In WM9, DU145, C4-2, Hey, WM480, and A549 cells, pentamidine administration (0–10 µg/mL; 6 days) reduces cancer cell proliferation in a concentration-dependent manner [1]. It has been established that pentamidine isethionate is cytotoxic to Leishmania infantum promastigotes. Pentamidine isethionate was 60 times more leishmanicidal than cisplatin after 72 hours of incubation. Compared to cisplatin, pentamidine isethionate causes a greater amount of programmed cell death (PCD), which is linked to suppression of DNA synthesis and cell cycle arrest in the G2/M phase. When pentamidine isethionate is bound to calf thymus DNA (CT-DNA), the DNA double helix undergoes structural changes that align with the B-to-A transition. The protein's β-sheet composition increases by 6% as a result of the interaction between pentamidine isethionate and ubiquitin [2].

The treatment of athymic nude mice with pentamidine (0.25 mg/mouse; intramuscular injection; every 2 days; for 4 weeks) can effectively limit the growth of WM9 human melanoma [1].

Cell Viability Assay[1]
Cell Types: WM9, DU145, C4-2, Hey, WM480 and A549 Cell
Tested Concentrations: 0-10 µg/mL
Incubation Duration: 6 days
Experimental Results: Growth of all six cell lines in culture Inhibited in a concentration-dependent manner, with complete growth inhibition of the cell line at 10 µg/mL.

Animal/Disease Models: Athymic nude mice (6 weeks old) injected with WM9 cells [1]
Doses: 0.25mg/mouse
Route of Administration: intramuscularinjection; once every 2 days; for 4 consecutive weeks
Experimental Results: Dramatically inhibited WM9 human melanoma Growth in nude mice.

Absorption, Distribution and Excretion
This product is poorly absorbed from the gastrointestinal tract and is usually administered parenterally. Although sterile abscesses may form after use, pentanemidine isothiocyanate is well absorbed from the parenteral administration site. Following a single intravenous injection, the drug disappears from the plasma with an apparent half-life of several minutes to several hours; this is followed by a slower distribution phase and a longer elimination phase lasting several weeks to months. Pharmacokinetic parameters in patients with African trypanosomiasis vary significantly among individuals. The mean systemic plasma clearance after a single dose is approximately 1120 mL/min, but the volume of distribution is approximately 25,000 L, which explains the prolonged mean elimination half-life of approximately 12 days… Renal clearance of pentamidine is only 2% to 11% of its systemic clearance on average… However, whether the drug is metabolized or excreted in the bile… is unclear. In patients receiving multiple injections of this drug over 13 days to treat Pneumocystis pneumonia, drug accumulation occurs, preventing the attainment of steady-state plasma concentrations… /Pentamidine isothiocyanate/
…After multiple parenteral administrations, the highest drug concentrations were found in the liver, kidneys, adrenal glands, and spleen of HIV-positive patients, while only trace amounts were detected in brain tissue…In these patients, moderate but therapeutic pulmonary drug concentrations were achieved after five daily doses of 4 mg/kg base. Inhaled pentamidine aerosols achieve higher pulmonary drug concentrations for the prevention or adjunctive treatment of mild to moderate Pneumocystis pneumonia; this route of administration results in less systemic absorption and lower toxicity compared to intravenous administration, and is suitable for both adults and children. The actual dose reaching the lungs depends on the particle size produced by the nebulizer and the patient's breathing pattern. /Pentamidine isothiocyanate/
