When you think of the FTSE 100 index, there aren’t many ‘high growth’ stocks that come to mind easily. So many of the big exciting growth companies seem to be listed in the US, leaving our key index with large, slow-burning companies such as the oil majors and healthcare giants.

However, if you’re willing to look down the list of FTSE 100 constituents and examine some of the smaller companies in the index, there are some hidden gems that have the potential to grow much faster than the average FTSE 100 stock. Here are three that I think have excellent growth potential.

Payments champion

A leader in global payments, Worldpay (LSE:WPG) floated in the UK late last year but has so far seen a rather lacklustre share price performance.

The company provides payment solutions in-store, online and through mobile devices. Given the huge movement towards online and mobile shopping over the last few years, I believe this is one of the more exciting growth areas within the FTSE 100 right now. Indeed, management plans to grow revenues between 9% and 11% per year and is targeting the US as one of its key growth markets. 

Revenue last year came in at £982m, a 14% increase on 2014. Earnings per share were a lowly 4p, however, consensus estimates have earnings at 11p and 13p over the next two years, so analysts clearly believe there’s growth on the cards.

On the current share price of 263p, earnings of 11p results mean a P/E ratio of 24, which isn’t outrageous if the company can execute its growth plans. 

Not your average pharmaceutical company

FTSE 100 pharmaceutical companies and the words ‘high growth’ are generally not seen in the same sentence together. But if you look beyond the mainstream pharmaceutical giants, there’s a lesser known drugs company that’s growing at a fast pace, Hikma Pharmaceuticals (LSE: HIK).

Hikma is a family-run company based in Jordan. With a market cap of £5.5bn, it’s a lot smaller than the big boys in the pharma space but don’t let that put you off.

The company operates three broad divisions, generic, branded and injectible medicines, and sells its products in the US, Europe and the MENA region.

Management has a strong record of delivering shareholder value through acquisitions and organic growth and the numbers speak for themselves. Over the last five years, revenues have nearly doubled, and earnings per share have risen from 52 cents in 2010 to $1.35p in 2015.

Earnings for FY2016 are estimated to fall slightly due to acquisition and integration costs, but once these issues are sorted, I expect earnings at Hikma to roar into action.

On the current P/E ratio of 26, Hikma is pricey. But given that revenues have risen at a compound annual growth rate of 14.5% over the last five years, this is a company that’s growing quickly. 

Gambling powerhouse

There may have been a few sporting upsets this year, but that shouldn’t stop newly formed Paddy Power Betfair (LSE: PPB) charging ahead.

The £7.5bn market cap gambling giant reported earnings in early May and revealed that revenues were up 16% year-on-year with particularly strong performances from online gambling.

With Euro 2016 and the Brazil Olympics on the horizon, I’m expecting the momentum to continue here, but be warned that on a P/E of 31 times next year’s earnings, this stock isn’t cheap.  

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Edward Sheldon has no position in any shares mentioned. The Motley Fool UK has recommended Hikma Pharmaceuticals and Paddy Power Betfair. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.