What it means
After a drug name, such as bupropion SR, it means sustained-release: the tablet releases the drug slowly over many hours. On an ECG report, SR or NSR means sinus rhythm or normal sinus rhythm, the heart's normal beat starting in the sinus node. In anatomy, SR can mean sarcoplasmic reticulum, which stores calcium in muscle cells. Read it in context.
For the nurse
Sustained-release tablets are swallowed whole and never crushed or chewed.
Related terms
electrocardiogram
A test that records the heart's electrical activity as waves on paper or a screen.
XR
An abbreviation with two common meanings: extended-release (after a drug name) or x-ray (in an imaging order).