When my DD was on formula she was having Karicare Lactose Free formula with thickener added to stop her from chucking. It used to take her ages to finish her bottle so I changed teats to Pidgeon Y shaped ones - they are the sime size as the Avent teats so fit a wide neck bottle. This allowed the formula to flow easier for her and she started drinking faster.

I also found that once she was on the thickened formula - which AR is - she really cut down on the amounts of feeds she was having as it took longer to digest plus having the thickener had extra calories as well. By the time she was 4 months old she was down to 4 feeds a day and by 6 months she was on 3 feeds a day, although by the time she was 4 months she was also starting to eat solids.