Rational prescribing

Prescribing, which is based on the four important factors of efficacy, safety, patient acceptability and cost, should be rational (see Ch. 20). While many drugs may be available to treat any particular condition, the process of selecting the most appropriate one for any individual patient should take account of all these factors, plus other patient factors, such as concurrent diseases, drugs, previous exposure and outcomes. The four factors can also be applied to selection of drugs to treat populations of patients and it is for this situation that formularies are developed. Providing drug selection is based on good quality evidence of efficacy, toxicity and cost-effectiveness, formularies then assist in making decisions regarding individual patients.

Cost-effective prescribing

Formularies often provide information on the cost of products to help users to become cost conscious. Local formularies usually include only a small proportion of the drugs listed in an extensive national formulary, such as the BNF. In general, only between 300 and 500 drugs are required to manage the majority of common conditions. If prescribers only use the drugs included in a local formulary, the range stocked by pharmacies can decrease, which reduces unnecessary outlay. Using a restricted range of drugs may allow pharmacists to buy these in bulk, further reducing costs. Formularies also encourage generic prescribing which may reduce costs even further. If fewer products are stocked, monitoring of expiry dates becomes easier and cash flow may improve. Any money saved by using a formulary may be used to benefit patients in other ways. For example, reducing the prescribing of drugs which have little evidence of therapeutic benefit, such as peripheral vasodilators, could enable more to be spent on lipid-lowering drugs. Formularies usually recommend using the most cost-effective option where there are a number of alternatives. In addition, as safety is also a key factor in drug selection, formularies may contribute to reducing the incidence of ADRs, which often carry a high cost.

Educational value

Compilation of a formulary involves researching the literature to gather evidence of efficacy and toxicity. This is highly demanding, but is of considerable educational benefit to those compiling the formulary. Formulary users also benefit. If prescribers use a restricted range of drugs frequently, they should know more about those drugs and their formulations. Ultimately, this should result in benefits for the patient, as prescribers’ greater knowledge should reduce the risk of inappropriate prescribing and hence reduces the potential for adverse effects, interactions or lack of efficacy.

Continuous care

A joint local formulary covering both primary and secondary care encourages the same range of drugs to be prescribed, which makes continuing drug treatment across the interface easier. If patient packs are dispensed, patients are more likely to use their own medicines during a hospital stay. A joint formulary also helps, as there is less chance of drug therapy having to change to comply with a different formulary on admission to hospital.

Content

The formulary should start with an introduction, giving the names of those who have compiled it, stating who is expected to use it and explaining its format. An example is shown in Figure 23.1A, from the NHS Tayside Area Formulary. It is important to state whether all the drugs included are recommended for all users, and if not, how different recommendations can be distinguished. The BNF, for example, lists drugs the Joint Formulary Committee considers less suitable for prescribing, in small type. The examples in Figures 23.1 and 23.2 illustrate how the recommended first choice drugs are highlighted. Local formularies may choose to place restrictions on some drugs, for use by specialists only, for certain indications only or in certain locations only. These drugs should also be easily distinguishable from the others in the formulary; in Figure 23.1A, these are in italic. A list of contents and an index should be included to make the formulary easy to use.

Most UK formularies follow the BNF to classify medicines and may be designed to be used in conjunction with it. Users can be directed to the monographs there for information on dosage, indications, side-effects, contraindications and precautions. Some formularies include all this information, but only for the recommended drugs. Other important information which may be given in a local formulary is local drug costs and the reasons behind the selection.

Drug costs are one of the factors taken into account when compiling a formulary (see below). The price of a drug can be expressed in several different ways. While the easiest may be the price of different pack sizes, the cost of a period of treatment may be more useful if pack sizes of similar products differ and comparisons are being encouraged. A suitable period may be 1 day, 1 month (28 days) or a standard course of treatment (e.g. 5 days for antibiotics). Since the price of the drug usually varies with the pack size, this may not be as easy to calculate as it first appears. A further complicating factor is that prices may differ in hospital and community. If a formulary is designed to be used in hospital only, the hospital price may seem most relevant. However, patients may take the drug while living in the community for much longer than they take it in hospital. Therefore the price in primary care is also of relevance, especially in joint formularies.

