Narx Score Tutorial


Narx Scores are type-specific use indicators.

They range from 000-999.

They represent a relative scoring system of controlled substance usage.


Narx Scores exist for 3 different drug types.

  1. Narcotics
  2. Sedatives
  3. Stimulants


Narx Scores are based on the number of:

  • Providers
  • Pharmacies
  • Milligram equivalents (MME)
  • Overlapping prescriptions

Last Digit

The last digit of the Narx Score corresponds to the number of active prescriptions for that drug type.

Derivation 1

The Narx Score is derived from a population study of over 5 million patients.

In this study the number of providers, pharmacists, MME, and overlaps were determined for every patient over a 2 year period.

Derivation 2

Each measurement was converted to a scaled value between 0 and 99 allowing the population to determine the boundaries.

Derivation 3

Scaled values were created for every measurement type.

Derivation 4

This principle of establishing population based scaled values was applied to 4 different time periods (for each drug type).

Narx Score Calculation 1

The first step in calculating a Narx Score is to determine the scaled values for every time period for the patient.

Narx Score Calculation 2

The second step in the calculation is to determine the weighted average of all of the scaled values.

½ of the weighting is allocated to MME and the rest together equal ½.

Narx Score Calculation 3

The final step is to append the number of active prescriptions for that type (i.e. Narcotic).

Narx Score Summary

If we think of providers, pharmacies, and overlaps collectively as “behaviors” then three scoring patterns emerge.

Narx Score Summary

The distribution of Narx Scores in the population is such that the vast majority score low and very few score high.