DISCUSSION

According to our criteria, 54.7% of first omeprazole prescriptions for the senior population of Quebec were appropriate. This proportion is high, especially when compared with results of other studies performed in Canada or elsewhere, and more specifically with the findings of two studies performed around the same time period – one in the ambulatory setting in Ontario and one in the hospital setting in Quebec.

McBride et al studied the prevalence of appropriate omeprazole prescribing for the ambulatory senior population of Ontario from April 1992 to March 1993. They determined that only 20% of Ontario seniors received omeprazole appropriately. When their study took place, omeprazole was in the restricted formulary in Ontario. Thus, an omeprazole prescription for a recipient of the Ontario Drug Benefit program required written justification of the indication by the prescriber, plus acknowledgement of this indication by the pharmacist, before being filled. The Ontario Drug Benefit criteria permitted the prescription of omeprazole after a trial of at least four weeks of an H2RA. Concurring with Ontario’s criteria, McBride et al considered a first omeprazole prescription to be appropriate if it was not preceded by an H2RA prescription within one to six months.

In our study, we considered omeprazole prescriptions that occurred less than one month after receipt of a prescription for an H2RA to be appropriate. We used a less stringent criterion because a shorter therapeutic trial may be justified by side effects, drug interactions or other relevant clinical factors. Even so, had we defined appropriate prescribing by using the same criterion as that of McBride et al, 37.6% of omeprazole prescriptions for Quebec’s seniors would still have been classified as appropriate. Thus, the prescription of omeprazole appears to be more appropriate for Quebec seniors than for Ontario seniors, even without a limited-use program in Quebec. This unexpected difference in the appropriateness of omeprazole prescribing between the two provincial jurisdictions may indicate that restrictive policies do not always succeed in promoting the appropriate use of a drug and that many factors determine the quality of prescribing.

In 1993, the Reseau de revue d’utilisation des medicaments (RRUM) conducted a retrospective review of omeprazole use in 13 hospitals. At the time of this review, omeprazole was in the restricted formulary of the provincial drug plan. Altogether, 24% of the acute treatments with omeprazole were initiated outside the hospital. Results showed that only 45% of in-hospital prescriptions for omeprazole were appropriate with regard to indications for acute therapy. According to these criteria, use of omeprazole was appropriate for the treatment of duodenal ulcers refractory to H2RA, gastric ulcers confirmed by endoscopy and refractory to H2RA, reflux esophagitis refractory to H2RA or proki-netic drugs, moderate or severe reflux esophagitis confirmed by endoscopy, and Zollinger-Ellison syndrome. The appropriateness of omeprazole prescribing was, therefore, lower in this review of omeprazole use than in the present study. There are many possible explanations for this difference, including variation in population characteristics, variability in physician prescribing habits, discrepancy in length of the studies, and difference in the data collecting methods and indicators of good prescribing practice used.

In our study, prescribing by general practitioners was significantly more questionable than prescribing by gastroenterologists. In 1991, a similar finding was observed by Moride et al in a study aimed at identifying determinants of suboptimal antiulcer medication use among elderly participants of the Quebec drug plan. One of the predictors for unusually short term use of antiulcer medications was prescribing by a general practitioner. Gastroenterologists may be more familiar with consensus guidelines in their discipline than are general practitioners. Gastroenterologists may also be more likely to prescribe omeprazole as a second-line therapy because they are consulted later in the course of the illness. Further studies should focus on the identification of factors explaining why suboptimal prescribing is associated with the prescriber’s specialty. Find very low prices on non-prescription drugs – cialis professional 20 mg for smart customers.

During the study period, some therapies using a combination of omeprazole and an antibiotic were recommended by, among others, the National Institutes of Health Consensus Development Conference on Helicobacter pylori. We considered the concurrent use of omeprazole and amoxicillin, clarithromycin, metronidazole or tetracycline as an indication for H pylori eradication. Because these antimicrobial agents may be used over seven to 14 days of treatment for a wide array of indications, this particular criterion may have overestimated the appropriateness of omeprazole prescribing. Nevertheless, such overestimation is probably very small because only 4.9% of patients received their first omeprazole prescription at the same time that they received an antibiotic prescription.

The literature published before 1996 supported the use of omeprazole as a second-line alternative to an H2RA in the treatment of peptic ulcers, and to an H2RA or a prokinetic drug in the treatment of uncomplicated gastroesophageal reflux disease. However, we were unable to assess indication for use, trial duration and posology of former treatment with an H2RA or a prokinetic drug. Therefore, the criteria used to define appropriate second-line therapy as an H2RA or a prokinetic drug taken in the previous six months may have led to an overestimation of appropriateness.

According to Tamblyn et al, the prescription claims database of the RAMQ may be one of the most accurate sources of information on drugs dispensed to individuals. Nevertheless, there are still some limitations to the use of this administrative database in studying ambulatory drug prescribing; for example, most clinical factors that could justify the selection of a drug are not recorded in it. Consequently, only prescriptions that are potentially inappropriate can be screened in a drug use review such as this. To judge definitively the quality of drug use, further indepth review of deviant cases is required. Such a review would likely reveal a higher level of appropriateness of use than was found in the present study.

Since 1996, indications for the use of omeprazole have changed. For instance, prescribing a double therapy for H pylori eradication is no longer supported by the consensus guidelines; only triple and quadruple eradication regimens are recommended. Further research is needed to evaluate the current quality of omeprazole prescription.

In June 1996, a universal public drug plan was implemented in Quebec; since then, the annual contribution of the elderly to the drug plan has increased. Whether this change in program modalities affected the appropriateness of omeprazole use in Quebec’s elderly population is unknown.

The present study suggests that the level of appropriateness of omeprazole prescribing might not be lower in a program where a drug is listed without restriction than in a more controlled environment. In Canada, there is wide variation across provincial drug plans in terms of eligibility, copayments and conditions for reimbursement of drugs in formularies. To what extent this variation translates to the quality of prescribing warrants further research.