Top US drugs manufacturer Pfizer yesterday reported a 20 per cent gain in fourth-quarter operating earnings, meeting Wall Street expectations, helped by sales of its blockbuster anti-cholesterol drug, Lipitor, and arthritis treatment Celebrex. Pfizer, which employs around 1,500 people in Cork and Dublin, and is also known for its anti-impotence pill Viagra, reported earnings of $1.76 billion (#1.9 billion), or 27 US cents per diluted share, excluding the impact of special items and merger-related costs.