Effectiveness of vaginally administered oxybutynin on rabbit bladder function.
OBJECTIVE
To demonstrate the effectiveness of vaginally delivered oxybutynin on bladder function. Oxybutynin has been used for treatment of urge urinary incontinence for more than 20 years.


METHODS
Thirty female New Zealand White rabbits were used for this experiment. Each rabbit was anesthetized, and the carotid artery was cannulated for blood pressure monitoring. The bladder dome was catheterized for both monitoring of bladder pressure and cystometry. After initial cystometry, acetylcholine (ACh) was injected into the vesical artery at 15-minute intervals for 4 hours. Cystometry was performed at the 2-hour mark and at the end of each experiment (4 hours). After the third ACh administration, vaginal or oral oxybutynin was given and the effect on the response to ACh, blood pressure, and cystometry was observed.


RESULTS
The high dose of oxybutynin completely inhibited the response to ACh and significantly inhibited the micturition reflex. A 45% inhibition of micturition pressure occurred at the intermediate dose. Little effect on compliance after the low dose and a significant increase in compliance after the mid-dose occurred. Both the low and intermediate doses of oxybutynin reduced the response to ACh to approximately 50% of control. No blood pressure effects of vaginal oxybutynin were noted for any concentration. Oral oxybutynin showed very similar effects to that of the intermediate vaginal dose.


CONCLUSIONS
Vaginally delivered oxybutynin was effective in decreasing bladder compliance and inhibiting intra-arterial ACh-stimulated bladder contractions with little or no effect on the vascular effect of ACh.
Levin
Robert M
RM
Albany College of Pharmacy, Albany, New York 12208, USA.
Whitbeck
Catherine
C
Borow
Abby
A
Burden
Opal
O
Leggett
Robert E
RE
D000109:Acetylcholine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000282:Administration, Intravaginal; D000284:Administration, Oral; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D005260:Female; D008333:Mandelic Acids / Q000008:administration & dosage* / Q000627:therapeutic use*; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D011817:Rabbits; D001743:Urinary Bladder / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology*; D014549:Urinary Incontinence / Q000188:drug therapy / Q000378:metabolism
D008333:Mandelic Acids; C005419:oxybutynin; D000109:Acetylcholine