Renocis: Uses, Dosage & Side Effects

What Is Renocis and What Is It Used For?

Renocis is a sterile “cold kit” marketed for the preparation of technetium-99m succimer (^99mTc-DMSA) injection, one of the most widely used radiopharmaceuticals in clinical nephro-urology. The kit itself does not contain any radioactivity when supplied: it is a lyophilized (freeze-dried) powder containing succimer (dimercaptosuccinic acid, DMSA) together with stannous chloride as a reducing agent, plus stabilizers and buffers. Immediately before use, hospital radiopharmacists reconstitute the kit with a sterile solution of sodium pertechnetate (^99mTc) obtained from a technetium generator. This produces the biologically active complex ^99mTc-DMSA, which is then administered as a single intravenous injection.

Technetium-99m is the most important radionuclide in diagnostic nuclear medicine because it emits a pure gamma photon of 140 keV – ideal for gamma camera imaging – while its short physical half-life of approximately 6 hours limits radiation exposure. When combined with the DMSA chelator, a radiopharmaceutical is obtained that is specifically retained by the proximal tubular cells of the renal cortex. About 40–50% of the injected activity localizes in the functional renal parenchyma within 1–3 hours, producing images that directly reflect the distribution of viable nephrons.

The clinical value of a ^99mTc-DMSA (Renocis) scan lies in its ability to visualize functioning renal cortical tissue rather than urinary drainage. Unlike renal scintigraphy agents such as MAG3 or DTPA, which are excreted rapidly through the urinary tract and are used to study perfusion and drainage, DMSA is retained in the tubular cells for hours. This prolonged cortical retention enables high-contrast static images of the kidneys, highlighting areas of reduced or absent uptake that correspond to scarring, acute inflammation, infarction, dysplasia or other cortical abnormalities.

Renocis is approved and widely used in Europe and many other regions for the following indications:

• Evaluation of differential (split) renal function: Quantifying the percentage contribution of each kidney to total function, a measurement that is essential when planning urological surgery (for example in patients with obstructive uropathy, renal tumors, or before donor nephrectomy).
• Detection of renal cortical scarring: Identifying permanent parenchymal damage after repeated urinary tract infections, particularly in the context of vesicoureteral reflux (VUR). Renal scars appear as focal or generalized defects on the cortical surface.
• Diagnosis of acute pyelonephritis: In equivocal clinical cases, early Renocis imaging (within the first week after the acute episode) can demonstrate focal parenchymal inflammation, which appears as areas of reduced DMSA uptake without cortical volume loss.
• Assessment of congenital renal anomalies: Locating ectopic kidneys, confirming the diagnosis of horseshoe kidney, evaluating duplex collecting systems, and documenting the function of dysplastic or hypoplastic renal units.
• Follow-up after renal trauma or infarction: Characterizing the extent of functional parenchymal loss after blunt abdominal trauma or vascular events.
• Evaluation of renal transplants and complex urological reconstructions: Although other radiotracers are generally preferred for transplant assessment, DMSA may be used to define residual cortical mass in selected cases.

DMSA imaging is considered the gold standard for detecting and monitoring renal cortical scars in children, particularly those with a history of recurrent urinary tract infection. Current European and international guidelines (EAU/ESPU pediatric urology guidelines, EANM pediatric procedure guidelines, NICE and AAP recommendations) recognize DMSA scintigraphy as the reference method against which all other imaging modalities are compared.

What Should You Know Before Receiving Renocis?

Administration of a radiopharmaceutical is a regulated medical procedure governed by strict rules of justification, optimization and dose limitation as defined by the International Commission on Radiological Protection (ICRP) and the European Directive 2013/59/Euratom. Before you receive Renocis, the referring clinician and the nuclear medicine physician must be satisfied that the information expected from the scan will change clinical management and that no suitable non-ionizing alternative (such as ultrasound or MRI) is available.

Contraindications

There are relatively few absolute contraindications to Renocis, but they must be respected.

• Known hypersensitivity: Renocis should not be administered to patients with a documented allergy to succimer (DMSA), technetium-99m compounds, or any of the excipients listed in section 7 of this article.
• Confirmed pregnancy: Administration of radioactive substances to a pregnant woman is contraindicated except in rare life-threatening situations where the benefit clearly outweighs the risk to the fetus.
• Severe hypersensitivity reaction to a previous radiopharmaceutical: Patients who have experienced severe reactions to technetium-99m agents in the past require careful reassessment before re-exposure.

