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October 30, 2024
Phenazopyridine (Pyridium) is a urinary analgesic that’s been around for over 100 years.1-3 In fact, the Food and Drug Administration (FDA) considers it a “grandfathered” drug, so safety and efficacy data from clinical trials is limited and its therapeutic role is based primarily on clinical observations.1,2 It’s solely a urinary analgesic (through an unknown mechanism) – it doesn’t resolve urinary tract infections (UTIs).1-4 As such, it’s primarily utilized in conjunction with antibiotics to provide short-term relief from urinary discomfort associated with lower UTIs, although you may occasionally see it used for symptomatic relief of dysuria from other causes (e.g., radiation induced cystitis).1-4
Phenazopyridine is available via prescription as 100mg or 200mg tablets and over-the-counter (OTC) as 95mg or 99.5mg tablets.4 The OTC products are often less expensive.4 The labeled dosing in patients with normal renal function is 200mg (or 2 OTC tablets) three times daily for up to 2 days.4 Courses of therapy beyond 2 days generally aren’t recommended to prevent masking UTI symptoms not improving with antibiotic therapy and to reduce risk of adverse effects, although reports of longer durations exist.1-4
Phenazopyridine is generally safe and well tolerated, but adverse effects, some serious, are possible. Most patients will experience harmless reddish-orange discoloration of bodily fluids (e.g., urine, tears). It can also cause nausea, vomiting, diarrhea, headache, rash, and itching.1-4 Rarely, it can cause severe adverse effects like acute renal failure, methemoglobinemia, hemolytic anemia, and jaundice, which appear to be more likely to occur when used at higher doses or longer than recommended, although there are case reports of severe adverse effects with typical dosing.5-11
Characteristics indicative of severe adverse reactions are described in Table 1.
| Table 1: Presentation of Severe Phenazopyridine Adverse Reactions2,5-11 | |
|---|---|
| Renal failure | • Confusion • Decline in urine output from baseline • Edema • Itching • Nausea / vomiting |
| Methemoglobinemia | • Cyanosis • Dizziness • Extreme fatigue, weakness and / or dyspnea • Headache |
| Hemolytic anemia | • Dark urine • Extreme fatigue, weakness and / or dyspnea • Jaundice • Pallor |
| Jaundice | • Yellowed skin, sclera |
Because phenazopyridine is primarily eliminated by the kidneys, patients with renal impairment are at an increased risk of experiencing severe side effects. As such, drug labeling recommends avoiding phenazopyridine in patients with a creatinine clearance < 50ml/min.4,7,9
Since hospice care is palliative in nature, an argument could be made that the benefit of improved dysuria symptoms outweighs the potential risks of adverse effects. And considering that there aren’t tons of urinary analgesics to pick from, it’s potentially reasonable to prescribe phenazopyridine to hospice patients with dysuria beyond its typical duration or to those with renal impairment. In those cases, patients and caregivers should be apprised of potential risks and benefits in a shared decision making process with the hospice interdisciplinary team and close monitoring should ensue. For those with renal impairment, reduced doses (e.g.,100mg or less) and extended dosing intervals should be considered, despite a lack of formal recommendations.9 If phenazopyridine toxicity is suspected, discontinuation followed by supportive care is recommended.
Written by: OnePoint Patient Care Clinical Team
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