Managerless Birmingham were up against it right from the off as Brett Pitman opened the scoring in the third minute at St Andrews, before David Edgar was shown a straight red card when he was deemed the last man, having brought down Callum Wilson.
Two goals in five first-half minutes from Wilson and Matt Ritchie effectively ended the match as a contest as the visitors led 3-0 at the interval.
Eddie Howe's men showed no remorse, though, Pugh scored twice in six second-half minutes, before Tokelo Rantie made it six from the penalty spot in the 82nd minute after David Cotterill was adjudged to have fouled Simon Francis.
Pugh rounded off his treble when he diverted home Ritchie's centre, before Rantie's second completed the demolition, leaving Birmingham - who have just one home league win in 2014 - in 23rd place.
That victory saw Bournemouth climb to fourth in the table and Wolves are another team on the up after Leon Clarke's 85th-minute goal secured a 2-1 win at Leeds United and lifted Kenny Jackett's men to third.
Derby County remain at the summit of the table despite losing 2-1 at home to Wigan Athletic, a James McClean double in the second half cancelling out a rare goal for John Eustace.
Second-placed Watford had the opportunity to usurp Derby, but they were held to a 1-1 draw by fellow high-flyers Middlesbrough at the Riverside Stadium, while Norwich City - who occupy the final play-off spot – played out a frustrating 0-0 draw at Sheffield Wednesday.
Nottingham Forest's winless league run stretched to seven matches following a disappointing 3-1 loss at home to Blackburn Rovers, the visitors benefitting from a blitz of three goals in the space of 11 minutes after the break.
Bolton Wanderers made it two wins from three matches under the stewardship of Neil Lennon. Scott Danns and a double from Mark Davies contributed to a 3-1 victory over Brentford.
Despite the win, Bolton remain in the bottom three, although they are now just two points adrift of Brighton and Hove Albion who could only muster a 1-1 draw at home to Rotherham United.
Blackpool remain at the foot of the table after losing convincingly 3-0 at Reading, while Millwall's 1-0 win over Cardiff City was their first three points in the league since August 30.
Rounding off the action, two goals from Nahki Wells saw Huddersfield Town overturn a two-goal deficit to draw 2-2 at Ipswich Town.