Amoxicillin & Caffeine

Drugs can have interactions with other drugs, as well as certain foods and other substances. Although most of the interactions you hear about are adverse in character, sometimes the reverse can be true. Such is the case with amoxicillin, a penicillin-based antibiotic, and caffeine, a central nervous system stimulant 1. A 2008 study shows that the two have a synergistic effect on at least one widely occurring bacterium, a so-called bad germ that causes a wide array of illnesses.

Is This an Emergency?

If you are experiencing serious medical symptoms, seek emergency treatment immediately.


Amoxicillin belongs to a class of drugs known as penicillin-like antibiotics, according to MedlinePlus 1. As is the case with all antibiotics, this drug is ineffective against viral illnesses such as colds and influenza. Available in capsule, tablet, liquid and pediatric drops, amoxicillin is usually taken every 12 hours or every eight hours 1. If you have experienced any allergic-type reaction to penicillin-based drugs, let your doctor know so that he can prescribe another form of antibiotic medication.


It is a naturally occurring alkaloid that is found in the fruit, leaves and seeds of more than 60 plants worldwide, according to the European Food Information Council. However, scientists consider caffeine a psychoactive substance that acts as a stimulant on the central nervous system. If you ever had difficulty falling asleep after a late-night cup -- or two -- of coffee, you know firsthand the stimulant effects of caffeine.

Nigerian Study

A team of Nigerian pharmaceutical researchers conducted an in-vitro study to determine what, if any, effect caffeine had on the efficacy of three penicillin-based antibiotics in halting the growth of the Staphylococcus aureus bacterium 3. The Centers for Disease Control and Prevention estimates that roughly 30 percent of all people carry this staph germ in their noses and on their skin 2. Most of the time, the germ causes no problem, but under certain circumstances it can cause:

  • serious infections
  • including pneumonia
  • endocarditis
  • osteomyelitis
  • bacteremia
  • sepsis

The Nigerian researchers found that caffeine potentiated the effects of amoxicillin against this strain of Staphylococcus 1. In an article in the June 2008 issue of the “Tropical Journal of Pharmaceutical Research,” they reported that caffeine sharply decreased the minimum inhibitory concentration, or MIC, of amoxicillin in fighting this strain of staph 1. MIC specifies the minimum amount of a drug needed to halt the visible growth of a microbe during in-vitro study. The other drugs tested, ampicillin and benzylpenicillin, had little or negative MIC changes when used with caffeine.

Implications of Study

The Nigerian study indicates that co-administration of caffeine and amoxicillin might help fight Staphylococcus aureus infections more effectively 1. However, human testing will be needed to confirm this finding. It’s also important to note that although amoxicillin can be used to fight other forms of bacteria, this test only indicates that its use with caffeine is effective against this particular strain of Staphylococcus 1.