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Radiopharmaceuticals
See also Thorotrast
General information
Radioactive substances may be used in medicine as tracers, the quantities used in this case being merely sufficient to enable them to be detected, or as therapeutic agents, in which case the quantities employed and the amount of radiation emitted may be considerable. Risks resulting from the radiation itself fall outside the scope of this volume.
Radio-iodine is covered in a separate monograph.
General adverse effects and adverse reactions
Radiopharmaceuticals have a good safety record. The prevalence of adverse reactions is approximately 1000-fold than less than that occurring with iodinated contrast media and drugs. The Society of Nuclear Medicine has maintained a register of adverse reactions to radiopharmaceuticals occurring in USA since 1976. The frequency of reactions appears to be falling because of improved quality control of radiopharmaceuticals. Many of the earlier adverse reactions were attributed to iron-containing formulations, gelatin-stabilized formulations, materials such as albumin contaminated with pyrogens, and other products no longer in use. The overall incidence of reactions for the year 1978 was estimated to be 1–6 per 100 000 examinations [ ].
In order to determine the prevalence of adverse reactions to radiopharmaceuticals, a 5-year prospective study (1989–94) was performed in 18 institutions in the USA [ ]. The reported incidence rate was 0.0023%. No adverse reaction required hospitalization or had significant sequelae. The adverse reactions and types of radiopharmaceuticals are shown in Table 1 .
Table 1
Adverse reactions to 783 525 radiopharmaceutical doses in 1989–94 in the USA (n = 18)
| Radiopharmaceutical | Adverse reaction | Number |
|---|---|---|
| 67 Gallium citrate | Rash | 1 |
| [ 131 I] Iobenguane (MIBG) | Chest discomfort, light-headedness | 1 |
| 99m Tc-macroaggregated albumin | Rash | 1 |
| 99m Tc-medronate (MDP) | Rash/nausea/mild anaphylaxis | 2/1/1 |
| 99m Tc-oxidronate (HDP) | Rash/sweating | 4/1 |
| 99m Tc-pentetate (DTPA) | Rash | 1 |
| 99m Tc-sestamibi | Rash | 1 |
| 99m Tc-sulfur colloid | Nausea, vomiting, rash, headache | 1 |
| Stannous pyrophosphate (non-radioactive) * | Mild anaphylaxis/light-headedness | 2/1 |
* Given intravenously to allow in vivo radiolabeling of erythrocytes and considered part of the final radiopharmaceutical.
Another study was undertaken to determine the prevalence of adverse reactions to positron-emitting radiopharmaceuticals through a prospective 4-year study in 22 institutions. PET radiopharmaceuticals have an excellent safety record because no adverse reactions were reported in over 80 000 administered doses in this study [ ].
In a review of UK reports of adverse reactions to radiopharmaceuticals from 1977 to 1983, there was a changing distribution pattern with time ( Table 2 ) [ ]. This was partly due to elimination of some of the earlier, more toxic formulations and partly due to changing usage, more particularly the increased use of phosphonate formulations. The authors estimated that only 10% of reactions were reported and that the probable incidence rate was between one in 1000 and one in 10 000. There was one death associated with a hypotensive reaction to colloid in a severely ill patient. One elderly patient had a cardiac arrest after injection of macro-aggregated albumin but was resuscitated. In a European prospective survey during 1996, there was a prevalence of 11 events per 105 administrations of radio-pharmaceuticals. No serious or life-threatening events were reported [ ].
Table 2
Major groupings of adverse reactions to radiopharmaceuticals reported in the UK from January 1977 to December 1983
| Period | Colloids | Phosphonates | Albumin particulates | Others |
|---|---|---|---|---|
| 1977 to mid-1980 | 12 (48%) | 2 (8%) | 5* (16%) | 8* (28%) |
| Mid-1980 to 1983 | 8 † (21%) | 15 † (45%) | 3 (10%) | 8* (24%) |
| Total | 20 † (33%) | 17 † (28%) | 8* (13%) | 16* (26%) |
*1 case or † 2 cases considered to be “unlikely to be due to the radiopharmaceutical”.
99m Technetium
The widespread use of 99m Tc-diethylaminetriaminepenta-acetate (DTPA), mostly used for renal imaging, has brought with it a number of reported DTPA adverse reactions. Typical symptoms include low pressure, loss of consciousness, feeling faint and occasionally rashes and bronchospasm. In Europe, a patient with a history of asthma developed severe bronchospasm and died within a matter of minutes [ ]. A series of very serious problem developed following intrathecal injection of 99m Tc-DTPA in what turned out to be, strictly speaking, a misformulation incident. Almost all currently used DTPA formulations contain the mixed calcium/sodium salt of DTPA. However, one particular manufacturer used the trisodium salt. This form is capable of chelation of cerebrospinal fluid calcium and magnesium and causing gradual onset of severe neurological signs and severe paresthesia [ ].
99m Tc-labeled serum albumin microspheres have in one case caused collapse, apparently because the patient in question had earlier been sensitized by blood transfusions [ ].
A case of anaphylaxis occurred after the injection of a leukocyte suspension labeled with 99m Tc-hexamethyl propylene amine oxime [ ].
Inhalation of Technigas (an ultrafine suspension of 99m Tc-labeled carbon particles) for ventilation scintigraphy, in a series of patients led to a temporary reduction in oxygenation in 87% of cases, often in sufficient degree to cause some discomfort [ ]. Injection of 99m Tc-MAA for perfusion scintigraphy similarly tended to cause a decrease in oxygenation, but insufficient to cause symptoms.
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