• Other antibiotics. Several antibiotics are sometimes used by physicians to treat certain infections, but the use of multiple antibiotics also increases the risk of side effects.

  • Anticoagulants. Medications that prevent the formation of blood clots. Some antibiotics may increase the effect of anticoagulants.

  • Nonsteroidal anti-inflammatory drugs (NSAIDs). Medications that reduce pain and inflammation by inhibiting the production of certain chemicals in the body. Some antibiotics may increase the incidence or severity of side effects from NSAIDs.

  • Antiviral medications. Some antibiotics may decrease the effect of these virus–fighting medications.

  • Diarrhea medications. These may increase the effects of some antibiotics.

  • Calcium supplements. These may decrease the effectiveness of some antibiotics.

  • Oral contraceptives. Medications that inhibit the reproductive cycle of women and prevent pregnancy. Antibiotics can lessen the effectiveness of birth control pills.

  • Bronchodilators. Medications that widen airway passages in the lungs and are often used in the treatment of asthma. Some antibiotics may increase the concentration of some bronchodilators in patients, but they are routinely used in combination with each other.

  • Gout medications. Gout is a painful inflammation of the joint. Gout medications may increase the effects of some antibiotics.

  • Alcohol. Some antibiotics may increase the risk of liver damage from alcohol abuse.

  • Caffeine. Some antibiotics may increase the risk of toxicity (or overdose) from caffeine.