Tobramycin: Uses, adverse effects & interactions!

Tobramycin is a broad spectrum antibiotic of the aminoglycoside class. It is particularly effective against gram negative bacteria.

USES FOR TOBRAMYCIN

  • In combination with dexamethasone, particularly used for treatment of bacterial infections of the eye.
  • Chronic bacterial infection in patients with cystic fibrosis.
  • Tobramycin also given as an injection in life threatening infections like;
  • Sepsis
  • Meningitis
  • Lower respiratory tract infections
  • Intra abdominal infections
  • Skin infections
  • Bone infections
  • UTI.

DOSAGE

Dosage forms available:

  • Respiratory inhalation solution: 300 mg/5 ml
  • Injection (IV or IM) route: 10 mg/ml, 40 mg/ml, 60 mg/ml, 80 mg/ml
  • Tobramycin ophthalmic solution/drops: 0.3%
  • Dexamethasone + Tobramycin¬† ophthalmic solution/drops: 3 mg + 1 mg/ 1 ml
  • Tobramycin + dexamethasone ophthalmic ointment: 3 mg + 1 mg/ 1 g.

Dosage guidelines:

  • In bacterial eye infection, the ointment should be applied twice a day & eye drops should be administered, three times in a day.
  • Injection given via IV or IM route in severe complication of infections, like cystic fibrosis.
  • Other doses depend on factors like the type & location of infection, bacteria, age, sex, presence of underlying diseases, immunity & doctor’s guidance.

Missed dose: Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

Overdose: In case of overdose, remove the applied ointment or wash the eyes.

SIDE EFFECTS OF TOBRAMYCIN

  • Irritation to the eye
  • Itching
  • Swelling
  • Watering of the eye
  • Headache
  • Fever
  • Rash
  • Weakness.

ADVERSE EFFECTS

  • Temporary or permanent hearing loss
  • Neurotoxicity
  • Low blood pressure
  • Drowsiness
  • Anaphylactic shock
  • Systemic toxicity
  • Anemia
  • Increased WBC count
  • Kidney damage
  • Vertigo.

PRECAUTIONS & CONTRAINDICATIONS

Tobramycin is contraindicated and precaution is advised in patients with following conditions:

  • Kidney damage can occur in patients with existing kidney disease or dysfunction.
  • In patients that are given anesthesia, neuromuscular blockade can occur if tobramycin is given subsequently.
  • In patients with hypocalcemia
  • Myasthenia gravis
  • Parkinson’s disease
  • Patients with renal disease
  • Impaired immune function
  • Allergy to aminoglycoside drugs
  • Patients with chronic diarrhea or on diuretic medication
  • In patients with auditory impairment.

INTERACTIONS OF TOBRAMYCIN

  • In presence of neuromuscular blockers, can lead to nephrotoxicity.
  • When given in presence of CCBs can lead to neuromuscular blockade.
  • Tobramycin given in presence/conjunction of diuretics can lead to increased serum concentration and reduced excretion of tobramycin, which causes toxicity.
  • When combined with warfarin can lead to increased bleeding.
  • The drug can increase the serum level of some antivirals like acyclovir & abacavir.
  • Drugs that can harm kidneys like aspirin should not be given along with tobramycin for longer duration.
  • When given in combination with cefixime gives an additive bactericidal effect.

IN PREGNANCY, BREAST FEEDING & CHILDREN

  • Pregnancy: It is a pregnancy category B drug, not enough evidence & information is available regarding this profile.
  • Breast Feeding: It enters the breast milk & is generally contraindicated.
  • Children: Aminoglycosides are not recommended in children and infants due to decreased renal immunity & development, therefore potential for toxicity.