TechneScan HDP (Technetium-99m Oxidronate Kit)

What Is TechneScan HDP and What Is It Used For?

TechneScan HDP belongs to a group of medicines known as diagnostic radiopharmaceuticals. Unlike conventional medicines, which are intended to treat disease, a diagnostic radiopharmaceutical is administered in trace amounts so that clinicians can use external gamma-camera imaging to visualize the function and pathology of specific organs or tissues. TechneScan HDP itself is not radioactive; it is a sterile “cold kit” containing a diphosphonate ligand (oxidronate, often abbreviated HDP for hydroxymethylene diphosphonate) together with a stannous chloride reducing agent and excipients. The kit is converted to the active radiopharmaceutical, technetium-99m oxidronate (99mTc-HDP), by reconstituting it in a radiopharmacy with sterile sodium pertechnetate (99mTc) eluted from a 99Mo/99mTc generator.

Technetium-99m diphosphonate agents — including HDP, methylene diphosphonate (MDP) and hydroxyethylene diphosphonate (HEDP) — are the global standard for bone scintigraphy. Several million bone scans are performed worldwide every year using these compounds, and they remain indispensable in oncology, orthopedics, rheumatology, sports medicine, pediatrics and endocrinology. HDP-based tracers, including TechneScan HDP, are particularly valued for their rapid blood clearance, high bone-to-soft-tissue ratio and crisp images on SPECT/CT.

The finished radiopharmaceutical is classified in the WHO Anatomical Therapeutic Chemical (ATC) system under code V09BA02 — technetium (99mTc) oxidronic acid. Regulatory authorities including the European Medicines Agency (EMA), the U.K. Medicines and Healthcare products Regulatory Agency (MHRA), the U.S. Food and Drug Administration (FDA) and national licensing bodies have authorized it for the indications described below. TechneScan HDP is supplied exclusively to authorized nuclear medicine facilities and is never dispensed directly to patients.

How Does Technetium-99m Oxidronate Work?

Hydroxymethylene diphosphonate (HDP) is a synthetic analog of inorganic pyrophosphate in which the central oxygen atom has been replaced by a carbon atom, giving the molecule a stable P–C–P backbone that resists enzymatic hydrolysis. Diphosphonates bind strongly to calcium ions on the surface of the hydroxyapatite crystals that form the mineral matrix of bone. Approximately 50% of the injected activity is adsorbed to the skeleton within 2 to 6 hours, with the highest uptake in regions of active bone remodeling where osteoblasts are depositing new mineralized matrix. Uptake is further enhanced by regional hyperemia, which increases tracer delivery.

The 99mTc radiolabel decays by isomeric transition, emitting a single 140 keV gamma photon that is nearly ideal for detection with a gamma camera. Planar whole-body acquisitions, three-phase scans (vascular, blood-pool and delayed phases) and SPECT or SPECT/CT reconstructions can all be performed with the same injected dose. The remaining non-skeletal activity is cleared almost entirely through the kidneys into the urinary bladder, which is why pre-scan hydration and frequent voiding are essential for both image quality and patient dosimetry.

Because 99mTc-HDP reflects bone turnover rather than mineral content, a positive scan identifies regions of metabolically active disease well before structural changes become visible on plain radiography. Bone metastases, for example, can be detected on scintigraphy weeks to months earlier than on conventional X-ray, and the whole skeleton is surveyed in a single study. Conversely, purely lytic lesions with minimal osteoblastic response (such as some myeloma deposits) can appear falsely negative, which is why a normal bone scan does not always exclude skeletal pathology and why SPECT/CT or correlation with cross-sectional imaging is increasingly the standard of care.

