Pharmacology assay codes Codes for pharmacology assays. Pharmacology analyte codes This section lists the codes for pharmacology (PK) drug analyte codes available in LDMS. Pharmacology system censor codes This section lists the pharmacology (PK) system censor codes available in LDMS. Pharmacology assay user censor codes This section lists the pharmacology assay user censor codes available in LDMS. Pharmacology concentration units These unit codes are used for PK specimen concentration values.