involving third-party experts. The selection of candidates for research must respect the following requirements:

  1. Their total number may not be less than 12. There are times when the number of volunteers increased to 25. Mostly this happens in the case of high inter-individual variation in pharmacokinetic parameters.
  2. Age of the volunteers must be of legal age and not be above 60 years.
  3. The Weight of each person should not be less or more than 20 % from ideal weight This Sex, age, and growth.
  4. Not allowed to conduct research on people suffering from cardiovascular or chronic diseases. The exception is the group of persons which recommended the use of this drug.

bioavailability pill

How is the training of volunteers?

Before signing a consent to conduct research that determines the bioavailability of a substance, each volunteer must obtain the following set of information:

  1. The Main objective of the study.
  2. The Duration of the procedure.
  3. Basic pharmacological data on the drug.
  4. Method of administration of drugs inside.
  5. Applied dosage.
  6. The Impact of drugs on the body.
  7. Disadvantages of this drug.
  8. The Nuances of power in the research process.
  9. Terms of payment of the insurance policy.

After a volunteer signs the contract and the confidentiality agreement, the researchers performed a full medical examination. It includes:

  1. General medical examination.
  2. Analysis of blood and urine.
  3. Biochemistry of blood.
  4. Blood test for HIV, syphilis and hepatitis.
  5. Definition of pregnancy in women.

Each house is equipped with everything necessary for comfortable learning. In addition, any insurance company is an agreement about getting insurance in case of a failed experiment. Additional conditions are discussed and the amount of remuneration.

Who is allowed to research?

Work with volunteers carries out the researcher. It needs to meet the following conditions:

  1. The Researcher must have a theory and practice of all the chemical and pharmacological areas.
  2. He must have a certificate of completion.
  3. The Researcher should have a full understanding of what the bioavailability of the drug (this is important) and what kind of medicine he should study.

In addition to researcher in the group should include nurses. Their responsibilities include:

  1. Monitor the health of patients.
  2. The Implementation of the regime moments.
  3. Installation of catheters.
  4. The Withdrawal of some amount of blood for analysis from patients.

More to the group include:

  1. Analytics andtechnicians.
  2. Pharmacokinetics.
  3. Mathematics.

Report on the work carried out

At the conclusion of all the research actions of the chief doctor issued a paper that should reflect the following items:

  1. The Total plan for pharmacological studies. It must be approved by Pharmacological state Committee.
  2. All the data about volunteers. Must be specified demographic, anthropometric and clinical data. The latter indicates at the involvement of the patients.
  3. The lot Numbers and the names of the companies-manufacturers, as well as the duration of their therapeutic effects.
  4. Option of the drug and the effective dose.
  5. The Method of sampling of biological material and its pre-processing.
  6. The Sequence of presentation of Analytics with the introduction of the metrological performance and demonstration chromatogram.
  7. A Complete statement of the whole course pharmacokinetic studies and evaluation of biological equivalence. Here you specify all used in the study.
  8. The Results of detection of the amount of the drug in biological samples.
  9. The Medical records of volunteers and individual profiles.
  10. The Results of the dispersion study of the values of the pharmacokinetics used to assess the biological equivalence.

low bioavailability

The procedure for bioequivalence

A Study on the bioavailability of medicines is carried out in the same dosage on two drugs: the derived and the original. In the case of requests to study multiple drugs the study is carried out separately for each.

The time Interval between taking the generic and the original is determined by the duration of the movement of drugs in the body, the period of partial removal. It needs to be equal to an average of 6 periods of partial removal. The material used for the study, may be plasma, serum or blood. It is taken from a vein in the crook of the elbow through the catheter. The selection must be made three times:

  1. At the time of primary growth drug. Should be about 3 points on the curve "concentration - time”.
  2. At the time of high suction. Used about 5 points.
  3. At the time malabsorption. Used about 3 points.

The study can be considered acceptable if the value of the area under the curve "concentration - time” at a distance from zero to the last sample is about 80 %.


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Alin Trodden - author of the article, editor
"Hi, I'm Alin Trodden. I write texts, read books, and look for impressions. And I'm not bad at telling you about it. I am always happy to participate in interesting projects."

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