Technetium-99m Labelled Kit Preparation Flashcards
Non-radioactive pharmaceutical products that are intended for radiolabeling
cold kits
intended for direct radiolabeling
cold kits
Direct incorporation of the metal to the chelator causing it to become a fully functional diagnostic or therapeutic radiopharmaceutical
end product of cold kits
add the radionuclide to the vial and mix it in the presence/absence of heat for a long/short period of time
direct radiolabeling
General components of Tc99m cold kits
- Ligand / complexing agent / chelating agent
- Reducing agent/s
- Antioxidant/s
- Catalyst/s
- pH adjusters (single pH adjusting agent or pH buffer systems)
- Tonicity adjusters
- Fillers
- Blanketing / purging agent
Acts as the chelator for the metal present in the other solution, which is the eluate of the generator (general purpose)
Ligand
reduce the oxidation state of technetium (from +7 to +5, +4 or +3) for it to be more favorable that will participate in the reaction
reducing agents
prevent the oxidation and scavenge the free radicals
antioxidants
speed up the formation of the complex (without this it will be slow or not working at all)
catalyst
involved in causing the formation of the Tc-Sn colloid and TcO2
pH adjusters
adjust the concentration of the salt solution to be compatible with our bodily fluids
Tonicity adjusters
also called as bulking agents
Fillers
facilitate the solution and will not clump together but will be dispersed across the matrix of the filler
Fillers
remove the oxygen present in the vial because the oxygen oxidizes or speed up the formation of stannic ion which are not desirable because it will reduce the efficacy of the stannous ion in producing the pertechnetate
Blanketing
gases nitrogen and argon
inert gases
it cannot introduce air because you would want to remove the oxygen present in the vial. Therefore, you need to completely eliminate the presence of oxygen. You need to replace it with a denser gas such as argon or nitrogen gas
Blanketing
▪ Effective reduction at mild conditions (neutral to weakly acidic
conditions, absence of toxic substances, labeling at room
temperature)
▪ Formation of a single component complex with a distinct
oxidation state
▪ No interference with the complexation process
▪ Not included in the final complex
▪ Stable during storage of the kit (long shelf life)
Ideal Reducing agent:
it reduces the oxidation state to a more favorable one that will participate in the complexation reaction
Reducing agents
what is the normal working range of Tc radiolabeling
5-7
why is pH 6 is better?
because at pH 7, the rate of hydrolysis increases. you need to reduce the pH to more acidic than neutral
what oxidation state does Tc exist in formation of a single component complex with a distinct oxidation state
-1 to +7
normal oxidation state of Tc
+4
can you use another reducing agent that may participate
in the complexation reaction?
no
is citrate a reducing agent?
no, it only participates in complexation reaction
Stable during storage of the kit (long shelf life)
something that is very reactive
for example, you add a metal magnesium. Metal
magnesium is very active when in the presence of air, so when you have a Mg in the presence of air it forms magnesium oxide and then MgO it reduces the amount of metallic Mg. Therefore, the shelf life of magnesium metal decreases because it readily reacts with presence of oxygen in the air
Stable during storage of the kit (long shelf life)
what is the most well known Tc99m reducing agents
Stannous salts
what is the most used stannous salt?
Tin (II) chloride
Stannous salts are (non-toxic toxic) and (unstable or stable) when lyophilized and kept in a nitrogen atmosphere
non-toxic and stable
The amount of stannous chloride is empirically optimized for each kit to balance between the two parameters: what are the two
a. Completely reducing pertechnetate From Tc (VII) to Tc (IV)
b. Avoid reducing pertechnetate From Tc (VII) to lower oxidation states
what happens if you add more Tc+4?
you reduce the radiolabeling efficiency for that kind of radiopharmaceutical
what is the ratio
1 million : 1
what certain situations wherein the amount of reacting stannous ion must be controlled
a. wherein the metal exists in multiple oxidation states are favored with a certain ligand
b.when hydrolysis products interfere with complex stability
what limits the release of stannous ion into the solution
The use of:
Tin (II) tartrate
Tin (II) gluconate
Tin (II) citrate
Tin (II) EDTA etc.
