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New Anticonvulsant Drug

A New Anticonvulsant - Pexion® (Imepitoin)

Pexion is a new anticonvulsant drug manufactured by Boehringer-Ingelheim (makers of Metacam) and launched at the beginning of April 2013.  I have put some information together and will update it as I hear more but as always you should check with your vet.

Pexion is a prescription-only medication designed to reduce seizures.

  • Tablets are oblong, white and carry the logo “I 01” for 100mg and “I 02” for 400mg tabs.  They are scored for cutting and supplied to the vet surgery in 100 or 250 tablet bottles. Pexion is not a controlled drug and I hope clients will, therefore, be able to buy it in larger doses to save money on dispensing fees. 
  • The active ingredient is imepitoin which does not have a bitter taste.  It is described as a new chemical entity and has not been used in humans. Other ingredients are microcrystalline cellulose, hypromellose, lactose mono-hydrate, sodium starch glycolate, magnesium sterate ad purified water all of which have been used in other oral veterinary medicines. 
  • The drug is eliminated in the faeces and is reported as being safe for the liver However it should not be used in dogs with severely impaired liver, kidney or heart function.
  • Requires only a short time to get into the system (up to one week).
  • Has to be given twice daily although it is noteworthy that the company say that missed doses should be left until the next dose is due. The company have assured me that this is correct.
  • The dosage requires monitoring initially but when the therapeutic dose is reached, no further level checks are required.
  • The company has assured me that problems with side effects are going to be less than with other anticonvulsant drugs.  Side-effects that have been reported include increased hunger, thirst, activity levels and mild gastrointestinal upsets. The company says that if any of these do occur, they usually go away over time. The European Medicines Agency lists them as follows -  Mild and generally short-lived side effects with Pexion were polyphagia (excessive eating), hyperactivity, polyuria (increased volume of urine), polydipsia (excessive water intake), somnolence (sleepiness), hypersalivation, emesis (vomiting), ataxia (inability to coordinate muscle movements), apathy (lack of interest in surroundings), diarrhoea, prolapsed nictitating membrane (protrusion across the eye of the ‘third eyelid’), decreased sight and sensitivity to sound. For a full list of all side-effects reported with Pexion, see the package leaflet.
  • Toxicity testing has been carried out and the signs to look for are – in addition to the sides effects already mentioned – decrease in appetite and body weight, heart rate and temperature, anaemia, and effects on the liver and kidneys although the studies showed that these effects were reversible after 6 weeks off the drug except for those dogs on the highest drug doses.  At these levels other side-effects were noted, particularly affecting reproductive organs.
  • Pexion has not been evaluated for use in status epilepticus or cluster seizures and is not advised as the primary treatment in these cases

The drug website only gives basic information whilst that provided by the European Medicines Agency is much more detailed and well worth reading but do keep an open mind – they have to include all possibilities.  After a study of 226 dogs the efficacy of Pexion was very slightly less than phenobarbitone but with fewer side effects.

Please note that this article should be used for information only.  As always, you should consult your vet for definitive information.

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