Abacavir

Absorption

Rapid and extensive after oral administration (83% bioavailability, tablet). When a 300 mg tablet is given twice daily to subjects, the peak plasma concentration (Cmax) was 3.0 ± 0.89 mcg/mL and the area under the curve (AUC 0-12 hours) was 6.02 ± 1.73 mcg?hr/mL.

Toxicity

Some myocardial degeneration has been noticed in rats and mice. The most commonly reported adverse reactions of at least moderate intensity (incidence ≥10%) in adult HIV-1 clinical trials were nausea, headache, malaise and fatigue, nausea and vomiting, and dreams/sleep disorders. Serious hypersensitivity reactions have been associated with abacavir which has been strongly linked to the presence of the HLA-B*57:01 allele. This reaction manifests itself in patients within the first 6 weeks of treatment. Patients should be tested for the presence of this allele as recommended by the U.S Food and Drug Administration (FDA).

Description

The drug is extensively metabolized via stepwise phosphorylation to 5′-mono-, di-, and triphosphate. Abacavir is well absorbed (>75%) and penetrates the CNS. The drug can be taken without regard to meals. The drug does not show any clinically significant drug–drug interactions. Abacavir has been reported to produce life-threatening hypersensitivity reactions. The major use of abacavir appears to be in combination with other nucleoside RT inhibitors. A fixed-combination product has recently been approved by the U.S. FDA consisting of 300 mg of ABC, 150 mg of 3TC, and 300 mg of ZDV (Trizivar). The combination has been shown to be superior to other combinations in reducing viral load as well as to show improvement in CD4 cell count.

Description

Abacavir, is an antiretroviral drug. When a virus (such as HIV) tries to manufacture DNA from the viral RNA, it unknowingly incorporates abacavir instead of a natural component of DNA, guanosine, which stops the virus from reproducing. Suggested by Mamoun Abacavir.

Originator

Ziagen ,GlaxoSmithKline

The Uses of Abacavir

Abacavir is a commonly used nucleoside analogue with potent antiviral activity against HIV-1. - See more at: http://www.selleckchem.com/products/abacavir-sulfate.html#sthash.lApvcTNO.dpuf

The Uses of Abacavir

A nucleoside reverse transcriptase inhibitor (NRTI).

Background

Abacavir (ABC) is a powerful nucleoside analog reverse transcriptase inhibitor (NRTI) used to treat HIV and AIDS. Chemically, it is a synthetic carbocyclic nucleoside and is the enantiomer with 1S, 4R absolute configuration on the cyclopentene ring. In vivo, abacavir sulfate dissociates to its free base, abacavir.

What are the applications of Application

Ziagen is a carbocyclic nucleoside analogue with inhibitory activity against HIV-1

Indications

Abacavir is indicated in combination with other anti-retroviral agents for the treatment of HIV-1 infection. It is available in a combination product alongside dolutegravir and lamivudine for the treatment of adult and pediatric patients with HIV-1 who weigh ≥10 kg.

Indications

Abacavir (Ziagen) is a guanosine nucleoside analogue indicated for the therapy of HIV-1 infection in adults and children. It is used as part of a multidrug regimen and is available in a fixed-dose combination with zidovudine and lamivudine (Trizivir). It is also used for postexposure HIV infection prophylaxis.

Definition

ChEBI: Abacavir is a 2,6-diaminopurine that is (1S)-cyclopent-2-en-1-ylmethanol in which the pro-R hydrogen at the 4-position is substituted by a 2-amino-6-(cyclopropylamino)-9H-purin-9-yl group. A nucleoside analogue reverse transcriptase inhibitor (NRTI) with antiretroviral activity against HIV, it is used (particularly as the sulfate) with other antiretrovirals in combination therapy of HIV infection. It has a role as a HIV-1 reverse transcriptase inhibitor, an antiviral drug and a drug allergen.

Manufacturing Process

Treatment of 2,5-diamino-4,6-dihydroxypyrimidine (I) with (chloromethylene)dimethylammonium chloride yielded the dichloropyrimidine with both amino groups derivatized as amidines. Partial hydrolysis with aqueous HCl in hot ethanol gave N-(2-amino-4,6-dichloro-pyrimidin-5-yl)-N,Ndimethylformamidene (II). Subseqent buffered hydrolysis at pH 3.2 yielded the (2-amino-4,6-dichloro-pyrimididin-5-ylamino)acetaldehyde (III). Condensation chloropyrimidine (III) with (1S,4R)-4-amino-2-cyclopentene-1- methanol (IV) in the presence of triethylamine and NaOH gave [2-amino-4- chloro-6-(4-hydroxymethyl-cyclopent-2-enylamino)pyrimidin-5-ylamino]- acetaldehyde (V). The correct enantiomer (IV) of racemic aminocyclopentene was obtained by resolution of diastereomeric salts with D-dibenzoyltartaric acid. Cyclization of (V) to the corresponding purine was accomplished with refluxing triethyl orthoformate or diethoxymethyl acetate to give nucleoside analogue [4-(2-amino-6-chloro-purin-9-yl)-cyclopent-2-enyl]methanol (VI). Displacement of chloride in the purine nucleus with cyclopropyl amine in refluxing butanol afforded abacavir. The structure of obtained compound was confirmed by 1H NMR method and elemental analysis.
In practice it is usually used as sulfate salt.

