Patent expirations have cut into sales at Big Pharma's best in recent quarters. Doom-and-gloom talk over the patent cliff ,and shaky pipelines at pharmaceutical firms, have waxed and waned, but some of the industry's best firms have kept up profitability that would make any Wall Street analyst blush.

Which firms are earning the most for your investment -- and are they really worth your money? Motley Fool contributor Dan Carroll takes a look below at the three firms maintaining the industry's best net profit margins, and explains if these stocks match up to what their businesses are bringing in.