Approved Diagnostic Indications

Technetium-99m oxidronate prepared from a TechneScan HDP kit is approved by regulatory authorities worldwide for a wide range of skeletal indications. These include both oncological and non-oncological uses:

• Staging and follow-up of bone metastases in cancers that commonly metastasize to bone, including breast, prostate, lung, renal cell, thyroid and gastrointestinal carcinomas.
• Evaluation of primary bone tumors such as osteosarcoma, Ewing sarcoma and chondrosarcoma (local extent, detection of skip lesions and distant metastases).
• Detection of occult, stress or insufficiency fractures, particularly where plain radiographs are inconclusive (for example scaphoid, sacral, femoral neck and tibial stress fractures).
• Osteomyelitis and septic arthritis — often as part of a three-phase study; combined 99mTc-HDP with white-cell or 67Ga scintigraphy can clarify infection versus aseptic processes.
• Complex regional pain syndrome (CRPS), where three-phase bone scintigraphy has a well-established role in diagnosis.
• Paget’s disease of bone — mapping extent of active disease and monitoring treatment response.
• Evaluation of prosthetic joint loosening and periprosthetic pain (hip, knee, shoulder) — with interpretation adapted to the age of the prosthesis.
• Assessment of metabolic bone disease, including renal osteodystrophy, hyperparathyroidism-related bone changes, osteomalacia and hypertrophic pulmonary osteoarthropathy.
• Heterotopic ossification: evaluation of maturity before surgical excision.
• Pediatric applications such as nonaccidental injury in children with suspected occult fractures, growth-plate injuries, and evaluation of unexplained limp or bone pain.
• Sports medicine: diagnosis of stress reactions, shin splints, enthesopathies and spondylolysis.

The strength of technetium-99m oxidronate lies in its capacity to survey the entire skeleton in a single examination. No other currently available imaging modality combines whole-body coverage, sensitivity to altered bone turnover, favorable radiation dosimetry and rapid throughput to the same degree. Although whole-body MRI and 18F-fluoride PET/CT are increasingly used in select centers, bone scintigraphy with 99mTc-HDP remains the most widely available and most widely validated approach worldwide.

What Should You Know Before Taking TechneScan HDP?

Every nuclear medicine examination must be preceded by a careful clinical justification that weighs the anticipated diagnostic benefit against the radiation dose. The referring physician and the nuclear medicine specialist work together to confirm that technetium-99m oxidronate is the most appropriate tracer for the clinical question, that no recent examination already answers it, and that alternative non-ionizing techniques such as MRI have been considered where feasible. This stepwise approach is codified in the ALARA principle (As Low As Reasonably Achievable) and in European and international radiation protection regulations.

Contraindications

Technetium-99m oxidronate derived from a TechneScan HDP kit must not be used in the following situations:

• Hypersensitivity: Known hypersensitivity to oxidronate, other diphosphonates, stannous (tin) ion or any excipient of the kit (for example gentisic acid, sodium chloride, sodium hydroxide or hydrochloric acid used for pH adjustment).
• Pregnancy (elective examinations): Technetium-99m oxidronate crosses the placenta and concentrates in the urinary bladder and developing fetal skeleton. Elective diagnostic procedures must be postponed until after delivery. In clinically urgent cases, the lowest possible activity must be used and the fetal dose estimated.

There is no absolute upper age limit or strict weight-based exclusion, but the suitability of the scan must always be assessed on an individual basis. Children, adolescents and adults of all ages are routinely imaged with dose adjustment.

Warnings and Precautions

Although technetium-99m oxidronate has an excellent safety profile, several important precautions apply to every examination. Patients and caregivers should be informed about these in advance so that questions can be answered before the appointment.

Ionizing radiation: Every diagnostic dose of technetium-99m oxidronate exposes the patient to a small amount of ionizing radiation. The effective dose for a typical adult whole-body bone scan is approximately 3.0–4.4 mSv, comparable to roughly 12–18 months of natural background radiation. Repeated bone scans during follow-up of oncological disease contribute cumulatively to the stochastic risk of radiation-induced cancer, which is why each procedure must be individually justified.

Hydration and bladder emptying: Patients are asked to drink approximately 500–1,000 ml of fluid in the interval between injection and imaging, and to void the bladder immediately before the delayed images are acquired. This accelerates urinary excretion of unbound tracer, markedly lowers the radiation dose to the bladder wall and surrounding pelvic organs, and improves visualization of the pelvic skeleton by reducing background activity.

