Phenylazopyridine Hydrochloride Poisoning

Acute renal failure due to phenazopyridine (Pyridium®) overdose: case report and review of the literature

“…The typical onset of presentation is with gastrointestinal irritation, abdominal cramps, nausea, vomiting, and sometimes diarrhea. The yellow discoloration of the skin is described in most of the case reports as well as the orangebrown color of the urine [3,5,11,23,24]. This skin pigmentation is usually without hyperbilirubinemia, with normal liver enzymes, and without scleral icterus [3].…”

“…The most common side effect is mild gastrointestinal discomfort [2]. Methemoglobinemia, Heinz body hemolytic anemia, liver toxicity, skin pigmentation as well as acute renal failure are described with the use of Pyridium® [3][4][5][6][7][8][9][10][11][12][13]. It is primarily excreted by the kidneys; 90% of a single dose is cleared within 24 h. Approximately 40% of the excreted drug is unmetabolized phenazopyridine [16] while the remainder is composed of the potentially toxic metabolites p-aminophenol, N-acetyl-p-aminophenol, and aniline [15].…”

“…Pyridium® toxicity in humans can be due to excessive ingestion as a single dose or accumulation of therapeutic doses over time with underlying renal pathology [3,10,11,15,23,24]. The evidence in the literature suggests a syndrome-like presentation in Pyridium® toxicity.…”

“…At higher ingested doses, acute liver damage has also been shown in both animal studies [19] and clinical case reports [24]. Less than half of the papers report cyanosis or document methemoglobinemia [8,11,15,18]. However, it should be noted that, depending on the ingested dose and time at presentation, these findings might be easily missed.…”

“…Acute renal failure (ARF) is a rare but reported side effect [3][4][5][6][7][8][9][10]. Methemoglobinemia, hemolytic anemia, and skin pigmentation accompanies the transient renal failure in some of the reported cases [11][12][13][14][15]. We report a case of acute renal failure due to suicidal Pyridium® overdose in a young female with no prior documented kidney disease despite being infected with human immunodeficiency virus (HIV).…”