The bears have taken full control of the S&P/ASX 200 (Index: ^AXJO) (ASX:XJO) this afternoon with the main index falling 1.8% to 5,354 points.

The selling has been pretty indiscriminate with every sector, except for gold, trading firmly in negative territory.

These four shares have been hit particularly hard today:

Sirtex Medical Limited (ASX: SRX)

Shares of Sirtex have fallen more than 5% today, despite it providing an upbeat earnings outlook at its AGM yesterday. Although the company expects to deliver another year of double-digit dose sales growth, it appears some investors may be disappointed with management’s guidance for an increased level of investment in sales and marketing necessary to achieve this. Furthermore, some investors may be waiting on the sidelines until the results from a number of key clinical trials are released later next year.

IPH Ltd (ASX: IPH)

IPH was one of the best performing shares yesterday, but the tables have turned today, with the shares falling more than 4.1% to $5.52. Interestingly, the company today announced the $27 million acquisition of Ella Cheong (Hong Kong), an intellectual property firm that specialises in providing services throughout China and Asia. IPH expects the deal to be earnings per share accretive and will be funded via a mix of shares and cash.

Mcgrath Ltd (ASX: MEA)

Shares of McGrath have dived more than 7% today following the release of better-than-expected inflation figures. The chance of further interest rate cuts this year (and perhaps next year) looks less likely following the release of the data and this could be seen as potentially having a slowing impact on the broader housing market. Today’s disappointing move means McGrath shares are now trading more than 54% below their December 2015 IPO price of $2.10.

ResMed Inc. (CHESS) (ASX: RMD)

Shares of ResMed have slumped more than 3.5% today, despite it reporting an encouraging first quarter result. Adjusted revenue and income increased by 5% and 4%, respectively, although it appears some investors may have been disappointed with the jump in administrative costs and research and development spending during the quarter. Nevertheless, the company’s recent acquisition of Brightree appears to be making a meaningful contribution to growth in sales and helping with margin expansion.

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Motley Fool contributor Christopher Georges owns shares of IPH Ltd and Sirtex Medical Limited. The Motley Fool Australia owns shares of IPH Ltd. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy. This article contains general investment advice only (under AFSL 400691). Authorised by Bruce Jackson.