Hi there -- Welcome to Just Answer.
Is there any known reason for her not coming into heat ? any hormone levels taken etc?
There are a number of factors that might be in play here -- Yes -- PG 600 is approved for swine use -- and can be given extralable to dogs by a vet. However, having said that, it is not approved for this use in this species and results of efficacy and side effects in studies are not available -- so the risks are not able to be determined.
The best way to figure out why a dog is not coming into heat is to tract progeterone levels and see if there is any variance -- over time --
Also to visualize the repro tract via ultrasound --
As cyctic ovaries, uterine growths, and endocrine disorders can all cause this --
This testing, however, does have expense involved --
and is not a quick easy fix --
And the medication Lutalyse is not advised in dogs at all -- though used in other species --
There are breeders who discuss the use of PG600 from swine product -- but you will need a swine vet to administer and they will have to be willing to take the risks fo the medication.
Here is a link to some additional information -- though on a scottish terrier link -- it is good veterinary information on breeding, heat cycles, and infertility in general .
I am searching for any reliable information on the efficacy and side effects in dogs -- and am unable to find a good source --
I see that there can be pain with administration, multiple shots (2-3) -- and it is given in the leg muscle -- and that results vary
Found a published resource that reviewed a number of possible medicaitons used to bring dogs into heat --
But it is in abstract form and does not list the details in this format --
Biggest short term factors seem to be variable results, change in behavior, and unknown long term side effects and undocumnetation of short term health side effects ---
You may find more on a breeder forum for pitbulls and greyhounds -- but information is not from any published or data backed study .