Nebulized pentamidine achieves pulmonary concentrations approximately 10 to 100 times higher than the equivalent dose of intravenously administered pentamidine.
Systemic absorption of inhaled pentamidine is minimal. In most cases, serum pentamidine concentrations are below 20 ng/mL after a nebulized dose of 4 mg/kg (compared to 612 ng/mL after a single intravenous injection of 4 mg/kg). Peak systemic absorption occurs at or near the end of inhalation therapy.
For more complete data on the absorption, distribution, and excretion of pentamidine (14 types), please visit the HSDB record page.
Metabolism/Metabolites
Hepatic metabolism.
The in vitro conversion of pentamidine to its corresponding amidoximes (N-hydroxypenttamidine and N,N'-dihydroxypenttamidine) in the supernatant of rat liver homogenate centrifuged at 9000 xg was investigated using high-performance liquid chromatography (HPLC). The presence of two amidoxime peaks in the chromatograms was confirmed by secondary ion mass spectrometry and definitive synthesis of the suspected metabolites. The metabolic reactions were catalyzed by the cytochrome P-450 system (a mixed-function oxidase). The rate constant (Km) for the monohydroxylated product was 0.48 mM, with a maximum reaction rate (Vmax) of 29.50 pmol/min/mg protein; while the Km for the dihydroxylated metabolite was 0.73 mM, with a maximum reaction rate (Vmax) of 4.10 pmol/min/mg protein. …
Recent studies have shown that the antiprotozoal/antifungal drug pentamidine [1,5-bis(4-amidinylphenoxy)pentane] can be metabolized in rat liver fractions by high-performance liquid chromatography to at least six putative metabolites. …This study identified two major microsomal metabolites as 2-pentanol and 3-pentanol analogs of pentamidine [1,5-bis(4-amidinylphenoxy)-2-pentanol; and 1,5-bis(4-amidinylphenoxy)-3-pentanol]. In addition, a seventh putative metabolite, p-hydroxybenzoic acid, a fragment of the original drug, was discovered and identified. ... Cytochrome P-450 has been confirmed as the enzyme system responsible for pentamidine metabolism... Mixed-function oxidases can rapidly convert pentamidine to hydroxylated metabolites, but it is unclear which cytochrome P-450 isoenzymes are responsible for this process.
The antibiogenic animal drug pentamidine [1,5-bis(4'-amidinylphenoxy)pentane] has previously been shown to be metabolized in rat liver microsomes, and five of the seven putative primary metabolites have been identified. With the synthesis and identification of the two remaining metabolites, 5-(4'-amidinylphenoxy)valerate and 5-(4'-amidinylphenoxy)-1-pentanol, the primary metabolism of pentamidine in rats appears to be well elucidated. ... Secondary metabolites were identified using ex vivo perfused rat livers and [14C] pentamidine. High-performance liquid chromatography (HPLC) analysis of perfused liver samples revealed only two novel radioactive peaks. These peaks decreased or disappeared upon treatment of the liver samples with sulfatase or β-glucuronidase, and peaks identified as p-hydroxybenzoic acid and 5-(4'-amidinylphenoxy)valerate were generated. It was concluded that only these two primary metabolites were bound to sulfate or glucuronic acid. Pentamidine is a substrate of the human liver microsomal P450 enzyme CYP2C19. (From table) Liver. Half-life: 9.1–13.2 hours

