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Pentamidine, sold under the trade name Pentam 300 for injection and Nebupent for oral inhalation, is an antimicrobial medication given to prevent and treat pneumocystis pneumonia (PCP) caused by Pneumocystis jirovecii, a severe interstitial type of pneumonia often seen in people with immune system problems, including those with human immunodeficiency virus (HIV) infection. The drug is also the mainstay of treatment for stage I infection with Trypanosoma brucei gambiense (West African trypanosomiasis) and can also be used to treat infections caused by Leishmania and Babesia.

Common side effects for the injection include nausea, vomiting, diarrhea, loss of appetite, unusual taste, dry mouth, dizziness, and irritation in the injection site. For inhaled pentamidine, common side effects include bronchospasm, increased serum creatinine, cough, and low blood sugar levels. To date, it is uncertain whether taking pentamidine while pregnant or breastfeeding is safe. Not enough data currently exists to determine whether dosages should be changed for kidney and liver impairment.

Pentamidine was first used to treat Trypanosomiasis in 1937 and Leishmaniasis in 1940 before it was registered as pentamidine mesylate in 1950. Its efficacy against Pneumocystis jirovecii was demonstrated in 1987, following its re-emergence on the drug market in 1984 in the current isethionate form. Generic drug versions are currently available. In the US, APP Pharmaceuticals sells pentamidine under the trade name Pentam 300 for injection and Nebupent for oral inhalation. As of 2016, brand name Nebupent inhalation powder costs 122.84 USD, brand name Pentam 300 injection vial costs 94.8 USD, and generic pentamidine 300 mg vial costs 45.31 USD. It is on the World Health Organization's List of Essential Medicines, the most important medications needed in a basic health system.

Mechanism of action
The mechanism seems to vary with different organisms and is not well understood. However, pentamidine is suspected to work through various methods of interference of critical functions in DNA, RNA, phospholipid and protein synthesis.[13][14] Pentamidine binds to adenine-thymine-rich regions of the Trypanosoma parasite DNA, forming a cross-link between two adenines four to five base pairs apart. The drug also inhibits topoisomerase enzymes in the mitochondria of Pneumocystis jirovecii. Similarly, pentamidine inhibits type II topoisomerase in the mitochondria of the Trypanosoma parasite, resulting in breaks and unraveling it's circular mitochondrial DNA.

Resistance
Strains of the Trypanosoma brucei parasite that are resistant to pentamidine have been discovered. Pentamidine is brought into the mitochondria through carriers, and the absence of these carriers prevents the drug from reaching its site of action.

Pharmacokinetics
Absorption: Pentamidine is completely absorbed when given intravenously or intramuscularly. When inhaled through a nebulizer, pentamidine accumulates in the bronchoalveolar lavage fluid of the lungs at a higher concentration compared to injections. The inhaled form is minimally absorbed in the blood. Absorption is unreliable when given orally.

Distribution: When injected, pentamidine binds to tissues and proteins in the plasma. It accumulates in the kidney, liver, lungs, pancreas, spleen, and adrenal glands. Additionally, pentamidine does not reach curative levels in the cerebrospinal fluid. Inhaled pentamidine is mainly deposited into the bronchoalveolar lavage fluid of the lungs.

Metabolism: Up to 12% of pentamidine is eliminated in the urine unchanged.

Elimination: Pentamidine has an average half-life of 5-8 hours when given intravenously and 7-11 hours when given intramuscularly. However, these may increase with severe kidney problems.

Chemistry
Pentamidine isethionate for injection is commercially available as a lypophilized, white crystalline powder for reconstitution with sterile water or 5% Dextrose. After reconstitution, the mixture should be free from discoloration and precipitation. Reconstitution with sodium chloride should be avoided due to formation of precipitates. Intravenous solutions of pentamidine can be mixed with some other intravenous HIV medications like zidovidine and intravenous heart medications like diltiazem. However, intravenous solutions of antiviral foscarnet and antifungal fluconazole are incompatible with pentamidine. To avoid side-effects associated with intravenous administration, the solution should be slowly infused to minimize the release of histamine.

Brand names and dose forms

 * For oral inhalation and for nebulizer use:
 * NebuPent Nebulizer (APP Pharmaceuticals LLC - US)


 * For intravenous and intramuscular treatment:
 * US and Canada:
 * Pentacarinat 300 injection powder 300 mg vial (Avantis Pharma Inc - Canada)
 * Pentam 300 (APP Pharmaceuticals LLC - US)
 * Pentamidine isethionate 300 mg for injection (David Bull Laboratories LTD - Canada, Hospira Healthcare Corporation - Canada)
 * International Brands:
 * Pentamidine isethionate (Abbott)
 * Pentacarinat (Sanofi-Aventis)
 * Pentacrinat (Abbott)
 * Pentam (Abbott)
 * Pneumopent