Tobramycin Trough Level, Serum or Plasma, by Mass Concentration

What Is Tobramycin?

Tobramycin is an aminoglycoside antibiotic used to treat certain serious bacterial infections, including some lung, blood, and urinary infections. It is often given by injection or infusion in a hospital or clinic setting, and sometimes by inhalation for people with cystic fibrosis. Because the safe range between an effective dose and a harmful dose is fairly narrow, monitoring blood levels is important.

Why Measure a Trough Level?

A trough level is drawn shortly before the next scheduled dose, when the drug is at its lowest point in your blood. Checking this low point helps your care team see whether the drug is being cleared from your body properly. If the trough is too high, the drug may accumulate and raise the risk of side effects; if levels are not where they should be, the dose or timing may be adjusted.

How the Test Is Done

A member of your care team collects a small blood sample from a vein, usually in your arm. Timing matters a great deal: the sample must be taken at the correct time relative to your dose, so tell staff about any recent doses. Results are typically reported as a concentration in the blood, and your care team interprets them together with your dosing schedule and kidney function.

What Affects Your Results

Your result can be influenced by how well your kidneys are working, your age and body weight, hydration, other medicines you take, and exactly when the sample was drawn. Because of this, the number is always interpreted in context rather than on its own. Your care team may repeat the test and adjust the dose based on the pattern of results over time.