Drug Strength

Each drug product is defined by its ingredient(s), strength and drug form. E.g., Acetaminophen 250 mg Oral Tablet (Standard Vocabulary concept 19107242) contains the ingredient Acetaminophen at a strength of 250 mg, and is formulated as an oral tablet.

In the OMOP Standard Vocabulary, you can query the ingredient and the form for each drug product. Use the Standard Vocabulary Queries if you need help how to do it. However, the strength is not prorvided by RxNorm and not part of the Standard Vocabulary.

We therefore created an additional supplemental table DRUG_STRENGTH. It is included in the distribution file of the OMOP Standard Vocabulary. It defines, where possible, for a drug product the strength for each ingredient:

Column Name Description
DRUG_ID contains the CONCEPT_ID of the drug, e.g. 19107242 for "Acetaminophen 250 mg Oral Tablet".
INGREDIENT_ID contains the CONCEPT_ID of the ingredient, e.g. 1125315 for "Acetaminophen". Multi-ingredient drugs will have one record per ingredient while listing the same DRUG_ID.
AMOUNT_VALUE contains the numerical value of the drug strength, e.g. "250".
AMOUNT_UNIT contains the unit of the drug strength, e.g. "mg".
CONCENTRATION_VALUE contains the numerical value of the drug concentration. For example, in the drug 1126750 "Acetaminophen 100 MG/ML Oral Solution" this would be "100".
CONCENTRATION_ENUM_UNIT contains the enumerator part of the unit, e.g. "mg".
CONCENTRATION_DENOM_UNIT contains the denominator part of the unit, e.g. "ml".
VALID_START_DATE contains the date at which the strength assignment started to be valid. A date of "1-Jan-1970" stands for always active.
VALID_END_DATE contains the date at which the strength assignment ended to be valid. A date of "31-Dec-2099" stands for currently active.
INVALID_REASON contains a flag on validity: active records are null and deprecated are "D".

The DRUG_STRENGTH table can be used in connection with the DRUG_EXPOSURE table of the OMOP Common Data Model. To calculate the dose of active ingredient a patient is exposed to join it with the DRUG_STRENGTH table using the drug_id. In future, this page will contain details of how to do this, how to avoid artifacts of dirty data, how to create "dose ranges" as well as "dose eras" and how to use them in analytical methods.

Additional details about this table:

  1. The table was built using RxNorm Drug Components. These are Ingredient-Strength combinations (e.g. Acetaminophen 250 MG). For details, download the source code for building DRUG_STRENGTH.
  2. If you only want to use this table for drug and ingredient concepts that are valid (where the field INVALID_REASON is null), the DRUG_STRENGTH records can be used as such. If you want to use deprecated concepts read on:
  3. Records in the DRUG_STRENGTH table have a lifecycle definition that is equivalent to other tables of the vocabulary. Their validity changes over time and is defined by the corresponding Drug Component records (not listed in DRUG_STRENGTH). Records are valid in the time interval between VALID_START_DATE and VALID_END_DATE. Deprecated records are marked as 'D' in the INVALID_REASON field. For example, the drug concept 40003400 Acamprosate calcium 333 MG Enteric Coated Capsule, which contains 333 mg of Acamprosate, has 3 records:
  4. DRUG_ID INGREDIENT_ID AMOUNT_VALUE AMOUNT_UNIT C_VALUE C_ENUM_UNIT C_DENOM_UNIT VALID_START_DATE VALID_END_DATE INVALID_REASON
    40003400 19016390 333 mg 01-JAN-70 0-JUL-06 D
    40003400 19016390 333 mg 01-JAN-70 0-JUL-06 D
    40003400 19043959 300 mg 26-FEB-06 05-APR-09 D

    The first period defined two ingredients: 19016390 Acamprosate calcium and 19043959 acamprosate, both at 333 mg. These ingredients are synonymous, and the mistake was fixed in 2006 so that 19043959 acamprosate was assigned as the sole ingredient, albeit with a wrong strength of 300 mg. Everything was fixed in 2009, including a new drug concept (19043981 Acamprosate calcium 333 MG Enteric Coated Tablet). Bottom line: If you want to use this table to join existing concept IDs in the data you have to pick records based on the right validity time.

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drug_strength_V1_sql.zip2.42 KB