From the Guidelines
Milk does interact with tetracycline, but the interaction is more related to the absorption of tetracycline in the gastrointestinal tract rather than a direct interaction in breast milk. When considering the use of tetracycline in lactating mothers, it's essential to note that tetracyclines are present in very low levels in breast milk, and the calcium in breast milk might inhibit absorption by infants 1. The peak breast milk concentration of tetracycline is only 2.58 mg/L, and it is undetectable in the serum of breastfeeding infants 1. However, when taking tetracycline orally, it is recommended to avoid consuming milk or other dairy products, calcium supplements, antacids, or foods high in calcium, iron, magnesium, or aluminum, as these can bind to tetracyclines and reduce their absorption by up to 50-90% 1. Some key points to consider when using tetracycline include:
- Tetracycline should only be prescribed for short-term use with avoidance of repeated courses 1.
- Doxycycline is now considered acceptable for short-term use even in children aged <8 years, and because of the low concentrations of all tetracyclines found in breast milk, significant adverse reactions are unlikely 1.
- Minocycline has been associated with black discoloration of breast milk believed to be caused by iron pigment deposition in macrophages, although this is not likely to pose a risk for mothers or infants 1. It's crucial to follow the recommended dosage and administration guidelines for tetracycline to ensure its effectiveness and minimize potential interactions with milk or other substances.
From the FDA Drug Label
that the absorption of tetracyclines is reduced when taken with foods, especially those which contain calcium. However, the absorption of doxycycline is not markedly influenced by simultaneous ingestion of food or milk. Food and some dairy products also interfere with absorption.
The absorption of tetracycline is reduced when taken with milk or dairy products, but the absorption of doxycycline is not markedly influenced by simultaneous ingestion of milk.
- Tetracycline and milk interaction: yes, absorption is reduced
- Doxycycline and milk interaction: no, absorption is not markedly influenced 2 3
From the Research
Interaction between Milk and Tetracycline
- Milk and other dairy products can interfere with the absorption of tetracycline derivatives by 50 to 90% or even more, due to the formation of chelates with polyvalent metallic cations such as Ca++ 4.
- The presence of calcium in milk can severely impair the absorption of tetracycline, even in small volumes 5.
- Tetracyclines have a high affinity to form chelates with polyvalent metallic cations, which can reduce their absorption in the gastrointestinal tract 4.
Mechanism of Interaction
- The formation of tetracycline-metal complexes can reduce the absorption of tetracyclines, and the severity of the interaction depends on the nature of the tetracycline derivative, the cation, and the doses used 4.
- Tetracyclines can bind to calcium and other divalent cations, which can affect their bioavailability and activity 6, 7.
- The interaction between tetracyclines and calcium can also affect the function of osteoclasts and the regulation of cytosolic calcium concentration 6.
Clinical Significance
- The interaction between milk and tetracycline can be clinically significant in cases where the infecting pathogens are moderately resistant to tetracyclines and relatively high serum concentrations are needed for proper bacteriostasis 4.
- To minimize the interaction, an interval of 3 hours between the ingestion of tetracyclines and cations is recommended 4.