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Levamisole is used as anthelmintic agent to get rid of the intestinal worms. It is (S)-(-)-enantiomer of tetramisole. This drug is used in veterinary to treat hookworm infections.  Levamisole also finds therapeutic application in the treatment of colon cancer when given in conjunction with fluorouracil.   Chirality and biological activity Tetramisole carries one chiral stereogenic center and exists as an enantiomeric pair. The anthelmintic activity resides in the (S)-(-)-enantiomer, levamisole. The (R)- isomer harbors undesirable …

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Beta blockers, also spelled β-blockers, used as antihypertensive agents (lowering blood pressure), represent a class of chiral drugs that are marketed as racemates since the distomer exhibits no undesirable adverse effects. Three most important β-blockers viz. propranolol, atenolol, and metoprolol are marketed as racemic mixture. Chirality and biological activity β-blockers are aryloxy propanolamines with one stereogenic center and exists as a pair of enantiomers. It is observed that their therapeutic effect resides entirely in the (S)-enantiomer …

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Levodopa, L-Dopa, belong to a class of medications called dopamine agonists.  L-Dopa is used to increase dopamine concentrations in the treatment of  Parkinson’s disease. Most commonly, clinicians use levodopa as a dopamine replacement agent for the treatment of Parkinson disease. L-dopa is the precursor to dopamine and crosses the blood-brain barrier to increase dopamine neurotransmission. Chirality and Biological activity L-dopa, the (S)-enantiomer, is a chiral drug with one stereogenic center. It exists as a pair of enantiomers. The initial use …

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Indacrinone is an orally active, indanone-based loop diuretic patented by American pharmaceutical company Merck and Co as mixture of two enantiomers. In healthy volunteers, the racemic mixture of indacrinone exhibited greater natriuretic potency than furosemide, with a slower onset and longer duration of action. Furthermore, single doses of indacrinone decreased serum uric acid concentrations and increased uric acid clearance, while similar doses of furosemide generally had the opposite effects. Differences in the pharmacologic effects of …

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Levocetirizine, is chiral switch cetirizine, employed for allergies. It is a third generation, non-sedating, selective histamine H1 receptor antagonist, with antihistamine, anti-inflammatory and potential anti-angiogenic activities. Levocetirizine is used to relieve the symptoms of hay fever and hives of the skin. It is an antihistamine that works by preventing the effects of a substance called histamine, which is produced by the body.  Chirality and Biological activity Cetirizine carries one stereogenic carbon (indicted by an red arrow mark) and …

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Citalopram belongs to a class of antidepressant agents known as selective serotonin-reuptake inhibitors (SSRIs). It is indicated for the treatment of depression. Chirality and biological activity Citalopram has one stereocenter, to which a 4-fluoro phenyl group and an N, N-dimethyl-3-aminopropyl group are linked. As a consequence the molecule exists as an enantiomeric pair, the S-(+)-citalopram and R-(–)-citalopram. The selective serotonin-reuptake inhibitor  activity resides primarily in the  S-enantiomer (eutomer) while the R-enantiomer is 30-fold less potent (distomer). …

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Bupivacaine is a long acting local anesthetic in use for many years as a spinal/epidural anesthetic for childbirth and orthopedic procedures, such as hip replacement. It is marketed by AstraZeneca under the trade name Chirocaine. It acts by blocking Na+ channels and also has actions on the heart, which restrict its use by intravenous injection for regional anesthesia. Chirality and Biological activity Bupivacaine is a racemic drug. This an example where the distomer shows toxic effect …

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Chiral twins with independent therapeutic value Propoxyphene is a classical example of a synthetic chiral drug where the enantiomers of a chiral drug exhibit desirable but different therapeutic activity. Example of such biological behavior is exemplified by some of the natural products as well (e.g., quinine and quinidine) with anti-malarial and anti-arrhythmic activity. Chirality and biological activity Propoxyphene carries two stereogenic centers meaning it can exist in two pair of enantiomers (4 stereoisomers). One of …

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The chiral switches of ‘profen’ NSAIDs Chiral switches have been successful in two non-steroidal anti-inflammatory drugs (NSAIDs) – ibuprofen and ketoprofen. The switch of ibuprofen is based on chiral inversion; (±)- and (S)-ibuprofen can be viewed as being essentially bioequivalent’. Ibuprofen carries a stereogenic center in the propanoic acid side chain and exists as a pair of enantiomers. Dexibuprofen is (S)-(+)-Ibuprofen. Chiral Inversion COX inhibition resides exclusively in the (S)-enantiomer, as shown by in vitro studies …

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Salbutamol (also known as Albuterol ) is used to prevent and treat wheezing and shortness of breath caused by breathing problems (such as asthma, chronic obstructive pulmonary disease). Salbutamol is a short-acting, selective beta2-adrenergic receptor agonist used in the treatment of asthma and Chronic obstructive pulmonary disease (COPD). Synonym Albuterol Chirality and biological activity Salbutamol is formulated as a racemic mixture of the R- and S-isomers. Bronchodilator activity resides in R-(-)-Salbutamol (eutomer); S-Salbutamol (distomer) is inactive. The …

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