Under certain pH conditions, Stannous chloride is not soluble in water. But in acidic pH, they are soluble or insoluble?
soluble
Direct labeling of proteins
stannous chloride is administered for “pre-tinning”
incubating the protein with stannous ion, reactive disulfide bonds are reduced in addition to pertechnetate
pre-tinning
just deactivate all sites of the protein before you label it with Tc +4
pre-tinning
if it is said that it is just based on 370 MBq or 10 mCi, when you have higher activity, what should happen to the Tin content?
increase
Issues with using Stannous ion
- Stannous compounds are difficult to purify; they contain at least 5% Sn (IV) →Sn (IV) is an unavoidable, relatively concentrated impurity in radiopharmaceutical preparations
- Stannous ion is readily oxidized by various oxidants such as oxidant in the air (oxidation proceeds already on standing)
- The amount of cumulative Tc-99 exceeds the reductive capacity of tin
- During the reduction of pertechnetate, tin is oxidized and hydrolyzed to highly poly-dispersed colloidal particles (only occurs if there are weak and unsuitable ligands present in 99mTc labeling)
is an unavoidable, relatively concentrated impurity in radiopharmaceutical preparations
Sn (IV)
what percentage of Sn (IV) stannous compounds contain?
at least 5%
During the reduction of pertechnetate, tin is oxidized and hydrolyzed to ???
highly poly-dispersed colloidal particles
Therefore, the addition of tartrate ___ the probability that it will go to completion, as compared to Tc+4 and MAG3 alone
increases
In the presence of the tartrate salt: high or low amount of Tc4+ concentration
high
In the absence of the tartrate salt: high or low amount of Tc4+ concentration
low
Possible ways on how to address issues with Stannous chloride
- Use of other stannous salts such as stannous fluoride, oxalate, tartrate, citrate and phosphates
- Fixing of stannous ion to an ion exchange resin
what are the stannous salts used to address issues with stannous chloride?
stannous fluoride, oxalate, tartrate, citrate and phosphates
Added to the formulation to increase the stability of the radiopharmaceutical
Antioxidants
they can serve as scavengers. they scavenge the free radicals formed when the Tc99m interacts with water to form indirect radiolytic product
Antioxidants
Commonly used Antioxidants in Tc99m radiopharmaceutical kits
- Ascorbic acid
- Gentisic acid
- P-aminobenzoic acid
Substance that participates in a ligand exchange reactions
Catalyst
Used when complex formation with a certain ligand is slow relative to formation of reduced hydrolyzed technetium
Catalyst
Examples of catalysts
EDTA
Gluconate
Citrate
Another term for Fillers
Bulky regions
added to achieve rapid solubilization of the vial components through the control of particle size during the lyophilization process
Fillers
prevent the clumping of certain ingredients because there are certain ingredients that are hard to disperse when clumped together
Fillers
Examples of Fillers
Sodium chloride in HMPAO kits (although sodium chloride is
generally used as a tonicity adjuster)
Mannitol in MIBI kits
What is an isotonic solution?
0.9 % w/v Na (whatever you will put inside the vial, as long as the total equivalent is 0.9g per 100mL)
To ensure that the radiolabeling process will proceed at the right pH
pH adjusting agent
Single or buffer: Hydrochloric acid and Sodium hydroxide
Single pH adjusting agents
Single or buffer:
Na3PO4 + Na2HPO4
Citric acid + sodium citrate
pH buffers
combination of two salts
pH buffers
dibasic + monobasic phosphate = ???
nearly neutral
It involves drying of frozen materials by sublimation
Lyophilization (freeze drying)
Prolongs shelf-life of food and pharmaceutical products
Lyophilization (freeze drying)
It depends on the storage conditions, leak-proof of the packaging material, and the inherent stability of the cold kit formulation
Lyophilization (freeze drying)
in cold kits, lyophilization prolongs the shelf life by how many years average?
1 year average
At 1 atm, it is not possible to sublime ice. Therefore you have to reduce the pressure to _____ for it to be able to participate in the transition between the ice and steam.
the vacuum pressure
In lyophilization, you need to make the pressure ____
at least 0.004 atm
The more efficient the sublimation process is, the less water retained in the kit.
Therefore, the longer the shelf life of the cold kit.
ice to steam
sublimation
steam to ice
deposition
to get the 1 year average, it must be stored in how many degrees celsius?
