TA的每日心情 |
2020-7-28 15:34 |
|---|
|
这是WHO上有关药物利用研究的介绍，具体网址是http://www.whocc.no/atcddd/atcsystem.html#6
About the ATC/DDD system
History of the ATC/DDD system
The field of drug utilization research has attracted increasing interest since its infancy in the 1960s. At a symposium in Oslo in 1969 entitled The Consumption of Drugs, it was agreed that an internationally accepted classification system for drug consumption studies was needed. At the same symposium the Drug Utilization Research Group (DURG) was established and tasked with the development of internationally applicable methods for drug utilization research.
By modifying and extending the European Pharmaceutical Market Research Association (EPhMRA) classification system, Norwegian researchers developed a system known as the Anatomical Therapeutic Chemical (ATC) classification.
In order to measure drug use, it is important to have both a classification system and a unit of measurement. To deal with the objections against traditional units of measurement, a technical unit of measurement called the Defined Daily Dose (DDD) to be used in drug utilisation studies was developed.
The Nordic Council on Medicines (NLN) established in 1975, collaborated with Norwegian researdhers to further develop the ATC/DDD system. The NLN published the Nordic Statistics on Medicines using the ATC/DDD methodology for the first time in 1976. Since then the interest in the ATC/DDD system for drug utilisation research has expanded.
In 1981, the WHO Regional Office for Europe recommended the ATC/DDD system for international drug utilization studies. In connection with this, and to make the methodology more widely used, there was a need for a central body responsible for co-ordinating the use of the methodology. The WHO Collaborating Centre for Drug Statistics Methodology was accordingly established in Oslo in 1982. The Centre is now located at the Norwegian Institute of Public Health. The Norwegian government funds the Centre.
In 1996, WHO recognised the need to develop use of the ATC/DDD system as an international standard for drug utilization studies. The Centre was therefore linked directly to WHO Headquarters in Geneva instead of the WHO Regional Office for Europe in Copenhagen. This was seen as important to allow close integration of international drug utilization studies and WHO抯 initiatives to achieve universal access to needed drugs and rational use of drugs particularly in developing countries. Access to standardised and validated information on drug use is essential to allow audit of patterns of drug utilization, identification of problems, educational or other interventions and monitoring of the outcomes of the interventions.
When the decision on globalizing the ATC/DDD system was taken, the WHO Division of Drug Management and Policies established the WHO International Working Group for Drug Statistics Methodology. The WHO Collaborating Centre for Drug Statistics Methodology receives expert advice from the Working Group.
The purpose of the ATC/DDD system
The purpose of the ATC/DDD system is to serve as a tool for drug utilization research in order to improve quality of drug use. One component of this is the presentation and comparison of drug consumption statistics at international and other levels.
A major aim of the Centre and Working Group is to maintain stable ATC codes and DDDs over time to allow trends in drug consumption to be studied without the complication of frequent changes to the system. There is a strong reluctance to make changes to classifications or DDDs where such changes are requested for reasons not directly related to drug consumption studies. For this reason the ATC/DDD system by itself is not suitable for guiding decisions about reimbursement, pricing and therapeutic substitution.
The classification of a substance in the ATC/DDD system is not a recommendation for use, nor does it imply any judgements about efficacy or relative efficacy of drugs and groups of drugs.
The ATC classification ?structure and principles
Structure
In the Anatomical Therapeutic Chemical (ATC) classification system, the drugs are divided into different groups according to the organ or system on which they act and their chemical, pharmacological and therapeutic properties.
Drugs are classified in groups at five different levels. The drugs are divided into fourteen main groups (1st level), with one pharmacological/therapeutic subgroup (2nd level). The 3rd and 4th levels are chemical/pharmacological/therapeutic subgroups and the 5th level is the chemical substance. The 2nd, 3rd and 4th levels are often used to identify pharmacological subgroups when that is considered more appropriate than therapeutic or chemical subgroups.
The complete classification of metformin illustrates the structure of the code:
A Alimentary tract and metabolism
(1st level, anatomical main group)
A10 Drugs used in diabetes
(2nd level, therapeutic subgroup)
A10B Blood glucose lowering drugs, excl. insulins
(3rd level, pharmacological subgroup)
A10BA Biguanides
(4th level, chemical subgroup)
A10BA02 Metformin
(5th level, chemical substance)
Thus, in the ATC system all plain metformin preparations are given the code A10BA02.
Nomenclature
International non-proprietary names (INN) are preferred. If INN names are not assigned, USAN (United States Adopted Name) or BAN (British Approved Name) names are usually chosen.
WHO抯 list of drug terms is used when naming the different ATC levels.
Inclusion and exclusion criteria
The WHO Collaborating Centre in Oslo establishes new entries in the ATC classification on requests from the users of the system. These include manufacturers, regulatory agencies and researchers. The coverage of the system is not comprehensive. A major reason why a substance is not included is that no request has been received.
The Centre gives priority to preparations containing well-defined substances which have an INN name and which are:
New chemical entities and biologicals proposed for licensing in a range of countries.
