Quantifying the clinical significance of drug-drug interactions: scaling pharmacists' perceptions of a common interaction classification scheme

OBJECTIVE

To develop a precise, interval level scale of the clinical significance of drug-drug interactions that reflects the professional judgments of practicing pharmacists.

PARTICIPANTS

A convenience sample of 63 practicing pharmacists representing hospital (clinical and staff) and retail (chain and independent) practice settings.

METHOD

Pharmacists judged the similarity among 15 interaction categories that have been commonly used to classify drug-drug interactions. A multidimensional scaling technique produced a spatial representation (i.e., a psychological map) of the structure inherent in those similarity judgments. Pharmacists' ratings of clinical significance were projected onto that same spatial representation using a multiple regression procedure, and the resulting information was used to develop a scale of clinical significance.

RESULTS

The clinical significance scale developed from pharmacists' judgments was substantially different from a comparison scale published in a popular reference. The new scale was more precise than the comparison scale, and it also approximated an interval level of measurement. The judgments used to produce the new clinical significance scale were not reliably influenced by pertinent demographic characteristics of the sample.

CONCLUSIONS

Inconsistencies between published clinical significance scales and the professional judgments of practitioners could affect patient care to the degree that a summary measure of clinical significance affects a practitioner's response to a potential drug-drug interaction. The clinical significance scale developed in this study has good measurement characteristics and reflects the professional judgments of practicing pharmacists. Use of the new scale is recommended on these grounds, although further assessment of its generality is warranted.

A literature review comparing the economic, clinical, and humanistic attributes of dihydroergotamine and sumatriptan

The value of different pharmaceuticals in treating migraine is frequently based on clinical efficacy only. This article assumes a broader perspective and compares the clinical, economic, and humanistic attributes of two antimigraine medications, dihydroergotamine (DHE) and sumatriptan, based on a literature review. DHE is an established product with over 40 years of use in the treatment of migraine. Sumatriptan is a new product with a higher acquisition cost than DHE. Because sumatriptan costs more than DHE, the question must be asked. "Does sumatriptan provide advantages that offset this price differential?" This question reflects the growing concern among payers and patients over the cost and effectiveness of therapies. However, it is not easily answered. Direct comparative data are not available, and data sources are different for the two products. Moreover, the products are currently marketed in different dosage forms--intramuscular for DHE and subcutaneous for sumatriptan. The literature reviewed indicates that the clinical attributes of the two products are similar, with each having slightly different advantages and disadvantages. However, the DHE literature is generally limited to uncontrolled studies, whereas the sumatriptan literature reports the results of rigorously designed, randomized, double-blind, placebo-controlled clinical trials. Published data on the products' economic and humanistic attributes are limited. We concluded that the literature does provide important, albeit limited, data on the economic, clinical, and humanistic attributes of DHE and sumatriptan that permit restricted comparisons. The limitations of the data highlight the need for comparative studies of these products' multidimensional attributes both in controlled clinical trials and under actual practice conditions.

Economic impact of cost-containment strategies in third party programmes in the US (part I)

The rising cost of healthcare has strained the resources of governments, private third parties and individuals with responsibility to pay for it. Various strategies have been used in an attempt to control costs. This article examines the economic impact of 4 such strategies: (a) cost sharing; (b) prescription limits; (c) rebates; and (d) cost limits. Cost sharing has been successful at reducing utilisation of prescription drugs, although the effects have not been uniform across therapeutic categories. However, the long term effect on cost and utilisation of other medical services, and the impact on overall health status, remain largely unknown. Some evidence suggests that utilisation of other services may increase. The available data regarding drug rebate programmes have been descriptive in nature. However, the designs employed in this research do not establish a direct causal relationship between rebate programmes and changes in Medicaid drug expenditure. Furthermore, still unknown is the degree of cost shifting and the effect of the rebate programme on other large public and private drug purchasers. The Maximum Allowable Cost programme led to direct savings in drug costs, but the size of these savings was variable and uncertain because of administrative costs of the programme. The Estimated Acquisition Cost programme has not resulted in significant savings.