Pharmaexposure

Milk and dairy products

The absorption of most tetracyclines is markedly reduced by milk and other dairy products. Reduction is reported at up to 65%.
Doxycyline and minocycline are less affected by this food group although a reduced absorption of 25-30% is reported.
Dairy products also reduce the bioavailability of ciprofloxacin and norfloxacin.
As a consequence, it is usual to recommend that tetracyclines and quinolones are taken one hour before food or 2 hours after food to avoid an interaction with all forms of dairy calcium.
In the case of strontium, the manufacturer remarks that food, milk and dairy products reduce the bioavailability of strontium by 60 to 70% when compared to bioavailability following administration 3 hours after a meal. For this reason recommendations state that strontium should be taken at bedtime at least 2 hours after eating.


Caffeine
Caffeine is a methylxanthine derivative that is contained in tea, coffee, chocolate,and beverages and in compound analgesic preparations. Caffeine is a proven ergogenic aid, increasing athletic performance, endurance, and mental chronometry even at very low doses.
As a consequence of this it is likely that caffeine-containing products will reduce the efficacy of hypnotics and increase the risk of insomnia.
Patients on antiarrythmics should also avoid excessive caffeine because of the risk of tachycardias.
Theophylline, which is chemically related to caffeine and licensed for the prophylaxis and treatment of reversible bronchospasm associated with asthma and chronic obstructive pulmonary disease, is a xanthinederivative.
Thus the concurrent consumption of other xanthine-containing products is contraindicated.