Darren Bravo (26) and Marlon Samuels (four) were at the crease with West Indies needing another 251 runs while Pakistan need eight wickets to take a 1-0 lead in the three-match series.
Leg-spinner Devendar Bishoo took a career best 8-49 to dismiss Pakistan for a paltry 123 in their second innings on a day when 16 wickets fell.
Earlier Yasir Shah took 5-121 to dismiss West Indies for 357 in their first innings, also becoming the second-joint fastest to complete 100 wickets in Test cricket.
The second Test will be played in Abu Dhabi (October 21-25) and the third in Sharjah (October 30-November 3).