Final answer:
Isoflurane is the drug among the given options that is NOT a racemic mixture. It is marketed in its pure form, unlike Lignocaine, Enflurane, and Bupivacaine, which can exist as racemic mixtures.
Step-by-step explanation:
The question asks to identify which drug is NOT a racemic mixture from the given options. A racemic mixture is a 50/50 mix of two enantiomers of a chiral molecule. These enantiomers have identical physical properties except for the direction in which they rotate plane-polarized light. In pharmacology, some drugs are administered as racemic mixtures, while others are not.
Among the options provided:
- Lignocaine (also known as lidocaine) is marketed as a racemic mixture.
- Enflurane is also a racemic mixture.
- Bupivacaine is available as a racemic mixture as well as in its pure enantiomeric forms.
However, Isoflurane is not a racemic mixture but is instead marketed in its pure form. Therefore, the correct answer to the question is C. Isoflurane.