The absorption of
hydrochlorothiazide and
chlorothiazide can be reduced by more
than one-third if colestipol is given concurrently.
Colestyramine also reduces the absorption of
hydrochlorothiazide by more than two-thirds.
Separating the dosages of
hydrochlorothiazide and
colestyramine by 4 hours can reduce, but not totally overcome the effects of this interaction. It may therefore be prudent to ensure a 6-hour separation.