Pediatric patients: Children are more radiosensitive than adults because their cells divide faster and they have a longer life expectancy during which a radiation-induced cancer might develop. For this reason, pediatric activities are always scaled down from adult activities according to the EANM Paediatric Dosage Card, which uses a body-mass-based multiplier. The minimum administrable activity recommended by the EANM must still be respected to ensure diagnostic image quality.

Renal impairment: Because technetium-99m oxidronate is cleared almost exclusively by glomerular filtration, severe renal impairment prolongs the soft-tissue background, increases the radiation dose to the bladder wall and kidneys, and may delay the optimum imaging window from 2–4 hours to 4–6 hours post-injection. Dialysis patients are typically imaged the day before their next session. The examination is not contraindicated in renal failure, but the protocol is adapted.

Extravasation: Accidental leakage of the tracer into the subcutaneous tissue during injection produces a focal “hot spot” that can obscure axillary and upper-limb skeletal interpretation and can create artefactual lymph-node uptake. Careful intravenous technique using a dedicated cannula or butterfly needle is standard practice, and any suspected extravasation should be documented.

Recent bisphosphonate therapy: High-dose intravenous bisphosphonates (for example zoledronate or pamidronate) occupy the same hydroxyapatite binding sites as HDP and can reduce overall bone uptake and sensitivity for bone metastases. Ideally, high-dose bisphosphonates should not be administered in the days immediately preceding the scan; however, this is balanced against the need for treatment and is not an absolute contraindication.

Prior radiotherapy or fractures: Previous external beam radiotherapy can suppress bone uptake in the radiation field (“cold defect”) for months to years, simulating a metastatic cold lesion. Fractures, surgical healing and orthopedic hardware produce intense focal uptake that must be carefully distinguished from disease. A detailed clinical history and previous imaging are essential for accurate interpretation.

Radiation protection for staff and close contacts: After injection, patients emit small amounts of gamma radiation until the tracer has decayed and been excreted. Staff follow strict radiation protection procedures. Patients are generally advised to avoid prolonged close contact with pregnant women and infants for the first 24 hours after the examination, to double-flush the toilet, to wash their hands thoroughly after urinating, and to follow any specific instructions given by the nuclear medicine department.

Pregnancy and Breastfeeding

Pregnancy status must be confirmed before any examination in women of childbearing potential. A urine or serum beta-hCG test is commonly performed. Detailed advice is provided below.

• Women of childbearing potential: The “10-day rule” or pregnancy test should be applied according to local protocol. If pregnancy cannot be excluded, the examination must be postponed unless clinically urgent.
• Pregnancy: Elective diagnostic use of technetium-99m oxidronate is contraindicated. If an urgent examination cannot be avoided, the lowest achievable activity should be used (typically 300–400 MBq instead of 600–740 MBq), maternal hydration should be strongly encouraged, and an indwelling urinary catheter may be used to accelerate bladder clearance and minimize fetal radiation dose. The absorbed dose to the fetus from a typical low-dose adult study is approximately 2–4 mGy, well below the established deterministic threshold for malformation.
• Breastfeeding: A small fraction of the injected 99mTc-HDP is excreted into breast milk. The European Association of Nuclear Medicine (EANM) generally recommends a short interruption of breastfeeding of at least 4 hours after injection of 99mTc-diphosphonates, with expression and discarding of milk during that period. Some national guidelines are more conservative and recommend 12–24 hours. Always follow the specific guidance of the nuclear medicine department.
• Male fertility: Diagnostic doses do not have clinically significant effects on male fertility. No specific contraceptive precautions are required.

