South African Afrox expects basic earnings for the half-year to March to fall by between 257 and 274 cents from the year-ago period.
The company said: 'The reason for the decline in basic earnings per share is that the exceptional surplus in the previous corresponding period will not be repeated.'
According to Reuters headline earnings per share (EPS) - the key measure of profit in South Africa which strips out capital, non-trading and certain extraordinary items - will not be impacted by the exceptional surplus.
Afrox did not say what had caused the surplus.
In the previous period, Afrox sold its stake in Afrox Healthcare to a group of black investors for 3.4 billion rand, the company said at the time.
The company posted a 12 per cent rise in first-half headline EPS to 100.8 cents for the corresponding half-year period last year.