Today I’m looking at the investment prospects of three recent FTSE risers.

Medicines giant on the march

Pharmaceuticals ace AstraZeneca (LSE: AZN) saw its share price enjoy a solid 3% bump between last Monday and Friday and I believe further gains could be on the horizon. Not only does the essential role of medicines make the firm a strong ‘defensive’ contender (a critical quality in the current investing climate) but I believe the prospect of further positive regulatory news should keep the stock price rising.

Investors should be aware that AstraZeneca isn’t likely to generate breakneck earnings growth any time soon however, as crippling patent losses like those of Crestor and Nexium keep sales on the back foot. Indeed, the City expects the drugs play to follow a predicted 6% earnings slip in 2015 with a similar drop this year.

Still, I reckon a P/E rating of 16.8 times is a decent point at which to buy, as AstraZeneca’s rejuvenated R&D operations — combined with stunning healthcare investment across the world — is likely to drive profits through the roof in the years ahead.

Throw in a projected dividend of 280 cents, a figure that yields a terrific 4.2%, and I believe AstraZeneca is a very canny investment.

Gold play goes forth

I’m far from positive concerning the growth outlook at Randgold Resources (LSE: RRS) however, thanks to the uncertain outlook over metal prices currently.

Randgold Resources saw its stock value gain 4% between Monday and Friday, helped by a slight sagging of the US dollar and a relief rally across global stock and commodity markets. But as investor sentiment continues to sway back and forth, I don’t believe stockpickers should put much faith in this mini rally holding up for the mining and energy spaces.

Sure, Randgold Resources may be steadily hiking output to offset falling gold prices. But safe-haven demand for gold is barely holding the price above $1,000 per ounce. And the prospect of fresh dollar strength, allied with falling bar and jewellery demand from Asia, could send values below this critical marker.

The City expects Randgold Resources to punch a 21% earnings rise in 2016, creating an elevated P/E multiple of 27.2 times. Given the company’s high risk profile, I don’t believe the company merits serious consideration at current stock prices, however.

Producer receives fresh fuel

Oil giant Tullow Oil (LSE: TLW) also surged last week as Brent values steadily recovered ground. After toppling to fresh 13-year troughs on Wednesday at $27.20 per barrel, ‘black gold’ prices bounced back to finish the week around the $32 mark.

This ascent consequently drove Tullow Oil’s share value 14% higher between Monday and Friday. But I believe the crude market remains too fragile to realistically expect further price gains — just last week Iraq announced that production is rattling along at record levels, adding to fresh waves of supply hitting the market from fellow OPEC member Iran.

When you also factor-in insipid global demand growth, not to mention the potential for further US dollar strength, I believe Tullow Oil could see its share price dive again.

Broker consensus suggests the producer will improve earnings from 1.5 US cents per share in 2015 to 14.2 cents in 2016 as output from its TEN asset kicks-in. But with Tullow Oil sporting a subsequent P/E multiple of 24.8 times, like Randgold Resources I believe the risks outweigh the potential rewards at current prices.

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Royston Wild has no position in any shares mentioned. The Motley Fool UK has recommended AstraZeneca and Tullow Oil. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.