Children and Adolescents

Technetium-99m oxidronate is frequently and safely used in infants, children and adolescents for evaluation of suspected occult fractures, osteomyelitis, bone tumors, child abuse, back pain, limb pain and unexplained limp. Pediatric activities must be scaled according to body weight using the EANM Paediatric Dosage Card. The minimum activity required to obtain diagnostic images should be used, and sedation may be required for younger children to ensure motion-free SPECT acquisitions; sedation protocols should follow institutional pediatric anesthesia policies.

Driving and Operating Machinery

Technetium-99m oxidronate does not produce any known pharmacological effect on alertness, vision or psychomotor performance at the tracer doses used. Patients are usually fit to drive home after the examination. Individual anxiety, sedation used for pediatric patients, or underlying medical conditions may affect this; always follow the specific advice of the nuclear medicine department.

How Does TechneScan HDP Interact with Other Drugs?

Because technetium-99m oxidronate is administered in such small amounts (approximately 3 mg of HDP and nanograms of technetium per dose), it does not induce or inhibit cytochrome P450 enzymes and does not compete with other drugs for plasma protein binding in any clinically meaningful way. The concept of a “drug interaction” therefore differs from that for pharmacological medicines: rather than altering blood levels or toxicity, interacting medicines primarily influence how the tracer is distributed in bone and soft tissue, which can in turn affect how the resulting scintigraphic images look.

For this reason it is essential to provide the nuclear medicine department with a complete and up-to-date list of all prescription drugs, over-the-counter products, vitamins and herbal supplements taken in the preceding weeks. In many cases specific medicines must be paused for a defined interval before the examination, and the referring clinician will usually give written instructions.

Major Interactions

The following categories of medicines have the most important effects on technetium-99m oxidronate biodistribution and frequently require dose timing adjustment or additional clinical context at interpretation.

Minor Interactions

Several additional medicines and conditions can subtly modify biodistribution. They rarely require discontinuation, but the interpreting physician should be aware of them.

What Is the Correct Dosage of TechneScan HDP?

TechneScan HDP is a kit, not a patient-administered product. The prescribed quantity is the radioactivity of the finished technetium-99m oxidronate injection, expressed in becquerels (Bq), the SI unit of radioactivity, most commonly with the prefix mega (MBq, one million disintegrations per second). Activity is measured in a calibrated dose calibrator immediately before injection because 99mTc decays by 50% every 6.02 hours and the actual activity at injection differs from the calibration time.

Administered activities must always be justified and optimized according to the ALARA principle and to national and international diagnostic reference levels (DRLs). Reference activities vary slightly between the European Association of Nuclear Medicine (EANM), the Society of Nuclear Medicine and Molecular Imaging (SNMMI) and national authorities, but they converge on similar ranges for established indications.

Adults

Children

Pediatric activities are scaled from the adult reference activity using the EANM Paediatric Dosage Card multiplier based on body weight. A minimum administrable activity of 40 MBq is defined for bone scintigraphy to ensure that images remain diagnostic — below that minimum, the signal-to-noise ratio is too poor to answer the clinical question and the child is effectively exposed to radiation for no benefit.

Elderly

No specific dose reduction is required for elderly patients on the basis of age alone. However, elderly patients often have reduced renal function, which can prolong the effective biological half-life of 99mTc-oxidronate and increase the effective dose to the bladder wall. Good hydration and encouragement of frequent voiding mitigate this effect. Delayed imaging up to 24 hours after injection may occasionally be required to clear soft-tissue background in patients with significant renal impairment.

Renal Impairment

Technetium-99m oxidronate is excreted almost exclusively by the kidneys. Severe renal impairment does not contraindicate the scan, but the nuclear medicine specialist may delay imaging, add 24-hour imaging in selected cases, and ensure aggressive hydration. Dialysis patients are typically scanned on the day before their next dialysis session to maximize background clearance. No dose adjustment of the administered activity is routinely required.

Hepatic Impairment

Because the tracer does not undergo hepatic metabolism, hepatic impairment has no significant effect on biodistribution or dosimetry, and no dose adjustment is required.

