On 18 October Pfizer announced that it would withdraw the first inhaled insulin, Exubera, from the market, as sales were too low. In January 2006 Pfizer bought the worldwide rights to Exubera from Sanofi-Aventis for $1.3bn (£0.6bn; €0.9bn), and in August 2006 the product was introduced in Britain. In the first nine months of 2007, worldwide sales of Exubera amounted to $12m, rather short of its projected $2bn blockbuster status. Instead it will cost Pfizer an estimated $2.8bn to “write it off.”

So why were sales of Exubera so far below expectations? Was it that:

• Labelling and national guidance were too restrictive?

• Pfizer did not persist long enough for the market to open up?

• The cost was too high?

• The inhalation device was less convenient than anticipated?

• The dose equivalence was confusing or inaccurate?

• Doubts lingered over its long term safety?

• Inhaled insulin is suitable for meal bolus insulin but not basal insulin doses?

• Temporary cough can be irritating?

• None, some, or all of the above?

Exubera's withdrawal has implications for the companies that make the insulin and the inhalers, as well as Nektar Therapeutics, which developed the inhaler and retains a stake in the product. …