Industry

Pharmaceutical (Stereochemistry)

- Enantiomers have different effect on human bodies

- One enantiomer is more effective than the other

- One enantiomer is useful, while the other causes harm

Particular significance is given to stereochemistry in the pharmaceutical sector. This is seen by the different results that enantiomerism in pharmacological goods yields.

1. Enantiomers that have different effects on the human body

Let's start by examining propoxyphene. The human body reacts differently to the two enantiomers, dextropropoxyphene and levopropoxyphene, since they are specific to distinct receptors. Darvon, or dextropropoxyphene, is a medication used to relieve pain that is marketed as an analgesic. On the other hand, levopropoxyphene which was originally sold as Novrad has a different pharmocological impact. It relieves coughing by acting as an antitussive. 

Methorphan's enantiomers also exhibit diverse toxicological and pharmacological properties. Since dextromethorphan interferes with the brain signals that cause the cough reflex, it is a popular antitussive found in many over-the-counter cough and cold remedies. Conversely, lexromethorphan is an opioid analgesic that belongs to the morphinan family and has never been commercialised. It has morphine-like effects via binding to opioid receptors.

2. Enantiomers that are more effective than the other

Let us now have a look at the varied effectiveness of the ibuprofen enantiomers. A non-steroidal anti-inflammatory medication called ibuprofen is used to treat ailments like headaches and muscle aches. Both the R(-) and S(+) enantiomers of ibuprofen are known to exist. S-ibuprofen is more successful at inducing a reaction than R-ibuprofen because it is a more strong inhibitor of the cyclooxygenase. 

Ibuprofen is marketed as a racemic combination of S(+) and R(-) ibuprofen. Ibuprofen is more effective in relieving pain from inflammations because the body converts roughly 40–60% of R(-) ibuprofen into S(+) ibuprofen in the digestive tract after consumption. 

However, the transformation of R(-) ibuprofen into S(+) ibuprofen may cause a delay in the commencement of pharmacological activity, and determining the ideal dosage of the medication may present challenges. Thus, it would be preferable to have a single-enantiomer medication that exclusively contains the S(+) ibuprofen enantiomer in order to prevent this from occurring.

3. Enantiomers that are both harmful and useful

Were you aware that there is a drug that can cure you, but it can also kill you? The name of this notorious medication is thalidomide! Thalidomide was first prescribed as a sedative and hypnotic in Germany in 1957. It was mostly sold over-the-counter to relieve morning sickness in expectant mothers, which was a beneficial application for the medication. But throughout the next few years, when pregnant women continued to use the medicine, roughly 10,000 babies were born with limb malformations, or phocomelia, all across the world. Of the children who survived, only half had deformities other than deformities of the limbs.

How could two radically different outcomes from the same medicine occur? Well, the fact that thalidomide is a racemic mixture of (R)- and (S)-enantiomers is the exact source of the awful side effects.

While the (S)-isomer is teratogenic and may have a deleterious effect on the development of the embryo or foetus, the (R)-enantiomer has sedative properties. It is useless to separate the isomers before usage because they interconvert under biological circumstances. Following the thalidomide debacle, numerous nations started to impose stricter guidelines for drug approval