Technetium Tc-99m pentetate (Draximage DTPA) is a radiopharmaceutical imaging agent that is used in the assessment of various diseases including GFR estimation and brain imaging.

Tc-99m pentetate Uses:

• Imaging agent:

  • It is a radiopharmaceutical imaging product used for brain imaging. It is used for renal visualization for renal perfusion assessment and glomerular filtration rate (GFR) estimation.
  • It can also be used as lung ventilation imaging and evaluation of pulmonary embolism when used in combination with perfusion imaging

• Off Label Use of Technetium Tc-99m pentetate in Adults:

  • Cystography.
  • Evaluation of renovascular hypertension.
  • CSF leak detection.

Tc-99m pentetate Dose in Adults

It should be noted that Drax Imaging DTPA has been stopped in the US for more than 1 year. The dose should be checked with an appropriate radioactivity calibration system immediately before administration. Do not give more than 1 dose.

Tc-99m pentetate Dose in Brain imaging:

• IV: It can be given as 10 to 20 mCi (370 to 740 MBq). For immediate dynamic imaging, obtain at least 1 blood-pool image in the same position as flow. Its delayed images can be obtained 1 hour later.

Dose in the GFR estimation (with renal visualization):

• IV: It can be given as 3 to 5 mCi (111 to 185 MBq).
• Immediate dynamic imaging should be done. The static imaging should be done 1 to 30 minutes after administration.

Tc-99m pentetate Dose in the GFR estimation (no renal imaging):

• IV: Its dose is 0.2 to 0.5 mCi (7.4 to 18.5 MBq).

Dose in renal perfusion assessment (with renal visualization):

• IV: Its dose is 10 to 20 mCi (370 to 740 MBq). The dynamic imaging should be done immediately. Static imaging is done 1 to 30 minutes after administration.

Tc-99m pentetate Dose in the CSF leak detection (off-label):

• Intrathecal: It is given in Subarachnoid space as 1 to 3 mCi (37 to 11 MBq).

Dose in the retrograde cystography (off-label):

• Intracatheter (urethral): It is given as 0.5 to 1 mCi (18.5 to 37 MBq) (ACR 2010)

Dose in anterograde cystography (off-label):

• IV: 10 to 15 mCi.

Tc-99m pentetate Dose in the Evaluation of renovascular hypertension (off-label):

• IV: 1 to 10 mCi (185 to 370 MBq).

Tc-99m pentetate dose in the Lung ventilation scanning:

• Inhalation via nebulizer:
  • The dose is 25 to 50 mCi (925 to 1850 MBq).
  • This is done to achieve a lung dose of 0.5 to 1 mCi (18.5 to 37 MBq).
  • For imaging to be performed before perfusion imaging, the target dose should be achieved after 3 to 5 minutes of inhalation or at an imaging count of 50,000 to 100,000/minute.
  • For imaging to be performed after perfusion imaging, the target count rate should be approximately 3 times that of the perfusion count rate.

Tc-99m pentetate Dose in Childrens

It should be noted that Drax Image DTPA has been stopped in the US for more than 1 year. The dose should be measured with an appropriate radioactivity calibration system immediately prior to administration. Do not administer more than 1 dose.

Tc-99m pentetate Dose in Brain imaging (off-label):

• IV: 0.2 mCi/kg (7.4 MBq/kg).
• The minimum dose is 10 mCi (370 MBq) and the maximum dose is 20 mCi (740 MBq).

Tc-99m pentetate Dose in anterograde cystography (off-label):

• IV: 0.1 to 0.2 mCi/kg (3.7 to 7.4 MBq/kg).
• The minimum dose is 1 mCi (37 MBq) and the maximum dose is 10 mCi (370 MBq).

Tc-99m pentetate Dose in retrograde Cystography (off-label):

• Intracatheter:
  • For urethral imaging, the dose is given as 0.5 to 1 mCi (18.5 to 37 MBq).
  • One may consider 0.25 to 0.5 mCi (9.25 to 18.5 MBq) in infants and toddlers. The dose should not be exceeded from 1 mCi (37MBq) per bladder-filling cycle.

Tc-99m pentetate Dose in the Diuretic renography (off-label):

• IV: 0.1 mCi/kg (3.7 MBq/kg).
• The minimum dose is 1 mCi (37 MBq).

Tc-99m pentetate Dose in the Evaluation of renovascular hypertension (off-label):

• IV: 0.1 mCi/kg (3.7 MBq/kg).

Tc-99m pentetate Dose in the GFR estimation (no renal imaging):

• IV: 0.2 to 0.5 mCi (7.4 to 18.5 MBq).

Tc-99m pentetate Dose in Lung ventilation scanning:

• Inhalation via nebulizer:  25 mCi (925 MBq) is the dose that is given to achieve a lung dose of ~0.5 mCi (18.5 MBq).
• For imaging to be performed prior to perfusion imaging, the target dose should be achieved at an imaging count of ~10,000 to 50,000/minute.
• For imaging to be performed after perfusion imaging, the target count rate should be 3 times that of the perfusion count rate.