Warnings and Precautions

Tell your doctor or the nuclear medicine team before the procedure if any of the following apply to you:

• Pregnancy or possible pregnancy: If you are pregnant, think you might be pregnant, or if your period is overdue, you must inform staff before any injection. A pregnancy test may be requested for women of childbearing potential.
• Breastfeeding: Breast milk can transfer a small fraction of the administered activity. Temporary interruption of breastfeeding is required after the injection (see section on breastfeeding below).
• Impaired renal function: Renal failure reduces the contrast between functional and non-functional tissue. Images may be more difficult to interpret, though the scan can still provide useful qualitative information.
• Recent administration of other radiopharmaceuticals: Residual activity from previous scans (for example a bone scan using another ^99mTc agent) may interfere with interpretation. Tell the nuclear medicine team about any recent nuclear medicine procedure.
• Use of medicines affecting renal handling: ACE inhibitors, angiotensin receptor blockers, NSAIDs, iron supplements, ammonium chloride and sodium bicarbonate may modify renal uptake of DMSA.
• Severe dehydration: Patients should be well hydrated before and after the scan to improve image quality and accelerate urinary elimination of any non-retained tracer.
• Anxiety, claustrophobia, or inability to lie still: Imaging requires the patient to remain motionless on the gamma camera table for 20–45 minutes. Young children, anxious patients or those in severe pain may require special preparation or sedation in selected cases.
• Recent intake of iodinated contrast media: Although not a formal contraindication, recent contrast studies may alter renal handling of DMSA in patients with pre-existing renal disease.

The nuclear medicine team will ensure you are well hydrated, ask you to void before imaging (to reduce background activity from the bladder), and confirm that you can tolerate the acquisition time. The injection itself is well tolerated and the test is painless apart from the initial venipuncture.

Use in Children and Adolescents

Renocis is widely used in children and adolescents, where it remains the preferred modality for assessing renal scarring and split function. The activity administered is calculated according to body weight using the EANM Pediatric Dosage Card, which provides evidence-based minimum activities designed to yield adequate image quality while minimizing radiation exposure. Pediatric preparation often involves reassurance, distraction techniques, use of topical anesthetic cream at the venipuncture site, and – in very young or uncooperative children – mild sedation if clinically warranted.

Pregnancy and Breastfeeding

Administration of radiopharmaceuticals to pregnant women is generally avoided unless the scan is essential and no suitable alternative exists. The fetal dose from a ^99mTc-DMSA scan is relatively low (approximately 0.5–1.0 mGy at standard adult activities, depending on gestational age), but any prenatal radiation exposure carries a small theoretical risk. Before any administration, pregnancy must be excluded by clinical history and, when appropriate, a pregnancy test in women of childbearing potential. If Renocis is unavoidable during pregnancy, the lowest diagnostic activity must be used and the patient must be counseled about the residual risks.

If you are breastfeeding, the nuclear medicine team will give specific instructions. International guidance recommends interrupting breastfeeding for approximately 12 hours (some national authorities recommend up to 24 hours) after administration of ^99mTc-DMSA. During this period, milk should be expressed and discarded to maintain lactation. Close physical contact with the infant (prolonged cuddling, skin-to-skin contact) should also be limited during the first 12–24 hours to reduce external dose to the child.

Driving and Operating Machinery

Renocis does not have known pharmacological effects on the central nervous system and does not impair alertness, coordination or reaction time. You may drive or operate machinery after the scan. However, very young children, anxious patients, or those who have received sedation may require a period of observation and should not drive themselves home.

Radiation Protection Advice After Your Scan

After the injection, a small amount of radioactivity circulates in your body and is gradually eliminated through the urine and through radioactive decay. To minimize exposure to yourself and others:

• Drink plenty of fluids for the first 24 hours to accelerate urinary elimination.
• Empty your bladder frequently, sitting down on the toilet and flushing twice.
• Wash your hands thoroughly after each visit to the toilet.
• Avoid close, prolonged contact with pregnant women, infants and young children for the first 12–24 hours (this is particularly important in adult patients who receive higher activities).
• Inform border officials, airports or customs if you need to travel within 2–3 days of the scan, as sensitive radiation detectors may alarm; your nuclear medicine department can provide a certificate.

How Does Renocis Interact with Other Drugs?

Because Renocis is administered in microgram amounts of succimer together with a trace of technetium-99m, classic pharmacological drug–drug interactions are not the main concern. Instead, interactions are mostly physiological: they involve substances that alter renal perfusion, tubular cell metabolism, urinary pH, or competitive uptake of DMSA by the proximal tubule. These interactions can produce misleading images by reducing, redistributing or accelerating clearance of the tracer.

