A novel formulary

Anatomical, Therapeutic, Chemical system

The ATC system was developed in Scandinavia for the study of pharmacoepidemiology. The system was adopted by the World Health Organization Pharmacoepidemiology Program and was subsequently introduced in Canada as a mechanism to facilitate therapeutic comparisons by the federal Patented Medicines Price Review Board. Two aspects of the ATC system are particularly appealing: the fact that prescribing is directed by disease within particular anatomic systems rather than classifications based on pharmacologic actions, and the proven value of the system in pharmacoepidemiologic research.

The ATC system has a branching logic that is intuitive with the therapeutic process. It begins with the anatomic system within which the disease or symptom occurs (e.g., cardiovascular system, angina pectoris), moves into the broad therapeutic category (antianginal) and, finally, provides specific chemical products that are of proven value in this setting (nitrates, beta-blockers and calcium-channel blockers). In this example, the final category (level 5) is the specific nitrate, beta-blocker or calcium-channel blocker that the physician may wish to prescribe.

Comprehensive listing of drugs

A comprehensive listing of drugs was decided on rather than an exclusive listing of drugs reimbursed under the program. An example of a listing is provided to assist the reader with the formulary layout (Figure 1).

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Figure 1. Example of a listing in the Nova Scotia formulary. 1 = therapeutic main group; 2 = therapeutic subgroup; 3 = chemical/therapeutic subgroup; 4 = subgroup for chemical substance; 5 = brand or manufacturer's name of the drug, including dosage form, or route and strength, or both; 6 = recommendation on use; 7 = relative cost; 8 = benefit status (plans for which the drug is a benefit); 9 = drug identification number; 10 = manufacturer code; 11 = interchangeable drug group box; 12 = interchangeable drug heading; and 13 = maximum allowable cost applies (if this column is blank, there is no maximum allowable cost).

Recommendation on use (colour coding)

To assist physicians in selecting the most appropriate therapy, a recommendation on use has been assigned to each product in a category. Therapeutic considerations, based on the recommendations in the treatment summaries rather than on costs, are the basis for classification as green, number or red. Older, established medications coded green or amber should not be abandoned for newer medications coded green or amber unless efficacy is substantially improved, toxicity is reduced, or cost-effectiveness is enhanced.

Green: These drugs are, for most indications, the first-line choice for treatment based on efficacy, safety and clinical experience.

Amber: These drugs are, for most indications, the second-line choice for treatment based on efficacy, safety and clinical experience.

Red: These drugs are, for most indications, the third-line choice for treatment based on efficacy, safety and clinical experience. Medications coded as red may require special expertise to determine use or to monitor therapy because of high risk of adverse effects or toxicity, or may be inappropriate compared with other agents that have similar therapeutic effects. As well, all drugs for intravenous use have been listed as red because they are generally administered in the hospital setting or at home by specially trained professionals.

In general, drugs designated as green or amber can be considered appropriate for physicians with general knowledge or experience of their use. Drugs designated as red should be used only be physicians with special expertise, and in many cases they require special written authorization. It was appreciated that this colour coding is somewhat arbitrary and that revision will likely be necessary as new information becomes available on the therapeutic value and relative toxicity of specific products.

Given a choice within a particular therapeutic category, and given a variety of options within a specific recommendation on use, whether it be green, amber or red, it is hoped that the physician will choose the least expensive product of those appropriate to treat a given patient. If the physician chooses a drug other than one designated green in the least expensive category, it is expected that she or he will be able to provide reasonable justification to the patient, the insurance company or the government payer for selecting an alternative product. Usual reasons are likely to be categorized as absolute (or relative) contraindication, development of a troublesome or serious adverse event, or failure to respond appropriately to a reasonable dosage and duration of treatment.

Relative cost (within each therapeutic grouping)

Drug within categories are compared in relation to the unit cost, daily cost and, in some instances, treatment costs. They are assigned 1, 2 or 3 dollar signs. Those coded $ are the least expensive, those coded $$ are moderately expensive, and those coded $$$ are the most expensive relative to other treatments used for similar therapeutic indications.

Interchangeable drugs

The formulary indicates drugs that have been deemed interchangeable by the Drugs and Therapeutics Committee of the Nova Scotia Department of Health.

Drugs with maximum allowable cost

For genetic drugs that meet the criteria for interchangeability, the Seniors and Family Benefits Pharmacare programs implemented the MAC program. This program sets a maximum allowable cost (MAC) for each interchangeable category with benefit status, based on the lowest-priced brand within that category. The additional cost of a higher-priced brand (usually the brand-name product) is paid by the patient. In the case of a documented adverse reaction to a particular brand, exceptions can be made to cover the cost of a more expensive drug.

"Special MACs" have been assigned to products relative to others within the same therapeutic classification. For example, the special MAC for the H_2-receptor antagonists famotidine (Pepcid) and nizatidine (Axid) corresponds to an equivalent dose of ranitidine (Zantac). Again, the patient is required to pay the difference when a more expensive product is prescribed, unless the need for an exception is defined.

Drugs approved for reimbursement

Drugs are approved for reimbursement under 2 programs, of which the Seniors' program is the largest, accounting for 80% of the government's expenditure on Pharmacare. The benefit status of medications reimbursed under these programs is indicated by the letter S (Seniors' Pharmacare), F (Family Benefits and Income Assistance), D (Diabetic Assistance) or E (exception status drug). If this column is blank, the product is not a benefit under any of these programs.

Drug identification number and manufacturer

In keeping with standard formulary practice, the drug identification number and the standard manufacturer code are listed for each product.

Treatment summaries

Treatment summaries are brief overviews of therapeutic advice for prescribers. They are written by experts, edited and revised in collaboration with pharmacists who have special expertise in drug information, and updated as important new information on disease management is introduced. Relevant nonpharmacologic management is emphasized, in addition to a recommended approach to disease or symptom management with medications.

Format and updating

The formulary is presented in a loose-leaf binder in which drugs are divided by ATC classification. There are 2 indices. An alphabetical listing of drugs (both proprietary and nonproprietary names) directs the prescriber to the relevant ATC section. An alphabetical listing of treatment summaries is cross-referenced with the relevant ATC section. Routine updates for the formulary are provided at least every 6 months. Amendments include the addition of new drugs, additions to the lists of approved interchangeable products, deletions, alterations to colour coding, and new or modified treatment summaries. An electronic format of the formulary is being developed and will be made available to prescribers.