Abbreviations: ASSB, Santa Barbara Health Area; CCSS, Costa Rican Social Security; CCD, “Dr. Carlos Duran

Cartín” Clinic; DDD, defined daily dosage;HCG,“ Dr. Rafael Angel Calderon Guardia” Hospital; UTIs, urinary tract infection; LOM, official list of

medications. Sources of support: Completion of this work did not receive external economic contribution of others, nor was under conflicts of interest with pharmaceutical companies or other.

Correspondence: carlos.cfg@gmail.com
Drug Area and Therapeutics Clinic, Department of Pharmacoepidemiology, Costa Rican Social Security.

Abstract

Phenazopyridine is a urinary tract analgesic agent for oral administration. The drug is described as a dye group “azo”, whose chemical name is 2,6 diaminopyridine, 3 (phenylazo) Monohydrochloride. In 24 hours, 90% is excreted in the urine, 41% as unchanged drug and 49% as metabolites (most notably paracetamol), which exert a topical analgesic effect on the urinary tract mucosa.¹

Based on the principles of medicine based on evidence, el analysis of the available scientific information showed the lack of randomized clinical trials with the standard methodology of phase III the lack of systematic reviews with meth-analysis, to sustain the use of phenazopyridine as part of the management of urinary tract infections and other irritative syndromes. Existing information is scarce and of

poor quality according to current standards required by scientific publications.^2-9

Despite this, the drug is included in the Costa Rican Social Security (CCSS) official list of medications (LOM), in presentation of a 100mg tablet. Institutional experience of use of phenazopyridine over 20 years, with a historical profile of safety and effectiveness, and now, the institutional consumption projected about 1830 patients who take this medicine every day, based on the daily defined dosage (DDD) 600 mg / d10 orally, for its main indication as an analgesic for urinary tract infections.^{1, 11}

Under the rational use of medications developed with Social Security, the systematic and ongoing use of the drug in clinical practice, which contrasts with the weakness in the scientific information that supports the prescription, forms the basis for the study of drug use, in order to analyze the profile of phenazopyridine use in the context of routine clinical practice in outpatients, at different levels of attention and during a time period of 1 month.

Materials and methods

In order to meet this objective, an applied research design, observational, analytical approach, and approval of the Central Committee of the CCSS Pharmacotherapy for technology assessment in health studies paradigm drug use, according to the model prescription-indication, we proceeded at all times with a strict observation of the ethical principles confidentiality and non-malfeasance.

In analyzing the use of phenazopyridine in the context of clinical practice, as a first step the pharmacy was requested to release the drug during January 2011 in three selected units, one for each level of care: Santa Barbara Health Area (ASSB), Dr. Carlos Durán Clinic (CCD) and Dr. Calderón Guardia Hospital (HCG), with the purpose to prepare a quantative profile of use.

For qualitative analysis of prescription medication on a prescription-indication model, a random selection was made among all cases of drug clearance in each unit, during the period, seeking to have a random sample n = 30/unit. The sample size was defined for a minimum representation of 20% under the assumption of normality for compliance with the central limit theorem.

With emphasis on specific medical consultation that supported the prescription drug, a selective review of the medical records was made, prior to endorsement of the medical departments of the units; in a predesigned form and without identifying individuals, the information on diagnosis, and age, dose, duration and other quantitative variables was registered in an individualized way.

Data was recorded and processed in an Excel ® database for the initial descriptive statistical approach; tables and figures were designed, analytical phase of the results was developed and the comparative analysis was drafted.

Results

In the course of one month, three medical units dispatched 381 of the phenazopyridine prescriptions to patients seen, the vast majority of them, women; the prescription varied in the range of 3 to 90 tablets, although a high percentage of people (60, 43%) were given prescriptions and only 10 tablets sent for treatment (Table 1).

Discussion

This drug utilization study, designed to evaluate the usage profile of phenazopyridine in a pattern of prescription-indication, confirms that the drug is actually used as part of the management of urinary infections, which is attributed to its well known analgesic properties. In addition, as part of this intervention, it is validly associated with causal antibacterial treatment; this therapy jointly showed a strong tendency towards rational use in the first and second level of care.

An important aspect of the findings emerged from this work and based on a habit of prescribing, which also exceeds the pharmaceutical review for release of the medication, is the prescription of a sub-therapeutic dose of phenazopyridine, more than a third of the patients. According to available scientific evidence, it should be remembered that the dose for adults is 100 to 200 mg 3 times/day, and for a period of

two days, concomitantly with antibacterial treatment.^{5, 6,11}

In accordance with the principles of rational drug use, the findings of this study show that most patients use the drug for short period, with the prescription of about 10 tablets per treatment, primarily indicated for the relief in the case of UTI, and with antimicrobials, in the case of UTI. This profile of the drug use is consistent with international recommendations for the clinical use of the drug, as to encourage prescribing for patients with a diagnosis of UTI, for 2 days of treatment, and concomitantly with an antibiotic to resolve the ITU1, ^{5, 8, 11.}

However, in contrast to the above, it is unfortunate that 11% of patients diagnosed with UTI, were not prescribed an antimicrobial agent. Moreover, it is noteworthy that phenazopyridine is being prescribed to a variety of other diagnoses for which there is no scientific data to support its use in such conditions. The prescription of the drug, in such cases, it turns away from the principles of rational drug use, to nullify the benefit and maximize the inherent risks of the medication, as would be the occurrence of adverse effects. Similarly, the above consideration of the side effects, applies to the interactions derived from the frequent combination with other drugs. (acetaminophen, non-steroidal antiinflammatories, hyoscine).

In the medical files, prescribers documented various diagnoses during consultation, which merited urinary analgesic prescription and lead to dubious rationality questionable practice to alleviate this some degree of urinary mucosal irritation, as a symptom associated in case of gonorrhea, prostatic pathology and vulvovaginitis; however, no valid pharmacotherapeutic information is available to support this practice.

Based on information available from high-quality scientific literature ^2-9 and historical experience of institutional use, phenazopyridine is an effective analgesic of urinary mucosa, indicated for prescription for conditions with disuria and burning sensations, frequency and urgency associated with urinary tract infections, but without anti-infective effect; so it is imperative to note that during an ongoing infection, the antimicrobial agent is responsible for the final resolution, so that its prescription should not be omitted.

In conclusion, by analyzing the usage profile of phenazopyridine in the context of clinical practice at the level of general and specialized outpatient medical care, in the different levels of care, for a period of one month, in the paradigm of the principles of rational drug use, the study findings show that the use is partial and reasonably appropriate and, therefore, support the assumption of effectiveness for just over half of the patients, especially in the context of medical care in the first and second level of care, with a historical profile of security. However, the diversity in prescribing habits also highlights the need to improve the use, and it would be appropriate to develop actions to encourage more rational prescription, seeking to maximize the benefit for patients.