Mercaptopurine (CAS 50-44-2): storage and disposal
Pharmacy cupboards hold mercaptopurine as tablets, normally in a ward or outpatient dispensary where it is dispensed to patients over long periods. The classification is a single statement, toxic if swallowed, but it is also handled as a cytotoxic medicine, which matters when tablets are loose, returned or dropped. The pure compound is a yellow crystalline powder, and the yellow colour is a clue worth knowing if powder escapes a pack.
- CAS number
- 50-44-2
- Form
- Solid
- Storage class
- Toxic
- Signal word
- Danger
- Usual EWC code, laboratory stock
- 16 05 06*
Acute toxicity
What to do this week
- Without moving anything that looks damaged, check the label is readable and write down the opened date if it is not already there.
- Check it is stored as toxic stock, and apart from anything listed under "Do not store with" on this page. If nothing is listed, that does not prove it is safe with everything.
- If you no longer need it, add it to your disposal list so it can be included in a collection.
Safe storage in a school or lab
Oral toxicity decides where it goes: a locked cabinet with a stock record, away from food and drink areas and apart from incompatible chemicals, including oxidising chemicals and strong acids, following the product's storage requirements. Tablets should stay in their original bottles or blister packs so the label shows the strength and batch. Keep returned packs on a separate shelf from dispensable stock. If a bottle has spilled loose tablets, keep the affected stock out of use and report the spill to the pharmacy or laboratory safety lead. Trained personnel should follow the site's cytotoxic medicines procedure for recovering and containing the tablets. Record the affected material for specialist collection.
How to tell it has deteriorated
Yellow dusting inside a bottle or blister is the first thing to look for, because the powder is yellow and shows against pale packaging. Beyond that, check for crumbling tablets, tablets stuck together, damp marks, lifted foil and a label that has faded or lost its batch. No other chemical signs can be stated with confidence for this substance. Packs returned by patients, or with no date, should be treated as expired, because the history of the contents is unknown.
How it is disposed of
We arrange this by specialist collection. We do not publish a drain or general waste route for any chemical. It is normally packed in a toxic laboratory pack with compatible chemicals.
Recording matters more than the volume here: tablets, returned packs and any loose tablets recovered from spills are listed separately, with counts and strengths where the label shows them. Pouring tablets out, crushing them or putting them down a sink or in the general bin is not allowed. Healthcare sites normally use 18 01 08* for this kind of medicine. The item can be quoted online, but a manual enquiry is the right route if the packs are damaged or the history is unknown.
| Usual EWC code, laboratory stock | 16 05 06* |
|---|---|
| Discarded organic chemical, not a laboratory pack | 16 05 08* |
| Human healthcare setting | 18 01 08* |
| Usually classed as hazardous waste | Yes |
The code depends on where the waste came from and what it contains, and classifying it is the producer's duty. Use the waste code finder to see why.
Do not store with
- OxidiserToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
- AcidToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
Named chemicals to keep apart
- Acetic acidToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
- Calcium hypochloriteToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
- Hydrochloric acidToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
- Hydrogen peroxideToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
- Nitric acidToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
- Potassium nitrateToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
- Potassium permanganateToxic and oxidising stock are stored apart. A reaction could release toxic vapours.
- Sulfuric acidToxic stock is stored apart from acids. Several toxic salts release toxic gas in contact with acid.
Common quantities
Usually held as: tablets.
Tell us the container size and how many you hold. An estimate is enough to start with, and some items cannot be priced until someone has looked at them.
Where it is commonly held
Hazard statements
- H301 Toxic if swallowed.
Precautionary statements
- P203 Obtain, read and follow all safety instructions before use.
- P264 Wash hands and exposed skin thoroughly after handling.
- P270 Do not eat, drink or smoke when using this product.
- P280 Wear protective gloves, protective clothing, eye protection and face protection.
- P301+P316 IF SWALLOWED: Get emergency medical help immediately.
- P301+P317 IF SWALLOWED: Get medical help.
- P318 If exposed or concerned, get medical advice.
- P321 Specific treatment (see supplemental first aid instruction on this label).
- P330 Rinse mouth.
- P405 Store locked up.
- P501 Dispose of contents and container in accordance with local, regional, national and international regulations.
Substance as classified, dilutions may differ.
Questions
What does yellow powder in a mercaptopurine bottle mean?
The compound is a yellow crystalline powder, so yellow dust suggests tablets are crumbling or have been disturbed. Do not shake or open the bottle. Record it as damaged stock and include it in the disposal list.
Can we put returned mercaptopurine tablets back in stock?
No. Returned packs have unknown storage history and are treated as unwanted stock. Keep them on a separate shelf in a labelled container and include them in the collection request.
Is mercaptopurine quoted online?
It can be, because the classification is a single oral toxicity statement. If packs are damaged, mixed or undated, send a manual enquiry instead so the collector knows what to expect.
Where should mercaptopurine be kept in a pharmacy?
In a locked cabinet with a stock record, away from food and drink and apart from oxidising stock and acids. Keep tablets in their original packs and returned packs on a separate shelf.
