Irvine-based drug maker Allergan Inc. today saw its shares fall slightly after an analyst cut his 2013 profit forecast.

Allergan shares were down 1% with a market value of about $27 billion.

Seamus Fernandez of Boston investment bank Leerink Swann LLC said in a research note that he lowered his 2013 profit estimate for Allergan by some $18.2 million. Fernandez cut his forecast after CVS/Caremark Corp., the Providence, R.I.-based drugstore chain, said it would exclude Allergan’s Lumigan glaucoma drug from its formulary, or drug list.

Fernandez now expects Allergan to earn $1.46 billion in 2013. He said he doesn’t believe that the CVS/Caremark exclusion signals a bigger change among managed care companies about Allergan’s eye drug franchise.

Separately, Wells Fargo Securities said in a report that the market share of Allergan’s Botox for treating chronic migraines reached 9% in June, up from 8.7% in May. The Food and Drug Administration cleared Botox for treatment of migraines in late 2010.