Catania resisted stubbornly until just before the interval, when Walter Samuel headed in from a corner.
Second-half goals by Santiago Solari, Fabio Grosso, Zlatan Ibrahimovic and Julio Cruz sealed the win to give Inter 66 points from 24 matches, 14 points ahead of second-placed AS Roma, who beat Reggina 3-0.
The ban on Catania's Massimino stadium following the death of a policeman in rioting at a Serie A match earlier this month meant the Sicilian side were forced to host Inter behind closed doors at the Manuzzi stadium in Cesena, 650 miles (1,046 km) to the north.
The empty stands seemed to affect the Italian champions more than their Sicilian rivals. The best early chance fell to Catania midfielder Fabio Caserta who fired in a swerving volley to force a fingertip save from Inter keeper Julio Cesar.
After Samuel's goal, however, Inter took control.
Solari grabbed their second goal four minutes after the restart, angling a shot in off the base of the post, and Fabio Grosso made it 3-0 with a perfect lob over Catania keeper Armando Pantanelli.
Defensive errors allowed Catania strikers Gionatha Spinesi and Giorgio Corona to score, but Inter hit back quickly on both occasions through Ibrahimovic then Cruz, to lift the team's morale after their 2-2 draw with Champions League rivals Valencia midweek.
ROMA DOMINANT
Roma were also made to work hard before finding a way past Reggina at the Olympic Stadium.
Their dominance of the game was rewarded in the 55th minute, when Francesco Totti put Francesco Tavano through alone on goal to score his first Serie A goal for the club since joining from Valencia in January.
Goals by Philippe Mexes and Christian Panucci rounded off the victory, which could have been even more convincing if Totti had not had a penalty saved six minutes from the end.
Palermo lie third on 44 points after a 1-1 draw at Atalanta on Saturday.
Lazio climbed to fourth on 37 points after first-half strikes by Sanchez Cribari and Tommaso Rocchi gave them a 2-0 win at Cagliari.
Empoli slipped to fifth after losing the Tuscan derby at Fiorentina.
Goals from Adrian Mutu and Luca Toni lifted Fiorentina to seventh on 31 points, despite the 15-point penalty handed to them after last year's match-fixing scandal, and the twice Italian champions are looking strong candidates for a European place.
In a later match, sixth-placed AC Milan (33 points) host Sampdoria (kickoff 1930 GMT).
