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This general chapter specifies limits for the amounts of elemental impurities in drug products. Elemental impurities include catalysts and environmental contaminants that may be present in drug substances, excipients, or drug products. These impurities may occur naturally, be added intentionally, or be introduced inadvertently (e.g., by interactions with processing equipment and the container closure system).2S (USP38) When elemental impurities are known to be present, have been added, or have the potential for introduction, assurance of compliance to the specified levels is required. A risk-based control strategy may be appropriate when analysts determine how to assure compliance with this standard. Due to the ubiquitous nature of arsenic, cadmium, lead, and mercury, they (at the minimum) must be considered in the risk assessment.2S (USP38) Regardless of the approach used, compliance with the limits specified is required for all drug products unless otherwise specified in an individual monograph or excluded in paragraph three of this introduction.
The drug products containing purified proteins and polypeptides (including proteins and polypeptides produced from recombinant or non-recombinant origins), their derivatives, and products of which they are components (e.g., conjugates) are within the scope of this chapter, as are drug products containing synthetically produced polypeptides, polynucleotides, and oligosaccharides.
This chapter does not apply to radiopharmaceuticals, vaccines, cell metabolites, DNA products, allergenic extracts, cells, whole blood, cellular blood components or blood derivatives including plasma and plasma derivatives, dialysate solutions not intended for systemic circulation, and elements that are intentionally included in the drug product for therapeutic benefit. This chapter does not apply to products based on genes (gene therapy), cells (cell therapy), and tissue (tissue engineering).2S (USP38)
The limits presented in this chapter do not apply to excipients and drug substances, except where specified in this chapter or in the individual monograph. However, elemental impurity levels present in drug substances and excipients must be known, documented, and made available upon request.
This chapter does not apply to2S (USP38) articles intended only for veterinary use. Requirements listed in this chapter also do not apply to total parenteral nutritions (TPNs) and dialysates.2S (USP38) Dietary supplements and their ingredients are addressed in Elemental Contaminants in Dietary Supplements 2232.

The determination of the oxidation state, organic complex, or combination is termed speciation. Each of the elemental impurities has the potential to be present in differing oxidation or complexation states. However, arsenic and mercury are of particular concern because of the differing toxicities of their inorganic and complexed organic forms.
The arsenic limits are based on the inorganic (most toxic) form. Arsenic can be measured using a total-arsenic procedure under the assumption that all arsenic contained in the material under test is in the inorganic form. Where the limit is exceeded using a total-arsenic procedure, it may be possible to show via a procedure that quantifies the different forms that the inorganic form meets the specification.
The mercury limits are based upon the inorganic (2+) oxidation state. The methyl mercury form (most toxic) is rarely an issue for pharmaceuticals. Thus, the limit was established assuming the most common (mercuric) inorganic form. Limits for articles that have the potential to contain methyl mercury (e.g., materials derived from fish) are to be provided in the monograph.
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The toxicity of an elemental impurity is related to its extent of exposure (bioavailability). The extent of exposure has been determined for each of the elemental impurities of interest for three routes of administration: oral, parenteral, and inhalational. These limits are based on chronic exposure. Consider the oral permissible daily exposures (PDEs) in Table 1, as a starting point in developing specific PDEs for other routes of administration except where otherwise stated in the individual monograph.2S (USP38) [NoteThe routes of administration of drug products are defined in Pharmaceutical Dosage Forms 1151. ]
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The limits described in the second through fourth columns of Table 1 are the base daily dose PDEs of the elemental impurities of interest for a drug product taken by a2S (USP38) patient according to indicated routes of administration. 2S (USP38)
Parenteral Products
Parenteral drug products with maximum daily volumes up to 2 L may use the maximum daily volume to calculate permissible concentrations from PDEs. For products whose daily volumes, as specified by labeling and/or established by clinical practice, may exceed 2 L (e.g., saline, dextrose, TPNs, solutions for irrigation), a 2-L volume may be used to calculate permissible concentrations from PDEs.2S (USP38)
Table 1. Elemental Impurities for Drug Products
Element Oral Daily
Dose PDEa
Parenteral Daily
Dose PDE
Inhalational Daily
Dose PDE
2S (USP38)
Cadmium 5 2 22S (USP38) 2S (USP38)
Lead 5 5 52S (USP38) 2S (USP38)
Inorganic arsenic a 15 15 22S (USP38) 2S (USP38)
Inorganic mercury a 30 3 12S (USP38) 2S (USP38)
Iridium 100 10 12S (USP38) 2S (USP38)
Osmium 100 10 12S (USP38) 2S (USP38)
Palladium 100 10 12S (USP38) 2S (USP38)
Platinum 100 10 12S (USP38) 2S (USP38)
Rhodium 100 10 12S (USP38) 2S (USP38)
Ruthenium 100 10 12S (USP38) 2S (USP38)
Chromium 11000 1100 32S (USP38) 2S (USP38)
Molybdenum 3000 1500 102S (USP38) 2S (USP38)
Nickel 200 20 52S (USP38) 2S (USP38)
Vanadium 100 10 12S (USP38) 2S (USP38)
Copper 3000 300 302S (USP38) 2S (USP38)
a   See Speciation section.2S (USP38)
Options for Demonstrating Compliance
drug product analysis option
The results obtained from the analysis of a typical dosage unit, scaled to a maximum daily dose, are compared to the Daily Dose PDE.
