[Effect of sublingual oxybutynin in postoperative pain after radical retropubic prostatectomy]

Total prostatectomy (TP) is one of the referential treatments of localized cancer of the prostate gland. Urethrovesical anastomosis and urinary catheterization may be sources of strong contractions of the detrusor muscle responsible for intense pain which is added to parietal pain. This study evaluates the efficiency of oxybutynin in the treatment of this postoperative pain (POP).

Forty-five patients due to benefit from a TP by laparotomy were included in this prospective study. A urinary catheter was put in place during the operation. Patients were randomly split into two groups in the postoperative care room. Group P (n = 23) received a placebo in tablet form and group O (n = 22) received 5mg of oxybutynin in sublingual form. The POP was evaluated every 2 hours using the Visual Analogue pain Scale (VAS 0:10).

The accumulated dose of tramadol after 8 hours was 110.8 mg in group P and 39.7 mg in group O (p < 0.05). For group P, 15/23 of the patients (65%) were in pain versus 4/22 (18%) in group O. The VAS scores of group P were higher (4.1 +/- 1) than those of group O (1.2 +/- 0.9). For group P, when the PCA dose of tramadol was inefficient, a tablet of oxybutynin 5 mg brought the VAS scores down to the same level of those of group O within 2 hours. No side effects linked to the antimuscarinic action were observed.

Oxybutynin given in sublingual form reduced, at postoperative stage, the frequency and intensity of pain linked to the bladder wound and to the catheter after TP. Its use for the POP of the bladder section reduced the consumption of postoperative analgesia.