* Swine flu, other one-offs to boost first-quarter earnings
* Glaxo Q1 EPS seen rising 12 pct, Astra up 8 pct
* Glaxo results April 28 1100 GMT, Astra April 29 1000 GMT
LONDON, April 23 (Reuters) - Britain's leading drugmakers, GlaxoSmithKlineand AstraZeneca , should report healthy quarterly results next week, helped by swine flu and other one-offs -- but the rest of the year will be more tricky.
Glaxo stands to book a second quarter of exceptional vaccine sales in the three months to March, buoyed by demand for shots against the H1N1 pandemic.
Despite some governments cutting back or cancelling orders, it is likely to rake in around 500 million pounds ($773 million) in swine flu revenue, although analyst estimates range widely from just over 300 million pounds up to 700 million.
The H1N1 boom, however, is not expected to last beyond the first quarter, given the seasonal nature of vaccination and the decline in swine flu cases.
For AstraZeneca, the bonanza has already run its course and analysts forecast little, if any, revenue from its nasal spray H1N1 swine flu vaccine in the first quarter.
Instead, the Anglo-Swedish group, which reports in dollars, will enjoy something of a currency boost as well as a tax bonus, following settlement of a tax row with British authorities that will reduce its tax rate. [ID:nLDE61M09R]
The result should be a 12 percent rise in first-quarter earnings per share at Glaxo and around 8 percent for AstraZeneca, according to consensus forecasts.
The remainder of the year promises to be much tougher across the sector, due to intensified generic competition and pressure from healthcare reform, not just in the United States but also Japan and Germany, according to analysts at Deutsche Bank.
Glaxo faces accelerating erosion of sales of antiviral Valtrex as the year progresses, while Astra will see a growing impact from generic copies of heart drug Toprol XL.
U.S. drugmakers Eli Lillyand Johnson & Johnson have already warned that President Barack Obama's healthcare reforms will slice into profits this year.
Swiss drugmakers Novartisand Roche , both of which reported strong quarterly numbers, have been more sanguine over the impact of U.S. market changes.
Investors will be watching keenly for comments on the U.S. market from both British players. AstraZeneca, however, seems unlikely to change its 2010 outlook since it already said it anticipated the impact of healthcare reform when it gave original 2010 guidance in January.
Glaxo does not forecast its earnings.
The following table shows consensus earnings per share and sales forecasts, as compiled by Thomson Reuters I/B/E/S:
Q1 EPS* YEAR AGO Q1 SALES YEAR AGO GlaxoSmithKline 29.4p 26.3p 7.12 bln stg 6.77 bln AstraZeneca $1.70 $1.58 $8.19 bln $7.70 bln
* Figures are for "before major restructuring" and "core" earnings
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