Merck & Co has suffered another tough quarter, hit by charges, unfavourable exchange rates and patent expiries on its asthma/allergic rhinitis blockbuster Singulair.

Net income came in at $906 million, down from $1.79 billion in the second quarter last year, while turnover declined 11% to $11.01 billion. Singulair (montelukast) sank 80% to $281 million following patent expiry in the main European markets in February 2013, having gone generic in August 2012 in the USA.

The company's best-selling drug is the diabetes drug Januvia (sitagliptin) which generated $1.07 billion, up just 1%, though Janumet (sitagliptin plus metformin) brought in $474 million, a rise of 16%. Turnover from the HIV drug Isentress (raltegravir) reached $412 million, up 4%, while sales of the cervical cancer vaccine Gardasil climbed 18% to $383 million.

The cholesterol drugs Vytorin (ezetimibe plus simvastatin) and Zetia (ezetimibe) reached $417 million and $650 million, down 6% and up 3% respectively. The anti-inflammatory Remicade (infliximab), the Johnson & Johnson drug which Merck sells outside the USA, contributed $5 27, up 2%.

Chief executive Kenneth Frazier (pictured) said that “with seven of our top 10 products growing in the second quarter and solid performance overall, we continue to navigate significant patent expiries and adapt to the evolving global healthcare environment". In terms of pipeline, he made special mention of the firm's investigational PD-1 antibody lambrolizumab, adding that Merck continues to manage its costs effectively.