New British Horseracing Authority anti-doping rules, which include a zero-tolerance approach to anabolic steroids, will come into force from Monday.
A horse must not be given an anabolic steroid at any point in its life and will face a mandatory stand-down period from training for 12 months, and be ineligible to start in any race in Britain for 14 months, if found to have been administered such a substance.
All horses must be available for testing at any time after they are registered with the General Stud Book.
Horses born in Great Britain must also be registered with Weatherbys within 12 months of birth, phased to six months in two years.
Permanently imported horses must be registered with Weatherbys within 90 days of arrival in Britain, accompanied by a sample that shows no evidence of administration of anabolic steroids or other substances banned at all times.
Horses imported from Ireland, France and Germany that have spent 12 months under their equivalent policies will be exempt from this requirement as those countries boast similar policies, while runners from those nations will be treated as British runners and sampled as per the standard testing policy.
All other foreign runners must be in Britain, and BHA notified of their whereabouts, a minimum of 10 business days in advance of their intended race to facilitate post-arrival sampling and analysis - the results of which will be received prior to the horse running.
The new regulations have been welcomed by the National Trainers Federation.
NTF chief executive Rupert Arnold said: "The NTF has been working with the BHA to ensure the guide is clear.
"We are pleased to have contributed and are grateful to the trainers who have given us helpful feedback."
A review of the steroids issue was prompted by the Mahmood Al Zarooni scandal in 2013, when the trainer was found to have administered banned substances to a number of horses in his care.
BHA chief executive Nick Rust believes it was important to have reviewed the subject and to "never be complacent" in light of the Al Zarooni case and that of fellow trainer Gerard Butler, who was banned for similar offences in 2013.
Rust said: "Following the events of 2013 it was essential that the BHA ensured that British racing would remain at the forefront of a critical topic for not only racing but all modern sports.
"The enhanced, zero-tolerance rules represent exactly that.
"The BHA will continue this role and ensure that British and international racing does all within its power to remain at the forefront of combating doping.
"We hope that the steps we have taken will lead other nations to follow suit and implement rules that are as stringent as ours, for the good of the sport and the horse.
"There is no current evidence that the use of anabolic steroids or other similar substances is endemic in British racing.
"We showed in 2013 that when it does take place we are able to detect it and act on it.
"But we must never be complacent."
Jamie Stier, BHA director of raceday operations and regulation, said: "The new rules mean that there are extended responsibilities for owners, trainers and breeders to ensure that they comply with the zero-tolerance policy.
"However, we have taken care to ensure that these are not overly onerous and that the correct communication and support is in place.
"Similarly, connections of international runners now have extra responsibility when running horses in Britain."
Hair sampling, alongside existing blood and urine tests, will form an important part of the BHA testing procedures in the longer term.
Stier said: "The use of hair sampling will prove to be a significant tool in our armoury.
"The ability to detect substances which have been administered over an extended time frame will present opportunities and a level of deterrence which was not previously in place.
"The objective of the new rules is not that they will be imposed retrospectively and, thus, we do not see hair sampling being used extensively upon implementation, but it will become more prevalent as time goes by and the new rules bed in."