Missed Dose

Because technetium-99m oxidronate is administered as a single dose on the day of examination in a hospital setting, the concept of a “missed dose” does not apply in the usual sense. If the appointment is missed, it should be rescheduled as soon as practical. The radiopharmacy will prepare a fresh radiolabeled kit for the new appointment.

Overdose

Because the administered activity is calibrated immediately before injection, accidental overdosing is extremely rare. In the unlikely event that a substantially greater activity is administered than intended, the patient’s radiation dose can be reduced by forced diuresis (oral or intravenous fluids), frequent voiding of the bladder, and insertion of a urinary catheter if medically appropriate. There is no specific pharmacological antidote, and symptomatic management is based on the radiation dose absorbed rather than on the trace chemical mass involved. The radiation protection officer and medical physicist should be notified, the absorbed and effective doses estimated, and the event recorded and reported in line with national regulations.

What Are the Side Effects of TechneScan HDP?

Because only micrograms of HDP and nanograms of technetium are injected, technetium-99m oxidronate does not produce classical pharmacological side effects. The adverse reactions that have been reported are almost exclusively hypersensitivity and injection-site phenomena. Pharmacovigilance data from the EMA EudraVigilance database, the FDA FAERS system and the published literature consistently show adverse event rates in the range of 1–6 per 100,000 injected doses for 99mTc-diphosphonates overall, among the lowest in routinely administered injectable pharmaceuticals.

Side Effect Frequency Overview

Radiation-Related Stochastic Effects

Even at the low activities used for diagnostic examinations, ionizing radiation carries a small theoretical long-term risk of stochastic effects — primarily a slightly increased probability of radiation-induced cancer over a lifetime. The ICRP estimates the risk from a single adult 99mTc-HDP scan to be in the range of approximately 1 in 10,000 to 1 in 30,000, depending on age and sex, and this must be compared with the benefit of obtaining a diagnosis that could materially change clinical management. The risk is disproportionately higher in young children, which is why strict application of the EANM Paediatric Dosage Card is essential. Deterministic effects such as skin burns or hair loss do not occur at diagnostic doses; these are associated only with interventional fluoroscopy or therapeutic radionuclide administration, not with diagnostic bone scintigraphy.

Managing Side Effects

If a reaction occurs, it is treated symptomatically. Nuclear medicine departments are equipped with resuscitation equipment and are staffed by personnel trained to recognize and treat rare hypersensitivity reactions, following the same anaphylaxis algorithms used for iodinated contrast media. Mild infusion reactions usually resolve spontaneously within minutes and do not require specific therapy. Extravasation is prevented by careful intravenous technique; if it occurs, elevation and warm compresses generally suffice, and the site is documented to avoid misinterpretation of subsequent axillary lymph-node uptake.

Any side effect, however mild, should be reported to the nuclear medicine staff and recorded in the patient’s medical notes. National pharmacovigilance reporting systems (Yellow Card in the UK, EudraVigilance in the EU, MedWatch in the U.S.) accept reports for radiopharmaceuticals as for any other medicine.

How Should You Store TechneScan HDP?

TechneScan HDP itself is not radioactive as supplied; it is a sterile cold kit that becomes a Class 7 dangerous good (radioactive material) only after reconstitution with sodium pertechnetate (99mTc). It is therefore subject to a double layer of regulation once radiolabeled: pharmaceutical regulation (as a medicine) and radiation protection regulation (as a radioactive source). It is delivered directly from the manufacturer to the nuclear medicine department, accompanied by a Certificate of Analysis and Summary of Product Characteristics.

Storage of the Unopened Kit

• Temperature: Store at 2–25 °C according to the approved Summary of Product Characteristics. Do not freeze — freezing can damage the lyophilized powder, compromise the stannous ion’s reducing capacity, and reduce radiolabeling efficiency.
• Light: Protect from direct sunlight and strong artificial light. Keep in the original carton until use.
• Container integrity: Do not use if the rubber stopper is compromised, if the cake appearance is discolored, or if the vial shows signs of leakage.
• Access: Store in a dedicated radiopharmacy area accessible only to authorized personnel.
• Shelf life: Defined by the expiry date printed on the label (typically 12 months from the date of manufacture for unopened vials). Do not use after the expiry date.

