If there is no information leaflet that comes with a specific medication, looking on the website for information about the drug is better than nothing.
Another excellent source is your pharmacist and in the UK if you do have a query on medication or symptoms, the chemist (pharmacist) can give you excellent advise.
For lay people a "smaller sanitized version prepared by the manufacturer." is far better to understand than to be bombarded with a lot of technical jargon.
The most appropriate place to start a search on side effects of a given drug is not the manufacturers promotional website. The United States Food and Drug Administration maintains a website with every drug approved for use in the United States, along with the regulatory history and generic equivelant. You can look up any specific drug and obtain the approval history. And the FDA list of side-effects.The FDA site also has a form to report a potential adverse effect. It is important to tell the doctor you have made such a report and include the manufacturing lot number of the drug.
If you have side effects square one is to immediately stop taking the medication, not to "notify your doctor", although that should be done.
The product information leaflet cited by the above poster is not complete. It is a sanitized version prepared by the manufacturer. The only complete information on drugs is in the PDR or physician's desk reference, which is available on the net, and in the U.S. database "Pubmed". Type in "Medrol" and "side effects". When you purchase a prescription drug ask them foir the "package insert". Commonly the drugstores pass out a smaller sanitized version of the studies and side effects.
The precautions with taking this medication does list the following:
Tell your doctor right away if you have any serious side effects, including: unusual weight gain, menstrual period changes, bone/joint pain, easy bruising/bleeding, mental/mood changes (such as mood swings, depression, agitation), muscle weakness/pain, puffy face, slow wound healing, swelling of the ankles/feet/hands, thinning skin, unusual hair/skin growth, vision problems, fast/slow/irregular heartbeat.
Your heart palpitations would come under "fast/slow/irregular heartbeat".
If you have had a product information leaflet with your medication, you can view this on line:
http://www.rxlist.com/medrol-drug.htm
Do contact your doctor or make an appointment to see him as soon as possible. When you telephone the surgery do make them aware of the urgency and what the problem is.
An irregular heartbeat can be (but is not necessarily) one of the side effects of Medrol. Immediately cease use of the medication, file an FDA adverse effects form (see their website), and consult your primary care physician. People have different genetic tolerances to this product.