西藥中的重金屬來源主要是化學合成中的催化劑殘留， 含量控製在ppm（百萬分之幾）以下

EXECUTIVE SUMMARY
The objective of this guideline is to recommend maximum acceptable concentration limits for the
residues of metal catalysts or metal reagents that may be present in pharmaceutical substances or in
drug products. A pharmaceutical substance is defined here as a substance that is either an active
pharmaceutical ingredient or an excipient.
The metals addressed in this guideline are normally used as process catalysts or reagents during the
synthesis of pharmaceutical substances. Their use may lead to residues in the final pharmaceutical
substance, and consequently in the final drug product. Such metal residues do not provide any
therapeutic benefit to the patient and should therefore be evaluated and restricted on the foundation of
safety- and quality-based criteria. The guideline may be updated to include other metal residues in due
course.
This guideline classifies metal residues into three categories based on their individual level of safety
concern and sets concentration limits. The limits are based on the maximal daily dose, duration of
treatment, and administration route of the drug product as well as the permitted daily exposure (PDE)
of the metal residue. The guideline also includes recommendations on testing strategies, analytical
procedures and reporting levels in pharmaceutical substances or drug products.

http://www.ema.europa.eu/docs/en_GB/document_library/Scientific_guideline/2009/09/WC500003586.pdf