Tc-99m pentetate Dose in the assessment of renal perfusion (with renal visualization):

• IV: 0.1 to 0.2 mCi/kg (3.7 to 7.4 MBq/kg).
• The minimum dose is 1 mCi (37 MBq) and the maximum dose is 5 mCi (185 MBq).
• The dynamic imaging should be done immediately. And static imaging should be performed 1 to 30 minutes after administration.

Tc-99m pentetate Pregnancy Risk Category: C

• Animal reproduction has not been studied to determine the effects of this drug.
• Technetium Tc99m can be found in fetal tissue. The amount of Technetium Tc 99m depends on the formulation used, the route taken and the trimester.
• According to some studies, technetium Tc99m pentetate can be used in diagnosing certain pregnant patients.
• Increased fluid intake and frequent voiding can help reduce the risk of fetal exposure.
• It is safe for us to conclude that radiopharmaceuticals can cause harm to fetuses depending on how much they are absorbed and which trimester.
• High doses of radiopharmaceuticals, if used for therapeutic procedures has more probability to result in fetal harm.
• Modifying a medically necessary diagnostic procedure to reduce fetal risk is possible.
• It is possible to delay elective diagnostic procedures until after delivery.
• Women with potential childbearing ability should rule out pregnancy before undergoing such a procedure.
• The manufacturer suggests that women with reproductive potential should have elective procedures within the first 10 days of menstruation.
• Pregnant women should have a pulmonary scintigraphy done to diagnose pulmonary embolism.

Technetium Tc-99m pentetate use during breastfeeding:

• It is unknown if technetium Tc99m is secreted into breast milk.
• However, it is clear that breastfeeding should be stopped during therapy.
• This decision must take into consideration the health and well-being of the infant as well as the diagnostic needs of mother.
• Many clinicians recommend that breast-feeding should be stopped for longer than four hours. 
• Other research has shown that breast-feeding should be stopped after 12 hours, or longer, due to the variable excretion rate of technetium 99 pentetate in breast milk.
• In general, following the administration of radiopharmaceuticals, women with a well-established milk supply should pump at normal feeding times and discard the milk until breastfeeding can be reinitiated.
• Technetium Tc99m excretion into colostrum can be highly variable, and information is scarce.
•  It is therefore impossible to make preferences regarding early breast-feeding.
• It is important to delay elective diagnostic procedures until after breastfeeding has stopped.
• It all depends on the dosage and compliance with regulations regarding patient instructions and recordkeeping.

Dose in Kidney Disease:

There are no specific dose adjustments in renal diseases.

Dose in Liver disease:

There are no dose adjustments in liver diseases.

Side effects of Tc-99m pentetate:

• headache
• nausea
• vomiting
• flusching
• wheezing
• chest pain
• dizziness

Contraindication to Technetium Tc-99m pentetate:

Hypersensitivity to technetium 99m pentetate, or any component of the formula, is a serious contraindication.

Warnings and precautions

• Bronchospasm

  • Acute bronchospasm can occur, especially for patients with asthma or other allergic conditions. Bronchitis should be evaluated in all patients.

• Hypersensitivity

  • Reports of hypersensitivity reactions such as anaphylaxis were made. 
  • During its administration, the appropriate equipment and personnel should be available to manage such incidents.
  • Pay attention to hypersensitivity reactions.

• Radiation accumulation:

  • The patient's cumulative long-term radiation exposure is increased by the administration of Tc99m.
  • A higher risk of malignancy is associated with long-term cumulative radiation exposure.
  • Imaging should only be performed at the lowest dose. Radiation exposure should be minimized for patients and their health care providers.
  • Pediatric patients are at greater risk due to their longer life expectancy and greater radiosensitivity.

Monitoring parameters:

Observe for signs & symptoms of acute bronchospasm and hypersensitivity.

How to administer Technetium Tc-99m pentetate?

Inhalation:

• A disposable nebulizer is required for this purpose. Rinse mouth and expectorate after use to minimize mouth and esophagus radiation exposure.

IV:

• It should be not for direct IV injection. The only reconstituted technetium Tc 99m pentetate can be administered intravenously.
• Ensure sufficient hydration before and after administration. Urine should be voided frequently for 4 to 6 hours post-administration to minimize bladder radiation exposure.

While handling radiopharmaceutical products the use of appropriate precautions for handling and disposal should be ensured. Use waterproof gloves and effective radiation shielding when handling.

Mechanism of action of Technetium Tc-99m pentetate:

It is a radioactive diagnostic material that decays through an isomeric transition and emits a photon which can be detected using imaging.

Distribution:

• IV: It is distributed throughout extracellular fluid space

Bioavailability:

• Inhalation: ~70%

Protein binding:

• IV: ~4% to 10%

Half-life elimination:

• IV: 2.1 hours. Its Decay half-life is 6 hours

Time to peak:

• Inhalation: less than 2 hours

Excretion:

• IV: Urine (~100%)

International Brand Names of Technetium Tc-99m pentetate:

• DTPA
• Pentastan
• Technescan
• Drax Image DTPA

Tc-99m pentetate Brand Names in Pakistan:

No Brands Available in Pakistan.