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Biological half-life
9.1–13.2 hours
Intramuscular injection: 9.1 to 13.2 hours. Intravenous injection: Approximately 6.5 hours. Terminal half-life: 2 to 4 weeks. Renal impairment: The half-life of pentamidine may be prolonged in patients with renal insufficiency; however, no correlation has been found between renal function and pentamidine plasma clearance.

Toxicity Summary
The mechanism of action of pentamidine is not fully understood. It is currently believed that the drug interferes with nuclear metabolism, thereby inhibiting the synthesis of DNA, RNA, phospholipids, and proteins. Hepatotoxicity
In patients with Pneumocystis carinii pneumonia treated with pentamidine for 2 to 3 weeks, 9% to 15% experienced elevated serum transaminases. Significant liver injury has also been reported clinically following this treatment, but it is always accompanied by various other serious complications such as respiratory failure, renal failure, and pancreatitis. Liver injury usually occurs within days of starting treatment and is characterized by acute liver necrosis, significantly elevated serum transaminase levels, rapidly prolonged prothrombin time, and mild or no jaundice. Recovery is usually rapid and generally complete. Probability Score: D (Possibly a rare cause of clinically significant liver injury).

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Protein binding rate
69%

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Drug interactions
Because nephrotoxicity may be additive, close monitoring or avoidance of concurrent or sequential use of pentamidine isothiocyanate and other drugs with similar toxic potential, such as aminoglycosides, amphotericin B, capreomycin, colistin, cisplatin, sodium phosphonoformate, methoxyflurane, polymyxin B, or vancomycin, is necessary.
Concomitant use of pentamidine with other nephrotoxic drugs may increase the risk of nephrotoxicity; renal function testing, dose reduction, and/or adjustment of dosing intervals may be necessary.
Renal side effects are frequently observed after parenteral administration of pentamidine. This study used a rat model to assess nephrotoxicity by measuring urinary tubular cell loss, malate dehydrogenase activity, and creatinine clearance. Furthermore, we investigated the effects of other nephrotoxic drugs (such as tobramycin, amphotericin B, and cyclosporine) on pentamidine-related nephrotoxicity and demonstrated the potential to reduce this toxicity through combination therapy with other drugs. Renal tubular toxicity of pentamidine (1, 10, or 20 mg/kg daily) is dose-dependent and reversible. Co-administration of fosfomycin (1 x 500 or 2 x 250 mg/kg daily) and D-glucuronide-1,5-lactam (2 x 5 mg/kg daily) reduces toxicity, while co-administration of tobramycin (2 x 2.5 mg/kg daily), amphotericin B (1 mg/kg daily), and cyclosporine (10 mg/kg daily) enhances toxicity. Furthermore, in rats treated with pentamidine, verapamil (1.5 mg/kg twice daily) and enalapril (5 mg/kg daily) both increased creatinine clearance. Concomitant use of sodium phosphonoformate and pentamidine may lead to severe, but reversible hypocalcemia, hypomagnesemia, and nephrotoxicity. For more complete data on pentamidine interactions (8 items in total), please visit the HSDB records page.

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Non-human toxicity values
Subcutaneous LD50 in mice: 120 mg/kg
Intraperitoneal LD50 in mice: 63 mg/kg
Intravenous LD50 in mice: 15 mg/kg

[1]. Pentamidine is an inhibitor of PRL phosphatases with anticancer activity. Mol Cancer Ther. 2002 Dec;1(14):1255-64.

[2]. Pentamidine is an antiparasitic and apoptotic drug that selectively modifies ubiquitin. Chem Biodivers, 2005. 2(10): p. 1387-400.

[3]. Pentamidine: a review. Rev Infect Dis. 1985 Sep-Oct;7(5):625-34.

[4]. Pentamidine: a drug to consider re-purposing in the targeted treatment of multi-drug resistant bacterial infections? J Lab Precis Med 2017;2:49.

Therapeutic Uses
Pentamidine is indicated for the treatment of Pneumocystis carinii pneumonia (PCP) in immunocompromised patients, including those with acquired immunodeficiency syndrome (AIDS). For patients who can tolerate sulfamethoxazole and trimethoprim, sulfamethoxazole is considered a first-line treatment for PCP. /Included on US product label/ Pentamidine can be used as adjunctive therapy for visceral leishmaniasis (leishmaniasis) caused by Leishmania donovani. Sodium antimony gluconate, a pentavalent antimony derivative, is considered a first-line treatment for visceral leishmaniasis. /Not included on US product label/ Pentamidine is used as adjunctive therapy for cutaneous leishmaniasis caused by Leishmania tropicalis, Leishmania macrophylla, Leishmania mexicanis, Leishmania esculenta, Leishmania peruviana, Leishmania guinea, and Leishmania brasiliensis. Sodium antimony gluconate, a pentavalent antimony derivative, is considered the first-line treatment for cutaneous leishmaniasis. /Not included in the US product label/
Pentamidine spray is indicated for secondary prevention of Pneumocystis carinii pneumonia (in patients with at least one previous episode of Pneumocystis carinii pneumonia) and primary prevention (in HIV-infected patients with a CD4 lymphocyte count ≤200/mm³). /Included in the US product label/
For more complete data on the therapeutic uses of pentamidine (12 types), please visit the HSDB record page.

