Non-steroidal Anti-inflammatories – which is the odd one out?

(a)        Diclofenac                    P.N.     ______________________

(b)        Metronidazole              P.N.     ______________________

(c)        Piroxicam                     G.N.    ______________________

(e)               Ibuprofen                     P.N.     ______________________