Effect of caffeine on bladder function in patients with overactive bladder symptoms

Objectives: To evaluate the effect of caffeine at the dose of 4.5 mg/kg on bladder function in overactive bladder (OAB) adults. Materials and Methods: Nine women and three men aged 21-40 years with OAB symptoms were included. Each subject drank 8 ml/kg of water with and without caffeine at two separate sessions. Cystometry and uroflowmetry were performed 30 minutes after each drink. The effects of caffeine on urodynamic parameters were compared. Results: After caffeine ingestion, the mean volume at bladder filling phase decreased at first desire to void and normal desire to void (P<0.05), compared to the mean volume after taking water (control) drink. The mean volume at strong desire to void, urgency and maximum cystometric capacity also tended to decrease. No change in the detrusor pressure at filling phase was found. At voiding phase, the maximal flow rate, average flow rate and voided volume were increased (P<0.05). The urine flow time and time to maximal flow rate were not changed. Conclusion: Caffeine at 4.5 mg/kg caused diuresis and decreased the threshold of sensation at filling phase, with an increase in flow rate and voided volume. So, caffeine can promote early urgency and frequency of urination. Individuals with lower urinary tract symptom should avoid or be cautious in consuming caffeine containing foodstuffs.