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Drug Warning
Deaths due to severe hypotension, hypoglycemia, acute pancreatitis, and arrhythmias have been reported in patients receiving pentamidine isothiocyanate, whether intramuscular or intravenous. Severe hypotension may occur after a single intramuscular or intravenous injection, with a greater likelihood of occurrence with rapid intravenous injection. Therefore, this drug should only be used in patients diagnosed with Pneumocystis carinii pneumonia. Patients should be closely monitored for serious adverse reactions.
It has been reported that at least 25% of patients with Pneumocystis carinii pneumonia treated with parenteral pentamidine isothiocyanate experience nephrotoxicity. Pentamidine-induced nephrotoxicity manifests as elevated serum creatinine and/or blood urea nitrogen (BUN), typically developing slowly and appearing in the second week of treatment. Azotemia has also been reported. Renal impairment is usually mild to moderate and reversible upon discontinuation of pentamidine; however, acute renal failure (e.g., serum creatinine concentration greater than 6 mg/dL) or severe renal impairment requiring discontinuation of the drug are occasionally observed. Limited evidence suggests that AIDS patients may experience a higher frequency of nephrotoxicity and hyperkalemia compared to other patients receiving parenteral pentamidine treatment; some patients may experience more severe hyperkalemia. Rarely, acute renal failure caused by pentamidine may be accompanied by myoglobinuria or gross hematuria. Dehydration or concomitant use of other nephrotoxic drugs may increase the risk and severity of pentamidine-induced kidney damage. At least one patient receiving pentamidine inhalation has reported acute renal failure; occasional reports have been made of back pain and nephritis in patients receiving nebulized pentamidine. Cardiopulmonary arrest (after rapid intravenous injection), ventricular tachycardia, atypical ventricular tachycardia (torsades de pointes), ECG abnormalities, and facial flushing have also been reported in patients receiving pentamidine via parenteral administration. The risk of hypotension following intramuscular or intravenous injection of pentamidine isothiocyanate has not been directly compared, but some data suggest that there is no difference in the frequency of hypotension between the two routes of administration when the drug is infused intravenously for at least 60 minutes. Hypotension may be particularly likely following rapid intravenous injection or infusion. To minimize the risk of this adverse reaction with intravenous pentamidine isothiocyanate, the infusion time should be controlled between 60 and 120 minutes. However, there are reports of some patients experiencing hypotension that cannot be relieved even after adjusting the infusion rate, and that hypotension persists until the end of the infusion and requires volume resuscitation to correct. Hypotension, hypertension, tachycardia, palpitations, syncope, dizziness, lightheadedness, hyperhidrosis, cerebrovascular accident, vasodilation, and vasculitis have been reported occasionally in patients receiving oral inhaled pentamidine.
Since pentamidine has become available, there has been renewed interest in its use as a primary treatment for Pneumocystis carinii pneumonia in HIV-positive patients. /Authors/ A retrospective analysis of 24 patients with Pneumocystis carinii pneumonia treated with pentamidine was conducted to understand the incidence and severity of adverse reactions. 20 of the 24 patients (83%) experienced some adverse reaction. The most common adverse reactions included abnormal liver function (58%), nausea and vomiting (46%), hypoglycemia (33%), azotemia (25%), and injection site pain (25%).
For more complete data on drug warnings for pentamidine (25 of them), please visit the HSDB record page.

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Pharmacodynamics
Pentamidine is an antibiopharmaceutical drug. It is an aromatic diamidine compound known to be active against Pneumocystis carinii. The exact mechanism of its antiprotozoan action is unclear. In vitro studies have shown that this drug has inhibitory effects on mammalian tissues and protozoan trypanosomes (Crithidia oncopelti), interfering with nuclear metabolism and thereby inhibiting the synthesis of DNA, RNA, phospholipids, and proteins. Little is known about the pharmacokinetics of this drug. It can also be used to treat leishmaniasis and prevent sleeping sickness caused by Trypanosoma brucei gambiense. Pre-treatment hydration can reduce the incidence and severity of side effects, including hepatic and renal dysfunction, hypertension, hypotension, hypoglycemia, hypocalcemia, leukopenia, thrombocytopenia, anemia, and allergic reactions. The drug is generally well tolerated.

C19H24N4O2

340.41946

340.189

100-33-4

Pentamidine isethionate;140-64-7;Pentamidine dihydrochloride;50357-45-4;Pentamidine dimesylate;6823-79-6

4735

White to off-white solid powder

1.2±0.1 g/cm3

539.4±60.0 °C at 760 mmHg

186ºC (dec.)

280.0±32.9 °C

0.0±1.4 mmHg at 25°C

1.593

2.47

4

4

10

25

376

0

XDRYMKDFEDOLFX-UHFFFAOYSA-N

InChI=1S/C19H24N4O2/c20-18(21)14-4-8-16(9-5-14)24-12-2-1-3-13-25-17-10-6-15(7-11-17)19(22)23/h4-11H,1-3,12-13H2,(H3,20,21)(H3,22,23)

4-[5-(4-carbamimidoylphenoxy)pentoxy]benzenecarboximidamide

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)