NEW YORK (AP) _ Chronic and first-time cocaine users risk seizures, suicidal tendencies, paralysis and other serious complications, according to studies presented Wednesday.

''It's very clear there are a whole bunch of complications,'' said Dr. Daniel Lowenstein, chief neurology resident at the University of California- San Francisco.

''We clearly saw patients who claimed they'd never used cocaine before and had serious complications,'' he said. In addition, complications showed up in people who were using small or large amounts of the drug, and who took it by any of several means, he said.

At the annual meeting of the American Academy of Neurology, Lowenstein described 133 cases of cocaine users who came to San Francisco General Hospital between July 1979 and September 1986 because of neurological and psychiatric complaints.

Twenty-eight users complained of seizures, usually convulsions lasting four or five minutes, Lowenstein said. In two cases the seizures resisted standard treatment and doctors had to induce a coma to bring them under control, Lowenstein said. One of the victims is now institutionalized, he said.

Another 67 patients showed psychiatric disturbances, ranging from bizarre behavior to severe agitation, paranoia and depression, he said. Four jumped from buildings, and another nine developed a desire to commit suicide after using cocaine, he said.

Among first-time users, two had seizures, one became suicidal and tried to kill himself by overdose, and one suffered sudden but temporary weakness of the arm, leg and face on one side of his body, Lowenstein said.

Other complications in the study included nine cases of severe headache and five cases of severe dizziness, he said.

He stressed the study told only about complication severe enough to make a uservisit a hospital, and said the study did not tell how frequent the complications are among users.

''It's a dangerous drug,'' he said in an interview. ''It's playing Russian roulette. We just dont know how many bullets are in the chamber.''

Other complications showed up in a second study presented Wednesday of 19 patients.

In one case, a 24-year-old man who smoked ''crack,'' a form of cocaine, for the first time was rushed to the emergency room with paralysis of his body from the neck down, said Dr. Cyrus Mody, a fellow in clinical neurophysiology at Harbor-UCLA Medical Center in Torrance, Calif.

The man remains a quadriplegic two years later, he said. Such a complication has never before been linked to cocaine, he said.

In another case, a 43-year-old man suffered a stroke in part of the brain stem, causing severe dizziness, numbness and uncoordination on his left side, Mody said. The condition appeared after he inhaled a small amount of cocaine, his first experience with the drug, Mody said.

That man now needs a walker, he said.

Of the 19 patients, five suffered seizures and six developed such neuropsychiatric symptoms as paranoia and personality change, he said.

One patient entered a coma after using cocaine for the first time, and after recovering, he developed an uncontrollable appetite that made him gain 100 pounds in two months, Mody said. He also developed kleptomania, Mody said.

In a presentation to be given Thursday, a neurologist identifies three other cases of stroke from patients smoking crack.

A 27-year-old man developed severe headache and language disturbance while smoking crack, reports Dr. Steven Levine of Henry Ford Hospital in Detroit. In another case, a 48-year-old man who smoked two grams of crack developed headache, nausea, altered vision and speech, and failure of muscular coordinaton.

Levine also reports a 25-year-old man developed suddden headache and altered vision while smoking less than a gram of crack.