Radiopharmacokinetics of radioiodine in the parotid glands after the administration of lemon juice.

BACKGROUND

The ability of sialagogues to increase or decrease radiation induced-sialoadenitis and/or xerostomia after therapeutic administration of ¹³¹I is controversial. To evaluate this we measured the radiopharmacokinetics of ¹²³I in the parotid glands (PGs) after its administration of lemon juice (LJ).

METHODS

A retrospective review was performed on all patients who had a salivary gland scan performed before ¹³¹I therapy between July 2008 and April 2009 at the Washington Hospital Center. Two hours after ¹²³I was given orally, dynamic scintigraphy was initiated. Five milliliters of LJ was given 5 minutes later. Then, the patient was imaged for 1 hour (phase 1) at which point the sequence was repeated (phase 2). Twenty-three patients were studied. For each PG, the presence or absence of uptake was assessed, and based on background corrected counts, the mean, range, and standard deviation were determined for multiple radiopharmacokinetic parameters such as (i) percent radioiodine washout, (ii) time from LJ administration to re-accumulation of radioiodine to pre-LJ activity, and (iii) percent reduction in radiation absorbed dose to the PGs if LJ had been re-administered at the time the radioiodine activity re-accumulated to the pre-LJ activity.

RESULTS

The mean  ± one standard deviation and range for percent washout were 84%  ± 18% (35%-100%) and 83%  ±  21% (37%-100%) in phase 1 and 2, respectively. The times from LJ to re-accumulation of the radioiodine to the pre-LJ activity were 21  ± 10 minutes (4-45 minutes) and 40  ± 14 minutes (12-62 minutes) for phase 1 and 2, respectively. The estimated percent reduction in radiation absorbed dose to the PGs following the first and second administration of LJ was 37%  ± 14% (13%-93%) and 47% ± 16% (21%-97%), respectively.

CONCLUSIONS

The washout of radioiodine from the PGs is rapid but transient. Early repeat administration may result in continued and cumulative reduction of radiation absorbed dose in the PGs.