Complex sentence: This effect manifests first as a fall in hemoglobin levels, occurs quite predictably once a cumulative dose of 20 g has been given, is fully reversible once the drug is stopped, and does not predict future development of aplastic anaemia.
Split into simpler sentences: This effect manifests first as a fall in hemoglobin levels which occurs quite predictably once a cumulative dose of 20 g has been given. The anaemia is fully reversible once the drug is stopped and does not predict future development of aplastic anaemia.