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Administration

Adult Dosage, Dosage Forms, and Strengths

Typically, phenazopyridine is prescribed at a dosage of 100 to 200 mg 3 times daily for healthy adults. Over-the-counter (OTC) tablets are obtainable in lower strengths, ranging from 50 to 99.5 mg. The OTC tablets are frequently taken 2 at a time, 3 times daily, effectively matching the prescription regimen. The OTC formulation is a valuable option for temporary symptom relief while awaiting additional medical attention. To prevent stomach discomfort, phenazopyridine is advised to be taken with or after meals.[12]

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The recommended phenazopyridine treatment duration is 2 days, and this short period provides swift relief from discomfort until antibiotics can effectively manage the infection and safeguard the patient from potentially severe adverse effects. Certain clinicians recommend that individuals experiencing uncomplicated UTI symptoms take OTC phenazopyridine alone for 5 days, expecting the infection to resolve spontaneously. However, most patients favor a more assured resolution, and while the practice is not yet substantiated, it is noteworthy that a 5-day therapy duration exceeds the current recommendations.

The drug is commonly used to enhance comfort among outpatients with uncomplicated UTIs. However, phenazopyridine is not routinely included in treatment protocols for complicated UTIs or inpatient scenarios addressing acute pyelonephritis in patients with risk factors for heightened infection severity.

Diagnostic use

A study indicates that the oral administration of phenazopyridine with dextrose instillation can effectively facilitate the visualization of ureteral patency during intraoperative cystoscopy.[13] Administering a single 200 mg dose of phenazopyridine to the patient on the evening before the surgical procedure aids in identifying the urethral orifice.[14] However, phenazopyridine is not valuable as a diagnostic tool for detecting incontinence or premature membrane rupture.[15][16]

Cystoscopy use

In a randomized controlled trial, 97 patients undergoing cystoscopy received either 200 mg of phenazopyridine along with lidocaine gel or lidocaine gel alone. The medications were administered in 3 doses, starting with a dose administered 20 minutes before the procedure and then every 8 hours thereafter. Participants who were administered phenazopyridine and lidocaine gel reported experiencing less discomfort and exhibited lower heart rates than those who received only lidocaine gel. The authors concluded that phenazopyridine reduces the intensity of pain associated with both cystoscopy and the initial act of urination.[17]

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Postoperative use

In a randomized controlled study involving 152 women undergoing prolapse surgery, administering a single postoperative dose of phenazopyridine at 200 mg did not demonstrate enhanced postoperative voiding compared to the control group.[18] In a retrospective cohort study involving 149 women who underwent a retropubic mid-urethral sling operation, phenazopyridine was reported to improve postoperative voiding.[19]

Radiation-induced cystitis use

Phenazopyridine has been used safely for up to 2 months as a form of supportive care in cases of radiation-induced cystitis.[20]

Specific Patient Populations

Renal impairment: For individuals with mild renal impairment, with a glomerular filtration rate of more than 50 mL/min, the recommended dosing frequency is every 8 to 16 hours. Phenazopyridine should not used in patients with a glomerular filtration rate of less than 50 mL/min.[21]

Hepatic impairment: Phenazopyridine is contraindicated in cases of severe hepatitis.

Pregnancy considerations: Phenazopyridine is an FDA pregnancy category B drug known to cross the placenta.[16] Phenazopyridine should be used in pregnancy only if it is indicated.

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Breastfeeding considerations: The safety of phenazopyridine is not established during breastfeeding. Therefore, phenazopyridine is not recommended during lactation due to its potential to cause methemoglobinemia and hemolytic anemia, especially in infants with glucose-6-phosphate dehydrogenase (G6PD) deficiency.[22]

Pediatric considerations: The recommended dosage for children aged 6 to 12 is 12 mg/kg/d, divided into 3 equal doses. A specialized pediatric formulation is not commercially available and requires compounding.[23] Although review articles and consensus publications addressing the treatment of pediatric UTIs exist, they do not typically reference the use of phenazopyridine.[24][25]

Older patients: It is advised to consult renal dosing guidelines for older patients.

Clinical Studies

Phenazopyridine was marketed before the implementation of regulations that mandated preclinical studies to establish a drug’s safety and efficacy. Consequently, comprehensive and substantial studies are lacking, and the drug’s role in UTI treatment primarily relies on clinical observations.

A critical analysis of the available studies has been published. Among these studies, 1 encompassed 118 patients, of which 64% of the participants had cystitis or pyelonephritis. All participants were administered phenazopyridine at 200 mg, 3 times daily, for 2 weeks, exceeding the recommended duration. The analysis was conducted as an open-label, single-arm study. The authors documented enhanced symptomatic responses, including alleviation of dysuria (95.3%), burning sensation (93.6%), frequency (85.6%), and nocturia (83.7%).[1]

Another investigation involved 49 subjects with acute UTIs who received phenazopyridine at a dosage of 200 mg administered 3 times daily. After 24 and 72 hours, patients underwent evaluations for nocturia, burning, and urgency symptoms. Mean symptom scores were reported as slight, with 3 or 4 symptoms after 24 hours and none, with 1 or 2 after 72 hours.[26]

Phenazopyridine was compared to flavoxate, an antispasmodic drug, in a study involving 392 participants displaying UTI symptoms, incontinence, and/or suprapubic pain. The participants were administered either phenazopyridine at a dosage of 200 mg 3 times daily or flavoxate at a dosage of 100 mg 4 times daily. The variances in clinical response did not demonstrate statistical significance. In a separate analysis of men with prostatitis, the participants were subjected to a regimen of phenazopyridine at a dosage of 200 mg 3 times daily. Only 31% of the subjects reported satisfactory relief from symptoms.[12]

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