Unclear exactly what country you are studying in or what your goal is. In the UK the usual pre-reg pharmacy course is the MPharm. You could do it as a second degree after a BSc in Pharmacology but you'd need to start from the beginning so there's little point in doing the pharmacology course beforehand unless you changed your mind after originally deciding against pharmacology.
If you want to become a dispensing pharmacist though a pharmacology degree doesn't do anything to progress you to that goal in the UK.
In other countries such as the US where the pre-reg pharmacy course may be a postgraduate degree then a pharmacology undergraduate is probably a fine first degree.