Therapeutic Function

Antiviral

Antimicrobial activity

Abacavir has activity against HIV-1, HIV-2 and human T-cell lymphotrophic virus type-1 (HTLV-1).

Acquired resistance

Resistance is associated with specific changes in codons 184 with 65, 74 or 115 in the HIV reverse transcriptase codon region.

General Description

Abacavir is a nucleoside reverse transcriptase inhibitorNRTI that has been approved for use in combination therapiesfor the treatment of HIV and AIDS. Once in the tissues,it is metabolized by stepwise phosphorylation to themonophosphate, diphosphate, and triphosphate. Abacavir ishighly bioavailable (＞75%) and is effective by the oralroute. It penetrates the blood-brain barrier efficiently.Abacavir has been reported to produce life-threatening hypersensitivityreactions in some patients.

Pharmaceutical Applications

A synthetic analog of guanine formulated for oral use.

Pharmacokinetics

Abacavir is a nucleoside reverse transcriptase inhibitor (NRTI) with activity against Human Immunodeficiency Virus Type 1 (HIV-1). Abacavir is phosphorylated to active metabolites that compete for incorporation into viral DNA. They inhibit the HIV reverse transcriptase enzyme competitively and act as a chain terminator of DNA synthesis. The concentration of drug necessary to effect viral replication by 50 percent (EC50) ranged from 3.7 to 5.8 μM (1 μM = 0.28 mcg/mL) and 0.07 to 1.0 μM against HIV-1IIIB and HIV-1BaL, respectively, and was 0.26 ± 0.18 μM against 8 clinical isolates. Abacavir had synergistic activity in cell culture in combination with the nucleoside reverse transcriptase inhibitor (NRTI) zidovudine, the non-nucleoside reverse transcriptase inhibitor (NNRTI) nevirapine, and the protease inhibitor (PI) amprenavir; and additive activity in combination with the NRTIs didanosine, emtricitabine, lamivudine, stavudine, tenofovir, and zalcitabine.

Pharmacokinetics

Oral absorption: 83%
C_max 300 mg oral, twice daily: 3.0 ± 0.89 mg/L
600 mg once daily: 4.26 mg/L
Plasma half-life: 1.5 h
Volume of distribution: 0.8 L/kg
Plasma protein binding: c. 49%
Absorption
After oral administration abacavir sulfate undergoes rapid and extensive absorption unaffected by food.
Distribution
It penetrates well into the cerebrospinal fluid (CSF) and is an NRTI of choice if this characteristic is thought desirable. Good penetration into the male genital tract has been observed. The drug is secreted into human breast milk.
Metabolism
It is primarily metabolized in the liver, mainly by alcohol dehydrogenase and glucuronidation.
Excretion
Around 83% of the dose is eliminated in the urine, <2% as unchanged drug; the remainder is excreted in the feces. Dose adjustment is unnecessary in renal impairment. It can be used in moderate hepatic impairment, but is contraindicated if dysfunction is severe.

Clinical Use

Treatment of HIV infection in adults and children (in combination with other antiretroviral drugs)

Side Effects

Life-threatening hypersensitivity reactions occur in 5–8% of all individuals, necessitating discontinuation of the drug. Typically patients present within the first 6 weeks of starting treatment with fever, rash or other symptoms that worsen in severity with continued drug exposure. Hypersensitivity is associated with carriage of the major histocompatibility complex class I allele HLA-B57*01 and screening for this allele can significantly reduce the incidence of this effect.
Current or recent (within the preceding 6 months) use of abacavir has been associated with a risk of myocardial infarction, but studies have yielded conflicting data.

Side Effects

Abacavir is associated with side effects such as anorexia, nausea, vomiting, malaise, headache, and insomnia. A potentially fatal hypersensitivity reaction develops in approximately 5% of patients, usually early in the course of treatment. Fever and rash are the most common symptoms of this reaction; malaise, respiratory symptoms, and gastrointestinal complaints may also occur. Resistance to abacavir may be associated with resistance to zidovudine, didanosine, and lamivudine.

Drug interactions

Potentially hazardous interactions with other drugs
Antivirals: possibly reduces effects of ribavirin; concentration reduced by tipranavir.
Orlistat: absorption possibly reduced by orlistat.

Metabolism

Hepatic, by alcohol dehydrogenase and glucuronosyltransferase to a 5′-carboxylic acid metabolite and 5′-glucuronide metabolite, respectively. These metabolites have no antiviral activity. Abacavir is not significantly metabolized by cytochrome P450 enzymes.

Metabolism

Abacavir is primarily metabolised by the liver with approximately 2% of the administered dose being renally excreted, as unchanged compound. The primary pathways of metabolism in man are by alcohol dehydrogenase and by glucuronidation to produce the 5'-carboxylic acid and 5'-glucuronide which account for about 66% of the administered dose. The metabolites are excreted in the urine.