1. D6 Environmental impact of some medications
Medicinal Chemistry

2. Nuclear waste
Radioactive isotopes are used for diagnose and treatment.
Radioactive isotopes decay and emit alpha, beta and gamma radiations
These radiation form ions by ejecting electrons out of matter and in this way damage DNA.

3. Radioactive isotopes used Medical
131I, used to treat thyroid cancer, has a half-life of just 8 days.
60Co, used to treat other forms of cancer, has a half-life of 5.3 years.

4. Types of Radioactive waste
Low Level Waste
High level waste
Low-level waste has a low activity (not many radioactive nuclei decay each second to produce ionising radiation) and usually contains isotopes with short half-lives (ionising radiation is given off for a shorter period of time).
High-level waste has a high activity (many radioactive nuclei decay each second to produce ionising radiation) and usually contains isotopes with longer half-lives (ionising radiation is given off for a long time

5. Disposing off Radioactive waste
Radioactive materials have the potential to be a serious hazard both to people and to the environment – therefore the disposal of medical nuclear waste must be controlled carefully.
Governments set strict limits on the release of radioactivity into the environment and monitoring is essential to ensure that these regulations are adhered to.
The main approaches to the disposal of nuclear waste are ‘dilute and disperse’, ‘delay and decay’ or ‘confine and contain’. ‘Confine and contain’ is always used for nuclear waste that has a high level of activity.

6. Low-level waste- Source
This includes items that have been contaminated with radioactive material or have been exposed to radioactivity.
Examples are gloves and other protective clothing, tools, syringes and excreta from patients treated with radioisotopes.

7. Low-level waste- disposal
Stored until it is safe to dispose as ordinary waste
Some low level waste is diluted and dispersed
High activity low level waste is buried underground. e.g. some wastes are buried in special concrete containers for a period of 500 years

8. High level Waste- Source
This includes spent fuel rods and other materials from nuclear reactors.
High-level waste will remain hazardous to humans and other living things for thousands of years.

9. High level Waste- Disposal
High level liquid waste is first is converted to glass (vitrification) for making storage easier.
High level waste is first kept underwater for cooling from nine month to 10 years.
After cooling waste is transferred to casks (Special storage tank made of steel and concrete)
The dry casks are stored in bankers for thousand years.

10. Issue
Permanent storage of high-level radioactive waste is a major problem and various solutions have been suggested – such as burying the waste deep underground in stable geological areas. Over thousands of years, however, it is difficult to predict what processes could occur to cause release of the radioactive material. Many people argue that there is no suitable solution for the disposal of high-level waste.

11. The release of antibiotics into the environment
Antibiotics can enter the water supply by several routes. These include:
incorrect disposal of unwanted medicines – for example, by flushing old medicines down the toilet.
agriculture – drugs given to animals will be present in animal waste (urine and feces) and can find their way into groundwater, rivers and lakes. Treating water to produce drinking water does remove some of these

12. Concern
The release of antibiotics into the environment is regarded as a particular problem because not only can they cause damage to aquatic organisms, but they can also result in increased resistance of bacteria to antibiotics. Antibiotics (antibacterials) are used to treat a variety of conditions but if bacteria develop resistance to antibiotics such as penicillin, these diseases can become much more difficult to cure.

13. Green chemistry
Green chemistry (or sustainable chemistry) is an approach to chemical research and chemical industrial processes that seeks to minimize the production of hazardous substances and their release into the environment.

14. The best synthetic routes to a drug:
use readily available and safe materials
have the minimum number of steps
convert as much of the starting materials as possible into the required product at each step – good atom economy and good yield
use as little solvent as possible
use as little energy as possible.
An important consideration in green chemistry is the concept of atom economy

15. Drug design and Atom economy
Atom economy can be used as a measure of how efficient a particular reaction is in terms of converting as much of the starting materials as possible into useful products.

16. Synthesis of oseltamivir- Moving toward greener drug design
Oseltamivir has been discussed earlier as a treatment for influenza.
Total synthesis (from petrochemical starting materials) of oseltamivir involves huge amounts of materials and can generate thousands of kilograms of waste per mole of oseltamivir made.
Therefore it was essential to develop greener routes to the drug.

17. Efforts
The current commercial synthetic route uses a naturally occurring material, shikimic acid, as the starting material – this cuts out several steps in the synthesis and makes it greener. Shikimic acid is a renewable material that can either be extracted from Chinese star anise or obtained from glucose by fermentation using genetically modified bacteria.
Even starting from shikimic acid, a further ten steps are required to make oseltamivir, so more work is required to make this synthesis even greener!

18. Although shikimic acid can be obtained from star anise, this in itself causes a problem – the yield is not very high and the production of shikimic acid is linked to the availability of star anise. The use of GM bacteria is likely to provide a better long-term solution to producing shikimic acid – fermentation uses relatively low temperatures and an aqueous medium, so it is a reasonably green process.

19. Solvent Waste
As most of the medicinal products are prepared in organic solvents.
Solvents contribute 80 to 90 % by mass of medicinal products.
These solvents are mostly toxic and hazardous for environment.

20. Solvent Waste
First step in making process greener is to find an environment friendly solvent.
If a greener solvent cannot be found then the amount used should be reduced as far as possible.
The next consideration is the possibility of a solvent being recycled and reused.
If the solvent cannot be reused, then it must be disposed of as safely as possible.