When large numbers of prescribers are to use a formulary, it is unlikely that they will all have been consulted about its content. If that is the case, providing explanations of how drugs were selected for the formulary is of particular importance. Many formularies state the general basis of drug selection as being efficacy, safety, patient acceptability and cost, but sometimes additional information is given. The BNF gives this type of information in introductory paragraphs to each section. An example is the statement that ‘other thiazide diuretics do not offer any significant advantage over bendroflumethiazide and chlortalidone’. It may be desirable to reference the formulary to give readers the opportunity to see the evidence on which statements such as these are based. It may also be useful to explain local preferences, particularly in the case of antibiotic selection, which should take local microbiological sensitivities into account.

Some or all of the formulary may be presented as prescribing policies or guidelines. If this approach is taken, details of which drugs are to be used in specific medical conditions should be given. It may be necessary to include alternatives and the particular occasions when they should be used. In a prescribing policy, details of the recommended dosage, route and method of administration and duration of therapy should also be included. The BNF includes a number of examples, such as a summary of antibacterial therapy for specific conditions, detailed guidance on the management of chronic and acute asthma (taken from the SIGN/BTS guideline) and extracts from NICE guidelines throughout.

A local formulary may have sections relating to prescribing in certain types of patients, such as the elderly, children, those with renal or hepatic impairment, or in pregnancy and breast-feeding. As there is little point in reproducing the BNF, these too should reflect local recommendations.

Presentation of a formulary

The appearance of a formulary is an indicator of the importance attached to it by those who have produced it. Poor presentation may result in those who are expected to use it having little respect for its contents, which may lead to poor adherence to its recommendations. It is therefore worth creating a document which is attractive and looks professional. It is also important to consider whether a paper or electronic format is desirable or whether both should be available.

Paper formats can be portable, making for ease of use in any clinical setting, from the hospital bedside to the patient’s home. However, they are expensive to produce and still require regular updating. The size of the document is an important consideration. Ideally, it should be no bigger than pocket-sized, perhaps compatible in size with the BNF, to make it easy to use the two together. A simple list of formulary drugs is a useful option, such as that illustrated in Figure 23.1B, produced by NHS Tayside ADTC. This can be supplemented by a larger document in either paper or electronic form. If the formulary is only available as a large paper document which cannot be carried around, it is much less likely to be available when needed, which may mean its recommendations are ignored. Colour and a durable cover to withstand regular use can both add further to the appearance of a paper formulary, but also increase its cost.

Electronic formats are increasingly popular, but not all professionals use a computer when prescribing, so it may still be necessary to produce a paper version, even if this is only the list of drugs. A CD version is one option, but like a paper document, requires re-distribution whenever it is updated. Other options are to publish the formulary on a local intranet or to make it available as a locally downloadable application for smart phones. Linking the local formulary to electronic prescribing systems is perhaps the ideal option. Some prescribing systems incorporate decision support tools, which can include the formulary. Electronic versions may also make it easier to evaluate the formulary by examining prescribing adherence.

Ensuring that the formulary is up-to-date is extremely important and its presentation must allow for this. Loose-leaf binding will enable easy updating, but relies on everyone modifying their own copy. It is much easier to update an electronic version which is distributed via the Internet or intranet.

Whatever format is used, the formulary should be easy to use, to encourage prescribers to refer to it when necessary. This will be helped by a contents list, which for a paper version means the pages have to be numbered. Arranging the drugs in the same order as the BNF will also help to make the formulary easier to use, for prescribers who already use the BNF. Using different typefaces and print size can make a formulary easier to use. Highlighting the drug names can be useful, as often the name of the recommended drug may be all that someone is seeking (see Fig. 23.1B).

It may also be appropriate to provide access to the formulary for local patients. Increasingly, patients have access to clinical guidelines and are informed about what treatments are recommended for their medical problems. Providing a formulary has been developed using transparent methods and drugs selected on the basis of efficacy, safety, patient acceptability and cost, there is no reason to prevent patients from knowing of its existence. Access can be via the Internet, so need not add to publication costs.