Drugs that should be avoided by nursing mothers are: 1. Antineoplastic drugs: Such drugs are contraindicated during lactation. However, it has also been proposed that the application of methotrexate once a week in the treatment of rheumatism is acceptable in nursing women, but the infant’s hematological parameters should be closely followed. 2. ergometrine preparations: such as bromelain and ergotamine are also contraindicated during lactation because they have the effect of inhibiting the activity of prolactin, thus reducing the secretion of milk. 3. Iodine and iodine-containing preparations: The application of such drugs is not recommended during lactation because iodine can lead to goiter and hypothyroidism in infants. Likewise, breastfeeding should be suspended when radioactive iodine is applied to treat hyperthyroidism in order to avoid exposing the infant to excessive radioactive material. 4. Alcohol consumption, smoking and drug addiction: these are all detrimental to the infant. Alcohol consumption by the mother can reduce lactation and inhibit the infant. The infant’s neurological development can also be adversely affected in the long term. Maternal smoking can lead to a higher incidence of respiratory infections and expose the infant to carcinogenic substances. Maternal drug addiction also has a negative impact on the infant, and the ability of such mothers to properly care for their infants is also a concern. 5, the application of gold agents: the application of gold agents during breastfeeding is controversial, because their levels in breast milk and the extent to which they are absorbed by the infant are not known. However, although there are no cases of adverse reactions reported in breastfed children, such drugs should be avoided during lactation. 6, oral contraceptives: oral contraceptives during breastfeeding is also controversial because of the risk of reducing lactation. 7, the application of lithium preparations: the application of lithium preparations is also controversial, because such drugs have been detected in the serum of breastfed children, however, there are many women taking such drugs without infant morbidity. Since lithium can be measured in both infant and maternal blood, recommendations for women taking lithium preparations during lactation should be treated individually. 8. Drugs acting on the central nervous system: The American Academy of Pediatrics Committee on Drugs believes that drugs acting on the central nervous system (cNs) such as antidepressants, psychostimulants, and benzodiazepines have both immediate and long-term effects on CNS function in breastfed children, so their use in nursing women is a concern. 9, other: certain drugs due to individual differences in individual cases of adverse reactions to infants. (1) mesalazine can cause diarrhea; (2) aspirin can cause metabolic acidosis; (3) carbamazepine can cause sedation, hyperexcitability and biliary hepatitis; (4) cimetidine can cause hyperexcitability and sleepiness; (5) phenobarbital can cause sedation and methemoglobinemia; (6) primidon can cause sedation and bloody diarrhea. Therefore, nursing mothers should be closely monitored when receiving these drugs.