Major Interactions

Minor Interactions and Technical Considerations

Before the appointment you should provide a complete medication list, including prescription drugs, over-the-counter products, herbal supplements and recent radiopharmaceuticals. The nuclear medicine physician will decide whether any medicine should be temporarily paused, and your referring doctor will assist if treatment adjustments are needed. Do not stop any medication on your own initiative.

What Is the Correct Dosage of Renocis?

Renocis is always administered by a physician or authorized radiographer in a licensed nuclear medicine facility. The injected activity (the radioactive dose, measured in megabecquerels, MBq) is not the same as the mass dose of succimer: it reflects the number of radioactive decays per second and is what determines both image quality and radiation exposure. The prescribing nuclear medicine physician selects the optimal activity based on patient body weight, the specific clinical question and the imaging equipment available.

Adults

Children

Elderly

Renal Impairment

Missed or Repeated Scans

Because Renocis is given as a single diagnostic dose during a scheduled appointment, there is no concept of a “missed dose” in the traditional therapeutic sense. If the injection fails due to extravasation or if image quality is insufficient, the scan can be repeated. However, repeat administration should be postponed for several weeks whenever feasible to avoid unnecessary radiation exposure. Follow-up DMSA scans for children with recurrent urinary tract infection are typically performed at 6–12 month intervals, allowing time for any acute inflammatory changes to resolve before assessing permanent scarring.

Radiation Overdose

Accidental administration of an excessive activity is very rare because all radiopharmaceuticals are prepared and verified by a qualified radiopharmacist. If it occurred, the absorbed dose to the patient could be reduced by encouraging frequent voiding and generous fluid intake to accelerate urinary elimination. Cholestyramine or other non-specific measures have limited effect because DMSA is handled almost entirely by the kidneys. The physical half-life of technetium-99m (6 hours) ensures rapid spontaneous decay of the radioactivity.

How Renocis Is Given

On the day of the examination, a radiopharmacist reconstitutes the Renocis vial with a sterile solution of sodium pertechnetate (^99mTc) obtained from a technetium generator. The mixture is gently swirled and allowed to stand for about 15 minutes, during which the DMSA is labeled with technetium-99m. Quality control (including radiochemical purity testing by thin-layer chromatography) is then performed to verify that the labeling yield exceeds 95%. Only a preparation meeting the release criteria may be administered.

The prepared ^99mTc-DMSA is drawn up into a shielded syringe, verified against the patient’s identity and prescribed activity, and injected slowly into a peripheral vein (usually the antecubital fossa). The injection itself takes only a few seconds, followed by a saline flush to ensure complete delivery. You will then be asked to drink fluids and return to the department at the scheduled imaging time (usually between 2 and 6 hours later). At imaging, you will lie supine on the gamma camera table while planar (anterior and posterior) or SPECT images are acquired; the acquisition itself typically takes 20–45 minutes.

What Are the Side Effects of Renocis?

Renocis is remarkably well tolerated. At a standard adult activity of 100 MBq, only a few hundred micrograms of succimer are administered, which is several orders of magnitude below doses that could produce pharmacological effects. The most important risks to consider are therefore rare hypersensitivity reactions and the small absorbed radiation dose. Serious adverse reactions are extremely rare, but every nuclear medicine department is equipped to manage them promptly.

Radiation Exposure

At a standard adult activity of 100 MBq, the effective radiation dose from a Renocis scan is approximately 0.7–1.0 mSv. This is less than the average natural background radiation most people receive over one year (about 2–3 mSv worldwide) and less than a single abdominal CT scan (typically 5–10 mSv). The main radiation-sensitive organs during a DMSA scan are the kidneys themselves (absorbed dose of the order of several mGy at the cortex), followed by the bladder wall. There is no acute radiation effect at these levels; the only theoretical concern is a very small long-term increase in stochastic cancer risk, which is why the lowest diagnostic activity is always used.

Frequency of Adverse Reactions

The side effects below are classified according to the standard frequency categories used in European Summaries of Product Characteristics. For Tc-99m DMSA products, most adverse reactions belong to the “rare” or “very rare” categories.

Reporting Suspected Side Effects

If you experience any unexpected symptoms during or after a Renocis scan, tell the nuclear medicine staff immediately, and inform your referring physician at your next appointment. Healthcare professionals and patients can also report suspected adverse reactions through their national pharmacovigilance system (for example the MHRA Yellow Card Scheme in the United Kingdom, the EMA EudraVigilance system in the European Union, or the FDA MedWatch program in the United States). Reporting suspected adverse reactions after authorization of the medicinal product is important, as it allows continued monitoring of the benefit/risk balance of Renocis.

How Should Renocis Be Stored?

