Therapeutic drug monitoring can avoid iatrogenic alterations caused by 99mTc-methylene diphosphonate (MDP)-gentamicin interaction.

Gentamicin is an aminoglycoside antibiotic used to treat a wide variety of infections caused by gram-negative organisms, but it is potentially toxic to the kidneys. Due to its nephrotoxicity, gentamicin may cause abnormal renal uptake to be seen on 99mTc-MDP bone scintigraphy. The presence of the radiopharmaceutical in the kidneys, along with an increase in renal retention, tend to produce scintigraphic results that falsely identify characteristics related to diseases such as renal vascular, or urinary tract obstruction, and even renal cancer. An altered biodistribution may provide misleading information that can either mask or mimic certain disease symptoms. A method to maximize the therapeutic benefit of gentamicin while minimizing the risk of nephrotoxicity and the appearance of a hot kidney on scintigraphy is desirable. Serial pharmacokinetic dosing has been proposed as a method to accomplish this goal. Therapeutic drug monitoring (TDM) of gentamicin therapy, and bone scintigraphy employing 99mTc-MDP as the radiopharmaceutical was carried out in 22 patients. The data presented here demonstrate that with serial pharmacokinetic dosing of gentamicin, the iatrogenic alteration caused by gentamicin therapy can be avoided.