There have been some changes in regulations for 2015, affecting some commonly-used medicines, so it’s as well to be aware of what is and what is not allowed.
The full list of banned substances, just in case you take anything unusual, is here. A more readable guide to recent changes, written for a triathlon magazine, is here. UK Anti-Doping’s summary is here.
The main things likely to be relevant are :
Cold Remedies : a lot of substances are permitted now, so you can check the ingredients list of your favourite against the full list above. The rest, generally, are permitted out-of-competition, but should not be found in your blood / urine after an event. In general, don’t take any in the 24 hours before a race and you will be OK. If you were even thinking of racing with a cold in the first place!
Asthma medications : you are advised to ask your pharmacist how many ‘puffs’ will give more than 1600 micrograms of albuterol or 54 micrograms of formoterol in the span of 24 hours. If you need more than this, you need to get a Therapeutic Use Exemption certificate.
Caffeine : has been a prohibited substance above a certain level in previous years, but apparently isn’t one any more. Drinking 20 cups of coffee before a race is still not advised !
Plasma donation which a few people do, is now banned, as the process increases the concentration of red blood cells.
There are more details under the links above – I am obviously no expert, so you are encouraged to check out the proper information if you think any of the above might affect you.