Barcoding the NDC
The National Drug Code (NDC)
The NDC is a unique 10-digit, 3-segment number assigned to each medication listed under Section 510 of the U.S. Federal Food, Drug, and Cosmetic Act. The number identifies the labeler or vendor, product, and trade package size:
The product and package codes are assigned by the firm.
According to the FDA, the NDC may be in one of the following configurations: 4-4-2, 5-3-2, or 5-4-1. An asterisk may appear in either a product code or a package code. It simply acts as a place holder and indicates the configuration of the NDC.
Barcode Size and Placement
The space a barcode occupies becomes a prime concern with unit dose drug labels. A unit dose label is typically 1.75" wide and 1" tall. The label must have text containing (at least): drug name and strength, route of administration, manufacturer, lot number, and expiration date. This much text leaves quite a small area for the barcode. Because it is the most compact and accurate 1D symbology, Code 128C is usually the best choice for unit dose packages.
Another consideration when creating small barcodes is that the scanner must be able to dependably read them. Barcode scanners may read different symbologies more reliably at different sizes. For example, the Symbol Laser barcode scanner dependably reads the Code 39 when printed as small as 6 points, but only reads the Code 128 barcode when printed at 8 points. Whereas the IDAutomation Plug 'n Play USB barcode scanner reads both Code 128 and Code 39 at 6 points and above.
Barcode length and height
Optimizing the length of the barcode is important when 1D barcode readers are used. Common laser scanners must detect the entire barcode at once in order to read it. The longer the barcode is, the greater distance the scanner must be held away from the barcode, making it difficult or impossible to read. Code 128C (double density numeric) is able to produce a barcode that is both compact enough to fit on a unit dose label and able to be scanned accurately.
The height of the barcode must also be considered. Optimally, the height must be 15% of the length or 0.25” which ever is greater.
Barcode Quiet Zones
Another important consideration is the Quiet Zone (QZ).
The QZ is the area around the bar code that must be kept clear of text.
Bar code scanners depend on the QZ to help identify the bar code. The lack of an adequate QZ can cause the bar code scanner to confuse the bar codes with text or graphics resulting in the scanner ignoring a valid symbol. Each symbology has a different QZ size requirement, however all quiet zones are based on the size of the Narrow Bar Width (NBW) for 1D bar codes and Module (MDL) for 2D bar codes.
The final consideration for unit dose labels is barcode placement. Specifically, the barcode must not be printed too close to the edges of the label. Allow edge space per the QZ requirements listed above.
Code 128 Technical Information
Code 128 is a continuous, variable-length, high-density symbology which permits the encoding of alphanumeric data. The symbology encodes the full ASCII 128 character set, and includes a checksum digit for verification. Code 128 has been widely implemented in many applications where a relatively large amount of data must be encoded in a relatively small amount of space. It is the most accurate 1D (linear) barcode type.
Every Code 128 character has 3 bars and 3 spaces comprising a total of 11 modules. Each bar or space can be one, two, three, or four modules wide. The Code 128 specification defines three character subsets or modes:
Because 128C allows numeric data to be encoded at double density, it is the best choice for unit dose labels.
Data Matrix Technical Information
Data Matrix symbols are rectangular, usually square in shape and composed of square "cells" which represent bits. Depending on the coding used, a "light" cell represents a 0 and a "dark" cell is a 1.
Every Data Matrix is composed of two solid adjacent borders in an "L" shape (called the "finder pattern") and two other borders consisting of alternating dark and light "cells" or modules (called the "timing pattern"). Within these borders are rows and columns of cells encoding information.
The finder pattern is used to locate and orient the symbol while the timing pattern provides a count of the number of rows and columns in the symbol. As more data is encoded in the symbol, the number of cells (rows and columns) increases.
A Data Matrix symbol can store up to 2,335 alphanumeric characters. The information encoded can be text and/or numeric data. Error correction codes are often used to increase reliability. Data Matrix is one of the most accurate barcode symbologies. Even if one or more cells are damaged, the message can still be read.
The most popular application for Data Matrix is marking small items, due to the code's ability to encode fifty characters in a symbol that is readable at 2 or 3 mm2 and the fact that the code can be read with only a 20% contrast ratio. A Data Matrix is scalable; commercial applications exist with images as small as 300 micrometres (laser etched on a 600 micrometre silicon device) and as large as a 1 metre (3 ft) square (painted on the roof of a boxcar).
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