Pentamidine

Pentamidine is an antimicrobial medication used to treat African trypanosomiasis, leishmaniasis, Balamuthia infections,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> babesiosis, and to prevent and treat pneumocystis pneumonia (PCP) in people with poor immune function.<ref name=AHFS2016/> In African trypanosomiasis it is used for early disease before central nervous system involvement, as a second line option to suramin.<ref name=AHFS2016/> It is an option for both visceral leishmaniasis and cutaneous leishmaniasis.<ref name=AHFS2016/> Pentamidine can be given by injection into a vein or muscle or by inhalation.<ref name=AHFS2016/>

Common side effects of the injectable form include low blood sugar, pain at the site of injection, nausea, vomiting, low blood pressure, and kidney problems.<ref name=AHFS2016/> Common side effects of the inhaled form include wheezing, cough, and nausea.<ref name=AHFS2016/> It is unclear if doses should be changed in those with kidney or liver problems.<ref name=AHFS2016/> Pentamidine is not recommended in early pregnancy but may be used in later pregnancy.<ref name=AHFS2016/> Its safety during breastfeeding is unclear.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Pentamidine is in the aromatic diamidine family of medications.<ref>Template:Cite book</ref> While the way the medication works is not entirely clear, it is believed to involve decreasing the production of DNA, RNA, and protein.<ref name=AHFS2016/>

Pentamidine came into medical use in 1937.<ref name=Mag2012>Template:Cite book</ref> It is on the World Health Organization's List of Essential Medicines.<ref name="WHO21st">Template:Cite book</ref> It is available as a generic medication.<ref name=AHFS2016>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> In regions of the world where trypanosomiasis is common pentamidine is provided for free by the World Health Organization (WHO).<ref name=WHO2016>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Medical uses

• Treatment of PCP caused by Pneumocystis jirovecii<ref name=":10">{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

• Prevention of PCP in adults with HIV who have one or both of the following:
  • History of PCP
  • CD4+ count ≤ 200mm³<ref name=":11">{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

• Treatment of leishmaniasis<ref name=":1" />
• Treatment of African trypanosomiasis caused by Trypanosoma brucei gambiense<ref name=":1" />
• Balamuthia infections<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

• Pentamidine is classified as an orphan drug by the U.S. Food and Drug Administration<ref>{{#invoke:citation/CS1|citation

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Other uses

• Use as an antitumor drug has also been proposed.<ref name="pmid18056463">Template:Cite journal</ref>
• Pentamidine is also identified as a potential small molecule antagonist that disrupts this interaction between S100P and RAGE receptor.<ref name="pmid25084534">Template:Cite journal</ref>

Special populations

Pregnancy

It has not been shown to cause birth defects in animal studies when given intravenously. There are no controlled studies to show if pentamidine can harm the fetus in pregnant women. It is only recommended if the drug of choice trimethoprim-sulfamethoxazole is contraindicated.<ref name=":12">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Breastfeeding

There is no information regarding the excretion of pentamidine in breast milk, but since the adverse effects on breastfed infants are unknown currently, it is recommended by the manufacturer for the infant to not be breastfed or for the mother to stop the drug. Risks versus benefits for the mother should be considered when making this decision.<ref name=":12" />

Children

Pentamidine can be used in the prevention of PCP in children with HIV who cannot tolerate Trimethoprim/Sulfamethoxazole and can use a nebulizer. Intranvenous solutions of pentamidine should only be used in children with HIV older than 2 years old when other treatments are unavailable<ref name=":8">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Elderly

There is no data for the use of pentamidine in this specific population.<ref name=":12" />

Contraindications

• Patients with a history of anaphylaxis or hypersensitivity to pentamidine isethionate<ref name=":10" />

Side effects

Common

• Burning pain, dryness, or sensation of lump in throat
• Chest pain
• Coughing
• difficulty in breathing
• difficulty in swallowing
• skin rash
• wheezing<ref name=":4">{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

Rare

• Nausea and vomiting
• Pain in upper abdomen, possibly radiating to the back
• Severe pain in side of chest
• Shortness of breath<ref name=":4" />