Storage of the Reconstituted Radiopharmaceutical

• Use within 8 hours: Once reconstituted with sodium pertechnetate (99mTc), the finished technetium-99m oxidronate injection must be used within 8 hours (or as specified in the current Summary of Product Characteristics).
• Room temperature, shielded: Store the reconstituted multidose vial in its lead shielded pot at controlled room temperature (below 25 °C). Do not refrigerate and do not freeze.
• Record keeping: The time of reconstitution, calibration activity and expiration time must be recorded on the vial label in accordance with Good Radiopharmacy Practice.
• Multiple doses: The multidose vial may be used for several patients within the 8-hour window, provided that aseptic technique is maintained at every aspiration.

Disposal of Expired Kits and Spent Radiopharmaceutical

Unused unopened kits past their expiry date should be destroyed in accordance with hospital pharmaceutical waste procedures. Expired reconstituted vials and empty vials containing residual 99mTc activity are held in a dedicated decay storage area until the activity falls below regulatory clearance levels (typically 10 half-lives, or approximately 60 hours for 99mTc). They may then be disposed of as conventional clinical waste if permitted by national regulation. Radioactive waste must never be disposed of via ordinary wastewater, household waste or landfill.

Keep all medicines and radioactive sources out of the sight and reach of children. Patients and visitors should not be allowed unsupervised access to stored kits or reconstituted vials.

What Does TechneScan HDP Contain?

TechneScan HDP is supplied as a sterile, single-use, multidose kit. The active radionuclide, technetium-99m, is not present at the time the kit is manufactured; instead it is added at the point of use by reconstituting the vial with sodium pertechnetate (99mTc) eluted from a 99Mo/99mTc generator such as Poltechnet, Drytec, Gentech, Ultra-TechneKow or Elumatic. Understanding the system’s composition helps explain why the finished injection is essentially a dilute saline solution containing only microgram quantities of HDP and nanogram quantities of technetium.

Active Substance and Excipients

• Active ligand: Oxidronate sodium (chemical name: sodium hydroxymethylene diphosphonate, HDP) — typically 3.0 mg per vial in the lyophilized form.
• Reducing agent: Stannous chloride dihydrate (SnCl₂·2H₂O) — typically 0.24–0.29 mg per vial. Reduces pertechnetate (Tc(VII)) to a lower oxidation state so that it can chelate with the diphosphonate.
• Stabilizer: Gentisic acid (2,5-dihydroxybenzoic acid) — limits radiolysis of the chelate over the permissible shelf life of the reconstituted injection.
• Excipients: Sodium chloride, sodium hydroxide and/or hydrochloric acid to adjust pH.
• Radionuclide (added at reconstitution): Sodium pertechnetate (99mTc) solution eluted from a 99Mo/99mTc generator, typically 1,850–11,100 MBq per vial at the time of reconstitution, in 4–10 ml of sterile 0.9% sodium chloride.
• Final injection: Technetium-99m oxidronate injection in isotonic saline; clear, colorless, practically particle-free. No preservatives are added.

Physical and Chemical Properties

Packaging and Presentation

Each TechneScan HDP kit is typically supplied as a carton of 5 multidose glass vials, each containing the lyophilized HDP powder under an inert atmosphere and sealed with a rubber closure and aluminium overseal. Each vial is labelled with the lot number, expiry date and storage conditions. Summary of Product Characteristics, patient information leaflet and radiopharmacy preparation instructions are provided with each carton.

Manufacturer: TechneScan HDP is a registered trademark of Curium Pharma, one of the world’s largest radiopharmaceutical manufacturers. Curium was formed in 2017 by the merger of IBA Molecular and Mallinckrodt Nuclear Medicine; earlier the product was marketed under Mallinckrodt. The product is registered in many European countries, the United States, Canada and several Asian markets.