The FTSE 100 company is one of the most popular with UK fund managers; Neil Woodford (pictured), for example, is among its biggest shareholders.
However, Miah believes that a fall in revenues has brought to light some major problems with the firm.
"The company has solely focused on branded prescription medicines," he explained.
"While this can be a successful strategy if the pipeline of drugs in R&D [research and development] makes it to the market, unfortunately this is not the case for AstraZeneca, whose late stage pipeline is wearing thin."
According to FE data, 166 funds in the IMA unit trust and OEIC universe hold the company in their top-10. Of the 102 portfolios in the UK Equity Income sector, 53 – or 52 per cent – include Astra in their top-10 holdings.
Woodford’s Invesco Perpetual Income and High Income funds both have an 8.1 per cent weighting in the company, which amounts to about £1.2bn of assets overall.
AstraZeneca has been a strong performer for the manager in the medium-term, up 45.04 per cent over five years compared with returns of 7.75 per cent from the FTSE 100.
Performance of stock vs index over 5-yrs
Source: FE Analytics
However, Miah thinks recent news flow has dealt a significant blow to the company.
Astra saw revenue fall by 21 per cent to $6.7bn in the second quarter of this year while profits tumbled by 38 per cent to $1.76bn.
Although the decline had been expected by the company due to patents expiring on key products, the impact has been exacerbated by the eurozone crisis, which has caused many governments to cut their healthcare budgets.
"Unlike some of its peers, AstraZeneca has ignored manufacturing generic drugs themselves, which is a useful insurance strategy when the pipeline looks weak and patents near expiration," Miah added.
The adviser thinks the situation is going to get worse for the firm unless it radically changes its focus.
"To counter this problem, the company has been on a cost-cutting mission; however, whilst this may help earnings in the short-term, our main concern is that without a strong pipeline, future revenues will be vulnerable," he explained.
"The company's troubles have led to the loss of the previous chief executive and it is now in the process of making a new appointment."
"As well as the fall in revenue, operating profits are down 32 per cent, earnings per share down 11 per cent and dividends paid in the quarter were roughly a third compared with the same period last year."
Miah points to GlaxoSmithKline as a better alternative for those looking for exposure to the pharmaceutical industry.
He commented: "Lack of diversification has been one of AstraZeneca's main failures and is one of the reasons why we prefer GlaxoSmithKline."
"The company is confident of its late-stage pipeline, with a potential to launch eight new drugs and vaccines in the next 24 months, which should be a material driver for organic growth."
"The yield is attractive at around 5 per cent and the growth story also looks to be improving. The business is very cash generative and is committed to using this towards increasing dividends, share buybacks and bolt-on acquisitions."
"The hoped-for improvement should be helped by new products, diversification and increasing exposure to emerging markets."
Woodford also has significant exposure to Glaxo, which has an 8.1 per cent weighting in his High Income portfolio.
A recent FE Trustnet article pointed to the high degree of dividend risk in UK Equity Income funds, with some – including Woodford’s portfolios – relying on a single company to deliver more than 10 per cent of their overall income.