AIRCRAFT STOPPED CLIMB AT FL80 DUE PRESSURIZATION INDICATION BUT LATER REQUESTED CLIMB AND REPORTED THAT ISSUE RESOLVED. AIRCRAFT WAS GIVEN CLIMB TO FL360. WHILE CROSSING FL230 APPROXIMATELY, BOTH CAPTAIN AND FIRST OFFICER FELT DIZZY AND DROWSY WITH A FEELING OF NOT BEING ACTIVE. IMMEDIATELY, BOTH THE CREW MEMBERS USED OXYGEN MASKS. LCC WAS FAINTED AND GAINED CONSCIOUSNESS AFTER ADMINISTRATION OF OXYGEN. OTHER CABIN CREW WAS ALSO NOT FEELING COMFORTABLE. AT TIME 241924LT POSITION 100 NM FROM LAHORE AT FL270 AIRCRAFT REQUESTED DESCEND AND DIVERSION BACK TO LAHORE DUE PRESSURIZATION PROBLEM. AIRCRAFT LANDED SAFELY AT 241951LT.
