April 14th, 2023

Webinar Review: Urinary Sphincter Mecahnism Incompetence (Usmi) An Introduction To Caniphedrin

This veterinary webinar is sponsored by Chanelle Pharma and is one of several from the company in its CPD series.  Jonathan Moore has had an interesting career to date with a total of 12 years in equine practice, six years with Elanco in a sales and marketing role with many species, and since this year with Chanelle Pharma as the UK support manager. Along the way he found time to study for an MBA at the University of Southampton. 

The content of the webinar is as follows: 

  • Background on urinary incontinence in bitches

  • Diagnosis and treatment options

  • Caniphedrin: an update

We begin with a brief revision of the canine urogenital anatomy with a colour line diagram of the interior of the bladder, noting the site of the urinary sphincter. This is followed by a description of the process of normal urination and how continence is regulated. This is well illustrated by means of a flow diagram (no pun intended!) showing the importance of sympathetic innervation of the urethral sphincter. This comprises internally urethral smooth muscle and externally striated muscle, with continence further aided by the elasticity of urethral wall tissue, the length and diameter of the urethra and engorgement of sub-urethral venous plexuses.

We now move on to clinical revision noting that 82% of urinary incontinence is due to urinary sphincter mechanism incompetence (USMI), with 4% ectopic ureters, 2% cystitis, 2% neoplasia and others at 10%. There are further statistics on USMI with the problem mainly affecting large dogs (6 breeds are listed), after spaying. The mechanism of USMI is not fully understood, but it often occurs post neutering with a reduction of circulating hormones weakening the sphincter. Other possible causes are discussed, but the affect of neutering is clear with the risk of developing incontinence eight times higher in spayed bitches. There is no difference between ovariectomy and ovariohysterectomy. The timing of surgery, before or after first heat is one for individual vets to make, as opinions differ. There is a little more detail on the effects of neutering on hormones and the lower urinary tract before a summary of the diagnosis of USMI. This is obtained by: 

  • Signalment

  • History

  • Exclusion of other causes-urinalysis, blood chemistry, ultrasonography of bladder and abdomen

  • Urodynamic studies (usually referral) –but most vets will diagnose based on the response to treatment.

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Treatment options are medical (first line) and surgical (second line) with the latter mentioned here but not discussed. The main medical options are sympathomimetics or oestrogens. A third option, GnRH analogues are off licence in the UK.  The mode of action of the first two is outlined. Both ephedrine (Caniphedrin) and phenylpropanolamine/ephedrine are metabolised to noradrenaline, which leads to increased urethral sphincter smooth muscle tone. Oestrogens exert a similar effect by upregulating alpha-adrenergic receptors in the urethral sphincter.

The final part of the webinar details product information on Caniphedrin, with a comparison to phenylpropanolamine. Efficacy between the two is virtually identical but with caniphedrin only requiring once daily dosing. Tablets are 5 mg and 20 mg and a chart simplifies dosing instructions.  Starting doses are given for an initial ten days then reducing to half or less. Continuing on the initial dose indefinitely is ‘off label’. There is a good summary of possible adverse reactions and contraindications.

The key points in the last slide list the main advantages of the newly licensed product: 

  • Once a day dosing-easy to manage, reduced chance of desensitisation with long term use

  • Easy to administer dividable tablets

  • Comparable efficacy to phenylpropanolamine

  • Long lasting pack sizes -2 pack sizes of 100 tablets.

There is a full list of relevant references and to view more of Chanelle Pharma’s product rage and access more CPD you can register at:


I found this webinar to be very well presented and an excellent update for this fairly common condition. It has just the right amount of basic science and clinical information, and is not overly long at around 40 minutes making it ideal for a lunch and learn session for the whole practice- vets, nurses and support staff. There were some interesting questions of ten minutes or so to finish off, always a good indication of an engaging webinar.  

Urinary Sphincter Mecahnism Incompetence: An Intro To Caniphedrin

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