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General Description:

Pyrithione, identified by CAS number 1121-31-9, is a notable compound with significant therapeutic applications. Pyrithione zinc, or zinc pyrithione or zinc pyridinethione, is a coordination complex consisted of pyrithione ligands chelated to zinc (2+) ions via oxygen and sulfur centers. In the crystalline state, it exists as a centrosymmetric dimer. Due to its dynamic fungistatic and bacteriostatic properties, pyrithione zinc is used to treat dandruff and seborrheic dermatitis. Dandruff is a common scalp disease affecting >40% of the world's adult population, and may be caused by fungi such as _Malassezia globosa_ and _M. restricta_ . Pyrithione zinc is commonly found as an active ingredient in OTC antidandruff topical treatments such as shampoos. It mediates its action by increasing the cellular levels of copper, and damaging iron-sulfur clusters of proteins essential for fungal metabolism and growth . Due to low solubility, pyrithione zinc released from the topical formulations is deposited and retained relatively well onto the target skin surfaces . Other uses of pyrithione zinc include additive in antifouling outdoor paints and algaecide. While its use has been approved in the early 1960's by the FDA , safety and effectiveness of pyrithione zinc has been reported for decades. It is not shown to have any significant estrogenic activity according to the _in vivo_ and _in vitro_ assays .

Indications:

This drug is primarily indicated for: Indicated for the treatment of dandruff and seborrheic dermatitis . Its use in specific medical scenarios underscores its importance in the therapeutic landscape.

Metabolism:

Pyrithione undergoes metabolic processing primarily in: After oral administration in rabbits, rats, monkeys, and dogs, pyrithione zinc is biotransformed into 2-pyridinethiol 1-oxide S-glucuronide and 2-pyridinethiol S-glucuronide . This metabolic pathway ensures efficient processing of the drug, helping to minimize potential toxicity and side effects.

Absorption:

The absorption characteristics of Pyrithione are crucial for its therapeutic efficacy: Following oral ingestion, only the pyrithione moiety is absorbed. Less than 1% of administered zinc pyrithione is absorbed from the skin . Radioabeled Zn pyrithione administered to rats, rabbits and monkeys, either orally or via intraperitoneal injection were absorbed into circulatin to extent of 80-90% . The drug's ability to rapidly penetrate into cells ensures quick onset of action.

Route of Elimination:

The elimination of Pyrithione from the body primarily occurs through: The major route of elimination from the body after oral administration in rat was urine, with S-glucuronides of 2-mercaptopyridine-N-oxide being the major metabolites and 2-mercaptopyridine-N-oxide as the minor metabolite. Following oral administration, the majority of zinc is eliminated in the feces . Upon dermal administration, >90% of recovery was obtained from washings of the application site of pigs. Urinary excretion was 3% in animals with intact skin . Understanding this pathway is essential for assessing potential drug accumulation and toxicity risks.

Pharmacodynamics:

Pyrithione exerts its therapeutic effects through: Pyrithione zinc has a broad antimicrobial spectrum of activity, including fungi, gram-positive and gram-negative bacteria . Pyrithione zinc is effective against Malassezia and all other fungi, especially the Malassezia species found on scalp . In patients with dandruff, treatment with pyrithione zinc reduced the amount of fungus on the scalp, which reduces the amount of free fatty acids, thereby reducing scalp flaking and itch . The drug's ability to modulate various physiological processes underscores its efficacy in treating specific conditions.

Mechanism of Action:

Pyrithione functions by: Inhibition of fungal growth by pyrithione zinc is linked to increased copper uptake and cellular levels of copper, which is demonstrated by decreased CTR1-lacZ expression and slightly increased CUP1-lacZ expression in affected microorganisms . The coordination complex of pyrithione zinc dissociates, and pyrithione ligand forms a CuPT complex from available extracellular copper in the target organism. Pyrithione acts as an ionophore, interacting nonspecifically with the plasma membrane to shuttle copper into the cell, and facilitates copper transport across intracellular membranes . Copper may be shuttled into the mitochondria. Copper inactivates iron-sulfur (Fe-S) cluster-containing proteins via a mechanism similar to that described for copper-induced growth inhibition in bacteria . Decreased activity of Fe-S proteins leads to inhibition of fungal metabolism and fungal growth. Pyrithione zinc has been shown to slightly increase the levels of zinc . This mechanism highlights the drug's role in inhibiting or promoting specific biological pathways, contributing to its therapeutic effects.

Toxicity:

Categories:

Pyrithione is categorized under the following therapeutic classes: Anti-Infective Agents, Anti-Infective Agents, Local, Antifungal Agents, Dermatologicals, Drugs that are Mainly Renally Excreted, Gallium Radioisotopes, Keratolytic Agents, Miscellaneous Local Anti-infectives, Sulfur Compounds. These classifications highlight the drug's diverse therapeutic applications and its importance in treating various conditions.

Experimental Properties:

Further physical and chemical characteristics of Pyrithione include:

• Water Solubility: Soluble in cold water (Zinc salt)
• Boiling Point: 100 (Zinc salt)