Because Renocis is supplied to hospital radiopharmacies and is never dispensed to patients, storage will not normally concern you personally. However, understanding the basic rules can help clarify how the product is handled and why every step must be traceable.

• Non-radioactive kit (unopened): Store the vial in the outer carton at a controlled room temperature – refer to the product’s approved labeling for the exact specification (typically 2–25°C). Protect from light and keep the vial in its original packaging to ensure chemical stability.
• Freezing: Do not freeze the kit unless specifically authorized by the manufacturer.
• Expiry date: Do not use after the expiry date printed on the carton. The expiry date refers to the last day of that month.
• Reconstituted radiopharmaceutical: Once labeled with ^99mTc, the product must be used within the in-use shelf life specified in the approved instructions (commonly up to 6 hours at 2–25°C). The radioactivity naturally decays with a half-life of approximately 6 hours, meaning the usable activity falls by 50% every 6 hours.
• Quality control: Each prepared batch is tested for radiochemical purity before administration. A preparation that does not meet the release criteria must not be used.
• Waste disposal: Radioactive waste (used vials, syringes, swabs, gloves, paper towels) is segregated and stored in shielded containers until its radioactivity has decayed to background levels. It is then disposed of according to national radiation protection regulations.
• Environmental considerations: Do not dispose of any radiopharmaceutical via domestic wastewater or household refuse. All handling takes place exclusively within the hospital radiopharmacy and nuclear medicine department.

Because technetium-99m has such a short physical half-life, Renocis vials are typically ordered for use on the same day and are not held in large hospital stockpiles. Coordinated scheduling between the radiopharmacy, the nuclear medicine department and the patient is essential to ensure that the prepared activity is available exactly when needed.

What Does Renocis Contain?

Active Substance

The active substance is succimer (also known as meso-2,3-dimercaptosuccinic acid, DMSA). Each multidose vial typically contains 1.2 mg of succimer as a lyophilized powder. This small mass of chelator is what forms the ^99mTc-DMSA complex when the kit is reconstituted with sodium pertechnetate (^99mTc) solution. Several patient doses can be prepared from a single vial, depending on the volume and activity added.

Inactive Ingredients (Excipients)

The excipients included in the Renocis kit are carefully selected to stabilize succimer in the reduced form needed for radiolabeling and to maintain an appropriate pH. Typical excipients include:

• Stannous chloride dihydrate – provides the reducing environment required to transform pertechnetate (^99mTc VII+) into the lower oxidation state that binds to DMSA.
• Inositol – stabilizer and lyophilization support.
• Ascorbic acid (vitamin C) – antioxidant that prevents re-oxidation of the stannous/tin complex.
• Nitrogen – used to fill the headspace of the vial to limit oxidation.
• Buffer components (such as sodium hydroxide or hydrochloric acid) – adjust the pH of the reconstituted preparation to a physiological range, typically 2.5–3.5 in the intermediate vial before buffering, reaching approximately 4–5 after mixing with the pertechnetate solution.

The exact excipient composition depends on the specific formulation and should be confirmed against the approved Summary of Product Characteristics (SmPC) of the product supplied in your country. No excipients of animal origin are used. The kit does not contain lactose, gluten or preservatives such as benzyl alcohol.

The Radioactive Component

The kit itself does not contain any radioactivity. Technetium-99m (^99mTc) is added at the point of use in the form of sterile sodium pertechnetate (^99mTc) injection obtained from a hospital ⁹⁹Mo/^99mTc generator. Technetium-99m decays by isomeric transition with a physical half-life of 6.02 hours, emitting a 140 keV gamma photon that is ideally suited to modern gamma camera imaging. After decay it produces ⁹⁹Tc, a long-lived but very low-activity nuclide that decays further to stable ruthenium-99.

Appearance

Renocis is supplied as a white to off-white sterile lyophilized powder in a multidose glass vial with a rubber stopper and an aluminum/plastic overseal. After reconstitution with sodium pertechnetate (^99mTc) solution, the resulting liquid is clear and colorless. A slight cloudiness, discoloration, or visible particulate matter means that the preparation must not be used.

Manufacturer and Marketing Authorization Holder

Renocis is manufactured and marketed by Curium, one of the world’s leading producers of diagnostic and therapeutic radiopharmaceuticals. The product was historically developed and marketed by CIS bio international in France, which has since become part of the Curium group. National marketing authorizations are held by Curium subsidiaries in the respective countries of distribution.

Packaging

Renocis is typically supplied in cartons containing multiple multidose vials designed for radiopharmacy preparation. Packaging may vary between countries and institutions depending on local supply agreements and is not intended for individual patient distribution.