Others

• Blood: Pentamidine frequently causes leukopenia and less often thrombopenia, which may cause symptomatic bleeding. Some cases of anemia, possibly related to folic acid deficiency, have been described.<ref name=":4" />
• Cardiovascular: Hypotension, which may be severe. Severe or fatal arrhythmias and heart failure are quite frequent.<ref name=":10" />
• Kidney: 25 percent develop signs of nephrotoxicity ranging from mild, asymptomatic azotemia (increased serum creatinine and urea) to irreversible renal failure. Ample fluids or intravenous hydration may prevent some nephrotoxicity.<ref name=":10" />
• Liver: Elevated liver enzymes are associated with intravenous use of pentamidine. Hepatomegaly and hepatitis have been encountered with long term prophylactic use of pentamidine inhalation.<ref name=":10" />
• Neurological: Dizziness, drowsiness, neuralgia, confusion, hallucinations, seizures and other central side effects are reported.<ref name=":10" />
• Pancreas: Hypoglycemia that requires symptomatic treatment is frequently seen. On the other hand, pentamidine may cause or worsen diabetes mellitus.<ref name=":10" />
• Respiratory: Cough and bronchospasm, most frequently seen with inhalation.<ref name=":10" />
• Skin: Severe local reactions after extravasculation of intravenous solutions or following intramuscular injection treatment have been seen. Pentamidine itself may cause rash, or rarely Stevens–Johnson syndrome or Lyell syndrome.<ref name=":10" />
• Eye discomfort, conjunctivitis, throat irritation, splenomegaly, Herxheimer reaction, electrolyte imbalances (e.g. hypocalcemia).<ref name=":10" />

Drug interactions

The additional or sequential use of other nephrotoxic drugs like aminoglycosides, amphotericin B, capreomycin, colistin, polymyxin B, vancomycin, foscarnet, or cisplatin should be closely monitored, or whenever possible completely avoided.<ref name=":10" />

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.<ref name=":10" /><ref name=":6" /> 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 a broken and unreadable mitochondrial genome.<ref name=":6">Template:Cite book</ref>

Resistance

Strains of the Trypanosoma brucei parasite that are resistant to pentamidine have been discovered. Pentamidine is brought into the mitochondria through carrier proteins, and the absence of these carriers prevents the drug from reaching its site of action.<ref name=":6" />

Pharmacokinetics

Absorption

Pentamidine is completely absorbed when given intravenously or intramuscularly. When inhaled through a nebulizer, pentamidine accumulates in the bronchoalveolar fluid of the lungs at a higher concentration compared to injections. The inhaled form is minimally absorbed in the blood, but the effects of chronic inhaled administration on these levels are not known.<ref name=":11" /> Absorption is unreliable when given orally.<ref name=":1" />

Distribution

When injected, pentamidine binds to tissues and proteins in the plasma. It accumulates in the kidney, liver, lungs, pancreas, spleen, and adrenal glands.<ref name=":2" /> Additionally, pentamidine does not reach curative levels in the cerebrospinal fluid.<ref name=":1" /> It has a volume of distribution of 286–1356 liters when given intravenously and 1658–3790 liters when given intramuscularly.<ref name=":7">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Inhaled pentamidine is mainly recovered from the bronchoalveolar lavage fluid of the lungs.<ref name=":11" /><ref name=":2" />

Metabolism

Pentamidine is primarily metabolized by cytochrome P450 enzymes in the liver.<ref name=":7" /><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Up to 12% of pentamidine is eliminated in the urine unchanged.<ref name=":10" />

Elimination

Pentamidine has an average half-life of five to eight hours when given intravenously and seven to eleven hours when given intramuscularly. However, these may increase with severe kidney problems.<ref name=":2">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Pentamidine can remain in the system for as long as eight months after the first injection.<ref name=":6" />

Chemistry

Pentamidine isethionate for injection is commercially available as a lyophilized, 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 intravenous HIV medications like zidovidine and intravenous heart medications like diltiazem. However, intravenous solutions of antiviral foscarnet and antifungal fluconazole are incompatible with pentamidine.<ref name=":10" /> To avoid side-effects associated with intravenous administration, the solution should be slowly infused to minimize the release of histamine.<ref name=":6" />

History

Pentamidine was first used to treat African trypanosomiasis in 1937 and leishmaniasis in 1940 before it was registered as pentamidine mesylate in 1950.

The sudden increase in requests for use of pentamidine isethionate in then unlicensed form from the CDC in the early 1980s for treating Pneumocystis jirovecii in young male patients was key in identifying the emergence of the HIV/AIDS epidemic at that time. <ref>Template:Cite journal</ref>

Its efficacy against Pneumocystis jirovecii was demonstrated in 1987, following its re-emergence on the drug market in 1984 in the current isethionate form.<ref name=":1">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Trade names and dose form

For oral inhalation and for nebulizer use:<ref name=Bank2016>Template:Cite journal</ref>

• NebuPent Nebulizer (APP Pharmaceuticals LLC - US)

For intravenous and intramuscular use:<ref name=Bank2016/>

• 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:<ref name=Bank2016/>
  • Pentamidine isethionate (Abbott)
  • Pentacarinat (Sanofi-Aventis)
  • Pentacrinat (Abbott)
  • Pentam (Abbott)
  • Pneumopent

See also

• Netropsin
• Lexitropsin

External links

• {{#invoke:citation/CS1|citation

|CitationClass=web }}