Teva Cetirizine Dihydrochloride Vs Cetirizine Hydrochloride-Legal problem??

[LFCMad]

Hi all,

I'm a newly qualified locum and had a script for "Cetirizine Hydrochloirde" tablets. The pharmacy didnt have any hydrochloride but had "Cetirizine Dihydrochloride" tablets from Teva and always said they had given those in the past. Having done a pharmaceutical chemistry course previous I know that structurally they are different, probably negligible in clinical difference. But since the script stated "Cetirizine Hydrochloride" is that all that can be legally given? The superintendants department for the store said that it is fine to dispense the dihydrochloride version as they are the same. I have looked up the structures to make sure and they are not the same. I suspect it is a patent dodge to get a cheaper version in the dispensaries. Has anyone had this scenario also? And what do you recon the legal standing is on dispensing? Thanks.

[johnep]

Had all this before with several products. If a company can find some obscure acid and use this to make the salt, then helps prevent others from copying. Cannot quite recall case but believe was amlodipine.
johnep

[Pharmanaut]

Had all this before with several products. If a company can find some obscure acid and use this to make the salt, then helps prevent others from copying. Cannot quite recall case but believe was amlodipine.
johnep

Besilate, Mesilate and Maleate.
Patent expired first on Mesilate and Maleate leaving scripts written as generic no salt dispensable as either mesilate or maleate, but scripts written as Besilate had to be dispensed as brand.
It certainly makes our job no easier.

on a similar subject our local surgery always prescribes by AMP for some reason.
We get prescriptions for abc 10mg Tablets (AAH Pharmaceuticals)
Which is meaningless as AAH send whatever they have got.

I guess its only us that are bothered - everyone else doesn't seem to care if a legal document is written incorrectly.

[Shop Designer]

I am not a Pharmacist, (but, do have a Chemistry diploma) the hydrochloride and dihydrocloride are the same atomic structure and are a carrier as such there would be almost nothing to differentiate them in base form, as such I would (were it me???) see these as an interchangeable product with each other? I have to conclude the OP is right that there is actually a patent "dodge" on this benign salt aspect?

I am keen to know if this assumption would be right or wrong though.

[johnep]

Patent 'dodges':
Long Acting form (even if original naturally long acting) eg doxasozin.
Different enantiomer. Cetirizine prime example.
Different salt where patent specifies salt.
Different form ie tablets instead of capsules eg Ramipril.
johnep

[LeftArm]

Works particularily well if you stop manufacturing the original product before the patent expires so that patients are obliged to swap to the new formulation.

[weeneldo]

I have never, ever heard of anyone suffering any ill effect or of any literature mentioning a difference in activity between salts of Cetirizine (unlike drugs such as Perindopril and Diclofenac). I've also never heard of any pharmacist making a problem out of it in practice and I imagine that if any pharmacist did try and insist on the exact salt being dispensed, they would be hated by literally everyone else involved in the entire process from the GP, to the dispensary staff, to the patient. I'd say if you're not sure about differences between salts, look it up in the BNF. If it doesn't say anything about differences between salts, dispense it.

[Raju]

If one were to take a strict legal position, I believe it is not legal to dispense a different salt. However, I cannot imagine any problem with the patient, prescriber and even the regulator in the case of cetirizine hydrochloride and cetirizine dihydrochloride.