Existing well-defined substances used in a variety of countries.
Other medicines are considered on a case by case basis.
A new medicinal substance is normally not included in the ATC system before an application for marketing authorisation is submitted in at least one country. Complementary and traditional medicinal products are in general not included in the ATC system.
Principles for classification
Medicinal products are classified according to the main therapeutic use of the main active ingredient, on the basic principle of only one ATC code for each pharmaceutical formulation (i.e. similar ingredients, strength and pharmaceutical form).
A medicinal product can be given more than one ATC code if it is available in two or more strengths or formulations with clearly different therapeutic uses.
A medicinal product may be used for two or more equally important indications, and the main therapeutic use of a drug may differ from one country to another. This will often give several classification alternatives. Such drugs are usually only given one code, the main indication being decided on the basis of the available literature. Problems are discussed in the WHO International Working Group for Drug Statistics Methodology where the final classification is decided. Cross-references will be given in the guidelines to indicate the various uses of such drugs.
The ATC system is not strictly a therapeutic classification system. At all ATC levels, ATC codes can be assigned according to the pharmacology of the product. Subdivision on the mechanism of action will, however, often be rather broad, since a too detailed classification according to mode of action often will result in having one substance per subgroup which as far as possible is avoided. Some ATC groups are subdivided in both chemical and pharmacological groups. If a new substance fits in both a chemical and pharmacological 4th level, the pharmacological group should normally be chosen.
Substances classified in the same ATC 4th level cannot be considered pharmacotherapeutically equivalent since their mode of action, therapeutic effect, drug interactions and adverse drug reaction profile may differ.
Principles for changes to ATC Classification
As the drugs available and their uses are continually changing and expanding, regular revisions of the ATC system will always be necessary.
Changes in the ATC classification should be kept to a minimum. Before alterations are made, difficulties arising for the users of the ATC system are considered and related to the benefits achieved by the alteration.
Alterations in ATC classification are made when the main use of a drug has clearly changed, and when new groups are required to accommodate new substances or to achieve better specificity in the groupings.
When an ATC code is altered, the DDD is also reviewed.
Other ATC classification systems
ATCvet classification
The Anatomical Therapeutic Chemical classification for veterinary medicinal products, ATCvet, is based on the same main principles as the ATC system for medicines for human use. A medicinal substance used in both human and veterinary medicine will be classified in a way that makes it easy to recognise that it is the same substance. The ATCvet classification was developed by the Nordic Council on Medicines, and is now run by the WHO Collaborating Centre in Oslo. Further information about the ATCvet classification can be obtained on our website www.whocc.no/atcvet or received from the Centre in Oslo using the same address as for the ATC/DDD system or by e-mail: whocc@fhi.no
ATC herbal classification
A framework for ATC classification of herbal remedies has been developed by Dr. Peter de Smet, The Netherlands. The Uppsala Monitoring Centre has published Draft Guideilnes for Herbal ATC (HATC) classification and a Draft Herbal ATC Index. Further information about the Herbal ATC classification can be obtained from Dr. Mohamed Farah [address: the Uppsala Monitoring Centre (WHO Collaborating Centre for International Drug Monitoring), Stora Torget 3, S-753 20 Uppsala, Sweden, E-mail: mohamed.farah@who-umc.org
Other classification systems
The ATC classification system was originally based on the same main principles as the Anatomical Classification (AC-system) developed by the European Pharmaceutical Market Research Association (EPhMRA) and the Pharmaceutical Business Intelligence and Research Group (PBIRG).
In the EPhMRA system drugs are classified in groups at three or four different levels. The ATC classification system is modified and extended from the EPhMRA system by the addition of a therapeutic/pharmacological/chemical subgroup as the fourth level and a chemical substance subgroup as the fifth level.
Since 1991 there has been a consultation between the EPhMRA classification committee and the WHO Collaborating Centre for Drug Statistics Methodology in order to achieve a better harmonisation between the two systems. It should be emphasised that there are many differences between the EPhMRA classification and the ATC classification. This means that data prepared using the ATC classification cannot be directly compared with data prepared using the EPhMRA system. The abbreviation ATC is unfortunately also used for the EPhMRA classification, which can cause confusion.
The EPhMRA classification system is used world-wide by IMS (Intercontinental Medical Statistics) in producing marketing research statistics for the pharmaceutical industry.
The DDD ?definition and principles
The basic definition of the unit is:
The DDD is the assumed average maintenance dose per day for a drug used for its main indication in adults.
A DDD will only be assigned for drugs that already have an ATC code.
It should be emphasised that the defined daily dose is a unit of measurement and does not necessarily reflect the recommended or prescribed daily dose. Doses for individual patients and patient groups will often differ from the DDD and will necessarily have to be based on individual characteristics (e.g. age and weight) and pharmacokinetic considerations.
Drug consumption data presented in DDDs only give a rough estimate of consumption and not an exact picture of actual use. DDDs provide a fixed unit of measurement independent of price and formulation enabling the researcher to assess trends in drug consumption and to perform comparisons between population groups.