2-8 deg celsius
In Lyophilization, why is increasing the temp to 30 deg C not be favorable for the cold kit any more?
because the higher the temperature the more reactive the ingredients are allowing it to become 2, 3 or 6 months old (shorter shelf life)
it ensures that the inert gas will not be exchanging with oxygen in the air, to prevent the cold kit from getting oxidized
leak-proofing
such as when you have a Stannous fluoride which is inherently unstable in the presence of air, unlike when you add HCl or NaCl. These are not really reacting in the presence of oxygen
inherent stability of the cold kit formulation
Advantages of lyophilization
- Chemical, bacterial or enzymatic changes do not
easily occur (prevents souring) - Sterility is more guaranteed
- Transportation is easier
Disadvantages of lyophilization
- Reentry of moisture may destroy the products (there is instability)
- Direct optical control cannot be performed (high tendency to have particulate contaminants)
General lyophilization cycle
Freezing, primary drying, secondary drying
-30 to -80 °C atm, 24-36h
Freezing
-30 to -80 °C vacuum, 24-36h
primary drying
15 to 25°C vacuum, 24-36h
secondary drying
you have to freeze it completely, otherwise, when you have a mixture of ice and water, when you apply vacuum your water will pop out and destroy the product
Freezing
remove the crystalline ice from the kit
Primary drying
remove any residual moisture present when you increase the temperature to its intended transport conditions
Secondary drying
Final process of Lyophilization cycle
Purging / backfilling
Stoppering
Crimping
15-25°C atm Purged with N2
Purging / backfilling
Aspect of quality management system that ensures that medicinal products are consistently produced and controlled to the quality standards appropriate to their intended use and as required by their marketing authorization
Good manufacturing practices
Premises Equipment Production Quality Control
Materials (RM/PM/FP/etc.) Sanitation Complaints
Personnel Documentation Qualification and Validation
Product recall Audits Quality Assurance System
Components of good manufacturing practices
(for commercial manufacturers)
Raw material quality
Process aid quality
Chemical impurities
Aseptic conditions
Aseptic techniques
Microbiological impurities
Manual radiolabeling
Synthesis procedures
Radiochemical impurities
Reactor and cyclotron production
Generator quality
Radionuclidic impurities
absence of viable microorganisms
Sterility
the probability of a single viable microorganism occurring in or on a product after sterilization
Sterility assurance level (SAL)
Acceptable SAL is ?
minimum of 10-6
SAL meaning
sterility assurance level
How do you interpret 10-6 in simple words?
For every 1,000,000 sterilized units, 1 unit remains non-sterile
the process that destroys or eliminates all viable microorganisms
Sterilization
3 sterilization methods
physical, chemical, radiation
what are the physical sterilization methods?
steam sterilization
dry heat sterilization
sterile filtration
what are the radiation sterilization methods?
Ionizing (electron beam, gamma)
Non-ionizing (UV)
what are the chemical sterilization methods?
Liquid sterilization (alcohols)
Gas sterilization (EtO)
ONLY ACCEPTABLE TERMINAL STERILIZATION METHODS
steam dry heat, ionizing radiation
Removal of microorganisms using a bacterial retentive filter to produce a sterile filtrate
Sterile filtration
_____ is NOT a terminal sterilization technique
Aseptic filtration
size of the filter in the COW
0.2 um
Manufacturing process where all materials including raw materials, equipment, process aids, and packaging materials are first subjected to sterilization separately then processed together in an extremely high quality environment (called a “cleanroom”) that is constantly monitored for air quality and microbial contamination
Aseptic processing
extremely high quality environment in aseptic processing
cleanroom
For radiolabeling of Technetium- 99m kits, the diluent used is ???
sterile NSS (normal saline solution)
WFI may be used IF AND ONLY IF:
- The information on isotonicity of the cold kit is available
- If specified in the product insert
what is WFI
water for injection - the purest grade of pharmaceutical bulk water
For most common Tc99m radiopharmaceuticals, incubation takes place at ____ temp and _____ incubation time
room temperature and there is minimal incubation time
Exceptions in incubation
those that employ heating which is done under boiling water bath (e.g., [99mTc]sestamibi, [99mTc]MAG3, [99mTc]sulfur colloid)
