From the Guidelines
Pyridium (Phenazopyridine) works by directly acting on the urinary tract lining to provide pain relief, numbing the mucosa of the urinary tract, bladder, and urethra, reducing pain, burning, urgency, and discomfort during urination. The medication is a urinary analgesic that is commonly used to alleviate symptoms of urinary tract irritation, although data in the literature are limited, as noted in the aua guideline for the diagnosis and treatment of interstitial cystitis/bladder pain syndrome 1. Some key points to consider when using Pyridium include:
- It is typically prescribed at a dose of 100-200 mg three times daily for 2-3 days to treat urinary symptoms associated with infections, procedures, or irritation
- Pyridium does not treat the underlying infection and should be used alongside appropriate antibiotics when infection is present
- The medication works quickly, often providing relief within 24 hours
- It turns urine orange or red, which is normal but can stain clothing
- Patients should be aware that Pyridium is eliminated through the kidneys and works because it concentrates in the urine, allowing it to directly contact and soothe the irritated tissues of the urinary tract. While individual patients may find Pyridium to be worthwhile in alleviating symptoms, as noted in the aua guideline 1, it is essential to use the medication judiciously and under medical supervision to ensure optimal outcomes and minimize potential side effects.
From the FDA Drug Label
CLINICAL PHARMACOLOGY Phenazopyridine HCl is excreted in the urine where it exerts a topical analgesic effect on the mucosa of the urinary tract. This action helps to relieve pain, burning, urgency and frequency. DESCRIPTION Phenazopyridine Hydrochloride is light or dark red to dark violet, odorless, slightly bitter, crystalline powder. It has a specific local analgesic effect in the urinary tract, promptly relieving burning and pain.
Phenazopyridine works by exerting a topical analgesic effect on the mucosa of the urinary tract. The precise mechanism of action is not known, but it helps to relieve pain, burning, urgency, and frequency in the urinary tract 2.
From the Research
Mechanism of Action
- Pyridium (Phenazopyridine) works by acting on the bladder mucosa to produce a local analgesic effect 3
- It has been shown to reduce pain intensity during and after cystoscopy and alleviate pain during first urination 3
- The drug inhibits the TRPM8 channel, which is expressed in sensory neurons that innervate the bladder wall, thereby providing symptomatic relief of bladder pain 4
- TRPM8 inhibition may underlie the analgesic activity of Pyridium, as it is expressed in bladder afferent neurons and upregulated in patients with painful bladder disorders 4
Clinical Effects
- Pyridium has been shown to improve symptoms of uncomplicated urinary tract infection, including pain during urination and increased frequency of urination 5
- It has been found to be effective and well-tolerated in patients with acute uncomplicated cystitis, and can be recommended in addition to etiological therapy 5
- The drug has been associated with various adverse effects, including yellow skin discoloration, hemolytic anemia, methemoglobinemia, and acute renal failure, especially in patients with preexisting kidney disease 6, 7
Pharmacodynamics
- Pyridium rapidly and reversibly inhibits responses of TRPM8 expressed in HEK293 cells to cold and menthol, with IC50 values between 2 and 10 μM 4
- It acts by shifting the voltage dependence of channel activation towards positive potentials, opposite to the effect of menthol 4
- The drug inhibits TRPM8-mediated, menthol-evoked calcium responses in lumbosacral DRG neurons 4