levorotary

The levorotary enantiomer of cetirizine, known as levocetirizine, is the more active form.

If a chiral molecule is dextrorotary, its enantiomer will be levorotary, and vice-versa.

Dextrorotary compounds have a positive specific rotation, while levorotary compounds have negative.

Therefore, methadone medications used for opiate addiction sometimes only contain levomethadone, the levorotary enantiomer.

The dextrorotary enantiomers are significantly more potent than the levorotary enantiomers, and some medications therefore only contain dexmethylphenidate.

It exists as two enantiomers: the levorotary form levamfetamine (INN) and dextrorotary form dexamfetamine (INN).

When examined in particular pharmacological assays for psychomotor stimulant-like activity, both the dextrorotary and levorotary enantiomeric forms of methcathinone hydrochloride have been found to be pharmacologically active.

In some cases the (R)-enantiomer is the dextrorotary enantiomer, and in other cases the (R)-enantiomer is the levorotary enantiomer.

Both the dextrorotary and levorotary enantiomers displayed receptor affinity for the serotonergic 5HT and 5HT subtypes, though direct binding to the serotonin transporter was not observed.

If there is a pair of enantiomers, each with one stereocenter, then one enantiomer is R and the other is S, and likewise one enantiomer is levorotary and the other is dextrorotary.

It is obtained by hydrolysis of cocaine with acids or alkalis, and crystallizes with one molecule of water, the crystals melting at 198-199 C. It is levorotary, and on warming with alkalis gives iso-ecgonine, which is dextrorotary.