DDDs are not established for topical preparations, sera, vaccines, antineoplastic agents, allergen extracts, general and local anesthetics and contrast media.
Principles for DDD assignment
DDDs for plain substances are normally based on monotherapy. Exceptions to this rule are given in the guidelines.
A DDD will normally not be assigned for a substance before a product is approved and marketed in at least one country.
The assigned DDD is based on the following principles:
The average adult dose used for the main indication as reflected by the ATC code. When the recommended dose refers to body weight, an adult is considered to be a person of 70 kg. It should be emphasised that even special pharmaceutical forms mainly intended for children (e.g. mixtures, suppositories) are assigned the DDD used for adults. Exceptions are made for some preparations mainly used by children, e.g. growth hormones and fluoride tablets.
The maintenance dose is usually preferred when establishing the DDD. Some drugs are used in different initial doses but this is not reflected in the DDD.
The treatment dose is generally used. If, however, prophylaxis is the main indication, this dose is used, e.g. for fluoride tablets (A01AA01) and some antimalarials.
A DDD is usually established according to the declared content (strength) of the product. Various salts of a substance are usually not given different DDDs. Exceptions are described in the guidelines for the different ATC groups.
The DDD is nearly always a compromise based on a review of the available information including doses used in various countries when this information is available. The DDD is sometimes a dose that is rarely if ever prescribed, because it is an average of two or more commonly used dose sizes.
Combination products
The DDDs assigned for combination products are based on the main principle of counting the combination as one daily dose, regardless of the number of active ingredients included in the combination. If a treatment schedule for a patient includes e.g. two single ingredient products, then the consumption will be measured by counting the DDDs of each single ingredient product separately. If , however, a treatment schedule includes a combination product containing two active ingredients, then the calculated consumption measured in DDDs will normally be lower since the DDD for the combination will be counted.
Example I:
Treatment with two products, each containing one active ingredient:
Product A: Tablets containing 20 mg of substance X (DDD = 20 mg)
Product B: Tablets containing 25 mg of substance Y (DDD = 25 mg)
The dosing schedule 1 tablet of A plus 1 tablet of B daily will be calculated as a consumption of 2 DDDs.
Example II:
Treatment with a combination product containing two active ingredients:
Products C: Tablets containing 20 mg of substance X and 12.5 mg of substance Y. The DDD of the combination products is assigned as 1 UD = 1 tablet.
The dosing schedule 1 tablet of C daily will be calculated as 1 DDD (even though it will be equivalent to 1.5 DDD of the single active ingredients).
The following principles for assigning DDDs to combination products apply:
For combination products (other than the combination products used in hypertension, see point 2 below) where the ATC code identifies the main ingredient (i.e. for the 50- and 70-series combinations and for some 4th levels combinations), the DDD for the combination product should be equal to the DDD for the main active ingredient.
For combination products used for treatment of hypertension (i.e. ATC group C02L, C02N, C03E, C07b-f, C08 and C09), DDDs are based on the average number of dosing intervals per day. This means that: 1 tablet is the DDD for combinations given once daily, whereas 2 tablets is the DDD for combinations given twice daily and 3 tablets is the DDD for combinations given three times daily etc. This principle means that the assigned DDDs may differ from the DDD assigned for the main active ingredient (according to ATC code).
In some ATC groups, it has been decided to use fixed DDDs for all combination products given in e.g. number of tablets regardless of strength. These rules are clearly stated in the chapters of each ATC main group in this publication (e.g. ATC group A02AD, A02BD and A02BX).
For all combination products where a DDD assigned deviates from the two rules given above, a list of these DDDs are available from the Centre and on this website (DDD combi).
Principles for reviewing and changing DDDs
As the dosages used may change over time, it will always be necessary to make some alterations.
The International Working Group for Drug Statistics Methodolgoy may review a DDD whenever the Group finds it appropriate.
Changes of DDDs should be kept to a minimum and avoided as far as possible. Too many alterations will always be disadvantageous for long-term studies on drug utilization. Before alterations are made, difficulties arising for the users are weighed against the benefits achieved by the alteration.
The same principles used to assign new DDDs also apply when DDDs are reviewed.
Changes are generally not made unless they are at least of the order of 50%. This rule is not used for the three-year revision of DDDs, where smaller alterations are allowed. Further, minor alterations are allowed for important drugs, which are frequently used.
DDD review after three years
All newly assigned DDDs are reviewed during the third year after inclusion in the ATC index with DDDs.
The DDDs are reviewed at the first semi-annual meeting of the WHO International Working Group for Drug Statistics Methodology.
Further reviews of DDDs
After the first three years period, the DDD normally remains unchanged for at least five years unless the WHO Working Group decides to make a total revision of all DDDs assigned in an ATC group.
Proposed changes in DDDs based on new information will always be considered, but only after the three years revision has been performed.
Last updated: 2008-08-14 |
|
[复制链接]
/1 
鲁公网安备 37020202001532号 
IP卡
狗仔卡
提升卡
置顶卡
沉默卡
喧嚣卡
变色卡
抢沙发
千斤顶
显身卡
