Cigna had negotiated a price of $1.75 for the Amlodipine prescription, according to the suit. The pharmacy, by agreement, was permitted to keep $1.75 of the $20 co-payment and obligated to return the remaining $18.25, known as "the spread," to the insurer. The suit claims the delivery of the spread to the insurer is known in the industry as a "clawback."