Interactions with Dietary Supplements

Minerals
Calcium, magnesium, and potassium depletion requiring prolonged replacement were reported in a child with tetany who had just completed a three-week course of i.v. tobramycin.¹ The authors suggest this may have been due to kidney damage related to the drug. Seventeen patients with cancer developed calcium, magnesium, and potassium depletion after treatment with aminoglycoside antibiotics, including tobramycin.² The authors suggested a possible potentiating action of tobramycin-induced mineral depletion by chemotherapy drugs, especially doxorubicin (Adriamycin®).

Until more is known, people receiving i.v. tobramycin should ask their doctor about monitoring calcium, magnesium, and potassium levels and the possibility of mineral replacement.

Probiotics
A common side effect of antibiotics is diarrhoea, which may be caused by the elimination of beneficial bacteria normally found in the colon. Controlled studies have shown that taking probiotic microorganisms—such as Lactobacillus casei, Lactobacillus acidophilus, Bifidobacterium longum, or Saccharomyces boulardii—helps prevent antibiotic-induced diarrhoea.³

The diarrhoea experienced by some people who take antibiotics also might be due to an overgrowth of the bacterium Clostridium difficile, which causes a disease known as pseudomembranous colitis. Controlled studies have shown that supplementation with harmless yeast—such as Saccharomyces boulardii⁴ or Saccharomyces cerevisiae (baker’s or brewer’s yeast)⁵ —helps prevent recurrence of this infection. In one study, taking 500 mg of Saccharomyces boulardii twice daily enhanced the effectiveness of the antibiotic vancomycin in preventing recurrent clostridium infection.⁶ Therefore, people taking antibiotics who later develop diarrhoea might benefit from supplementing with saccharomyces organisms.

Treatment with antibiotics also commonly leads to an overgrowth of yeast (Candida albicans) in the vagina (candida vaginitis) and the intestines (sometimes referred to as “dysbiosis”). Controlled studies have shown that Lactobacillus acidophilus might prevent candida vaginitis.⁷

Vitamin K
A few cases of excessive bleeding have been reported in people who take antibiotics.^{8 9 10 11} This side effect may be the result of reduced vitamin K activity and/or reduced vitamin K production by bacteria in the colon. One study showed that people who had taken broad-spectrum antibiotics had lower liver concentrations of vitamin K2 (menaquinone), though vitamin K1 (phylloquinone) levels remained normal.¹² A few antibiotics appear to exert a strong effect on vitamin K activity, while others may not have any effect. Therefore, one should refer to a specific antibiotic for information on whether it interacts with vitamin K. Doctors of natural medicine sometimes recommend vitamin K supplementation to people taking antibiotics. Additional research is needed to determine whether the amount of vitamin K1 found in some multivitamins is sufficient to prevent antibiotic-induced bleeding. Moreover, most multivitamins do not contain vitamin K.

As with many antibiotics, tobramycin can deplete vitamin K.^{13 14} It makes sense for people taking tobramycin to supplement vitamin K to protect against drug-induced deficiency. Doctors sometimes suggest a daily intake between a few hundred micrograms and one milligram.