Patients with a risk of blood clotting who take the Sanofi Aventis drug Clexane were advised by the Health Ministry on Wednesday night to continue to take it even though some batches are contaminated with "low levels" of an impurity called over-sulfated chondroitin sulphate (OSCS). There have been some reports of serious allergic reactions and a number of deaths in some patients to the batches, which were sent to 13 countries in North America and Europe as well as Israel. Government pharmaceutical agencies abroad issued an alert about the Clexane pre-filled syringes, even though they have stressed that there is currently no evidence that this is associated with any risk to patients. No more batches manufactured since April 1 have been affected, according to international reports. The US Food and Drug Administration has said in recent weeks that Chinese-made ingredients for the blood-thinning drug may have been deliberately contaminated. Chinese officials have admitted that the contaminant was present in some batches, and acknowledged the presence of the contaminant, which is synthetic. Clexane is the commercial name for a type of low-molecular heparin. The Health Ministry in Jerusalem said there has been no proof of a direct connection between the impurity and the reactions. Levels of OSCS are monitored by the ministry in all batches. The ministry decided to allow controlled use of Clexane "to prevent a shortage" on the Israeli market. Patients prescribed Clexane should continue taking it under their doctors' supervision. Any side effects should be reported to the ministry. Injection directly into a vein or artery should be avoided in the meantime, unless the doctor insists that this method is needed; in such a case, the doctor should give ongoing support and supervision.