Racemic Mixture - Racemic Pharmaceuticals

Racemic Pharmaceuticals

Some drug molecules are chiral, and the enantiomers have different effects on biological entities. They can be sold as one enantiomer or as a racemic mixture. Examples include thalidomide, ibuprofen, and salbutamol. Adderall is a mixture of several different amphetamine enantiomers. A single amphetamine dose combines the neutral sulfate salts of dextroamphetamine and amphetamine, with the dextro isomer of amphetamine saccharate and D/L-amphetamine aspartate monohydrate. The prescription analgesic tramadol is also a racemate.

In some cases (e.g., ibuprofen and thalidomide), the enantiomers interconvert or racemize in vivo. This means that preparing a pure enantiomer for medication is largely pointless. However, sometimes samples containing pure enantiomers may be made and sold at a higher cost in cases where the use requires specifically one isomer (e.g., for a stereospecific reagent); compare omeprazole and esomeprazole.

While often only one enantiomer of the drug may be active, in cases like salbutamol and thalidomide, the other enantiomer may be harmful. The (R) enantiomer of thalidomide is effective against morning sickness, while the (S) enantiomer is teratogenic, causing birth defects. Since the drug racemizes, the drug cannot be considered safe for use by women of child-bearing age, and its use is tightly controlled when used for treating other illness.

Methamphetamine is available by prescription under the brand name Desoxyn. The active component of Desoxyn is dextromethamphetamine hydrochloride. This is the right-hand isomer of methamphetamine. The left-handed isomer of methamphetamine, levomethamphetamine, is an OTC drug that is less centrally-acting and more peripherally-acting.11