Absorption of alkalized intravesical lidocaine in normal and inflamed bladders: a simple method for improving bladder anesthesia.

PURPOSE

Pharmacokinetic studies have shown that intravesical lidocaine is not sufficiently absorbed by human bladders to achieve significant serum levels and it only provides a superficial local anesthetic effect. We investigated the pharmacokinetics of alkalized intravesical lidocaine in healthy volunteers and patients with interstitial cystitis to determine a safe dose of buffered lidocaine, the effect of interstitial cystitis on lidocaine uptake and the acute local anesthetic effect on bladder pain in interstitial cystitis.

MATERIALS AND METHODS

An initial dose finding study was done in 12 healthy volunteers using 4, 5 and 6 mg./kg. 5% lidocaine buffered with 8.4% sodium bicarbonate. Serial lidocaine levels were measured for 3 hours. Serum measurement was repeated in 12 patients with interstitial cystitis using 5 mg/kg. 5% lidocaine with sodium bicarbonate daily for 2 days. Patients rated pain before and during treatment.

RESULTS

Healthy volunteers and patients with interstitial cystitis had similar lidocaine absorption profiles with a peak of 1.06 microg/ml. (range 0.66 to 1.71) and 1.3 (range 0.2 to 2.0) at about 30 minutes. Mean pain score in the interstitial cystitis group decreased from a baseline of 6.0 to 1.8 on day 1 and 0.6 on day 2. There were complaints of urethral discomfort after voiding the buffered lidocaine in each group.

CONCLUSIONS

Alkalization provides safe and predictable lidocaine absorption into the bladder, as indicated by therapeutic systemic levels in healthy and inflamed bladders. Furthermore, the decrease in acute pain scores in the interstitial cystitis group indicated a concentration of local anesthetic within the bladder wall that was sufficient to block the sensory neurons within the submucosal plexus.