I think you'll find that it is -
Publishers of http://www.oxforddictionaries.com are the Oxford University Press,
who are -
http://www.ox.ac.uk/ - Oxford University Press is a department of the University of Oxford. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide.
It is not from the same stable as the full OED.
Let me explain for people who have a problem with understanding
The OED is a multi-volume dictionary that is seen as the best source for English usage in England. It has thirteen volumes in the edition I have from about twenty years ago- the last print edition; it is called the Oxford English Dictionary. It has a smaller brother which in two volumes describes a reduced level of definition for each word; it is called the Shorter Oxford English Dictionary. There is the most commonly used single volume version; it is called the Concise Oxford English Dictionary.
About thirty years ago Robert Maxwell IIRC realised that there was a problem with the Trade Mark of the Oxfors Dictionaries, and as his affairs were conducted in Oxford at Paergamon Press, he started publishing what was essentially a knock-off dictionary published under the name Oxford Dictionaries.
Now OED had substantial records of all English usage going back over 150 years in their offices in St Giles. Maxwell's hacks in Pergamon Press produced cheap dictionaries using secondary materials as they squatted on the Oxfors name. These dictionaries have never been seen as serious competitors for the various other standards- Collins, Chambers, OED etc. Maxwell won a court case over the use of the name through the stupidity of the OED lawyers. More recently, the Oxford University Press bought out the new owners of the cheap Oxford dictionaries and are currently updating and correcting them to bring them into line with modern dictionary practice, in an attempt to save their reputation.
The Concise OED defines
sedation as "calming, especially by a sedative drug"
and
Sedative as tending to calm and soothe
and sedate as ...tranquil, equable, composed, settled, not-impulsive or lively or agitated.
None of these are quite how professionals use the terms which are:
Sedative- lowering agitation and encouraging clouding of consciousness
Analgesic- assuaging pain
Anesthetic- removing all pain
Hypnotic- encouraging sleep.
Let me assure you that if you were to have a minor operation ( brain removal for instance) and the doctor gave you only sedation rather than analgesia or anesthetic, you would be complaining.
Analgesia is not sedation. Sedation is not analgesia