The pharmaceutical industry tends to boast about blockbuster drugs, but it may be better off looking at blockbuster movies for inspiration. The world’s biggest drugmakers face years of stagnant growth ahead as they lose exclusive rights to their best-selling medicines, a reality likely to fuel even further consolidation, according to consultancy Bain & Co. Some industry executives see an even more drastic pruning as possible, one that would whittle the top 25 players down to six or eight massive drug companies, supported by services firms and smaller innovative players, said Tim van Biesen, head of Bain & Co’s healthcare practice.