Daily Dose PDE measured value (µg/g) × maximum daily dose (g/day)
The measured amount of each impurity is NMT the Daily Dose PDE, unless otherwise stated in the individual monograph.
summation option
Separately add the amounts of each elemental impurity (in µg/g) present in each of the components of the drug product:
Daily Dose PDE [SM1(CM × WM)] × DD

M = each ingredient used to manufacture a dosage unit
CM = element concentration in component (drug substance or excipient) (µg/g)
WM = weight of component in a dosage unit (g/dosage unit)
DD = number of units in the maximum daily dose (unit/day)
The result of the summation of each impurity is NMT the Daily Dose PDE, unless otherwise stated in the individual monograph. Before products can be evaluated using this option, the manufacturer must ensure that additional elemental impurities cannot be inadvertently added through the manufacturing process or via the container closure system over the shelf life of the product.
individual component option
For drug products with a daily dose of NMT 10 g, if all drug substances and excipients in a formulation meet the concentration limits shown in Table 2, then these components may be used in any proportion. No further calculation is necessary. While elemental impurities derived from the manufacturing process or the container closure system are not specifically provided for in the Individual Component Option, it is expected that the drug product manufacturer will ensure that these sources do not contribute significantly to the total content of elemental impurities.2S (USP38)
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The concentration2S (USP38) of elemental impurities in drug substances and excipients must be controlled and, where present, documented.2S (USP38) The acceptable levels for these impurities depend on the material's ultimate use. Therefore, drug product manufacturers must determine the acceptable level of elemental impurities in the drug substances and excipients used to produce their products.
The values provided in Table 2 are example2S (USP38) concentration limits for components (drug substances and excipients) of drug products dosed at a maximum daily dose of 2S (USP38) 10 g/day. These values serve as default concentration limits to aid discussions between drug product manufacturers and the suppliers of the components of their drug products. [NoteIndividual components may need to be limited at levels different from those in the table depending on monograph-specific mitigating factors. ]
Table 2. Example Concentration Limits for Components of Drug Products with a 10-g Maximum Daily Dose2S (USP38)
Element Concentration Limits (g/g) for Components Used in Oral Drug Products Concentration Limits (g/g) for Components Used in
Parenteral Drug Products
Concentration Limits (g/g) for Components Used in
Inhalation Drug Products2S (USP38)
Cadmium 0.5 0.2 0.22S (USP38)
Lead 0.5 0.5 0.5
Inorganic arsenic a 1.5 1.5 0.22S (USP38)
Inorganic mercury a 3 0.3 0.12S (USP38)
Iridium 10 1 0.12S (USP38)
Osmium 10 1 0.12S (USP38)
Palladium 10 1 0.12S (USP38)
Platinum 10 1 0.12S (USP38)
Rhodium 10 1 0.12S (USP38)
Ruthenium 10 1 0.12S (USP38)
Chromium 1100 110 0.32S (USP38)
Molybdenum 300 150 12S (USP38)
Nickel 20 2 0.52S (USP38)
Vanadium 10 1 0.12S (USP38)
Copper 300 30 32S (USP38)
a  See Speciation section.2S (USP38)
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If, by process monitoring and supply-chain control, manufacturers can demonstrate compliance,2S (USP38) then further testing may2S (USP38) not be needed. When testing is done to demonstrate compliance, proceed as directed in Elemental Impurities—Procedures 233 and minimally include arsenic, cadmium, lead, and mercury in the Target Elements evaluation.
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(GCCA2010) General Chapters - Chemical Analysis
USP38–NF33 Page 243
USP38–NF33 Supplement : No. 2 Page 7594
Pharmacopeial Forum: Volume No. 40(2)