Leroy Parry, 24, sank his teeth into the bicep of PC Gareth Phillips for nearly a minute.
Swansea Crown Court heard it took seven officers to restrain him.
Parry, from Waunarlwydd, was jailed for 20 months after admitting affray, assault occasioning actual bodily harm and three assaults on police.
PC Phillips described it as the worst violence in his 14-year police career, and said he had to punch snarling Parry three times before he let go of his dog-like bite.
The court heard Parry has been addicted to drug Spice for five-and-a-half years and was having withdrawals when he carried out the attack.
It happened during a disturbance in Swansea city centre on 7 April.
Prosecutor Tom Scapens said the officer described the pain as "excruciating from the outset".
Mr Scapens said: "He could feel this bite through a long sleeve work shirt and two fleeces.
"He said Leroy Parry was 'animal-like'.
"He was in so much pain he was going into shock."
The court heard the officer looked at his arm when he got into the police van.
Mr Scapens said: "Looking at it made him feel physically sick."
Parry later apologised to officers, telling them he was "clucking for Spice".
The drug Spice is the name commonly used to describe a laboratory-created cannabis substitute. It is banned in many countries, including the UK.
It has been blamed in recent months, along with another variant called Black Mamba, of turning users into "zombies" collapsing in the streets around Wrexham bus station in north Wales.
The court heard Parry had convictions for some 41 offences and a history of assaulting police officers.
Speaking after sentencing, Insp Mark Davies said Parry had carried out a "vicious attack".
"Nobody can justify this level of violence for somebody just doing their job," said Insp Davies.
"This incident demonstrates the very real potential dangers that officers face on a daily basis.
"When an officer leaves the station, they simply do not know what they might have to deal with at any given time."
A man addicted to the synthetic drug Spice was "snarling and growling" like an animal as he bit a police officer, a court has heard.