Hikma shares rose by as much as 9.4% in their largest one-day increase since last September.
Pfizer is the largest supplier in the U.S. injectables market and Hikma is the second-largest, analysts said.
Hikma, which has a market value of around $5.6 billion compared with Pfizer's $205.7 billion, might struggle to meet demand, Herrmann said.
European healthcare stocks (.SXDP) were up around 0.7% on the day, outperforming the broader STOXX 600 (.STOXX), which rose 0.4%.
Pfizer shares were up 0.16% in premarket trading.
Persons:
Fresenius, Max Herrmann, Herrmann, Hikma, Amanda Cooper, Jan Harvey
Organizations:
Pfizer, Reuters, Thomson
Locations:
U.S, Rocky Mount, North Carolina, Hikma