Abacavir - Revision history

Danbot: Reduce excessive bold: 24 -> 10 instances

2026-03-22T08:46:14Z

Reduce excessive bold: 24 -> 10 instances

← Older revision		Revision as of 08:46, 22 March 2026
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	*600 mg PO daily, given as either 300 mg twice daily or 600 mg once daily<ref name="ZiagenPI"/>		*600 mg PO daily, given as either 300 mg twice daily or 600 mg once daily<ref name="ZiagenPI"/>
	*May take with or without food		*May take with or without food
	~~'''~~Must screen for HLA-B5701 before initiating~~'''~~ (see Contraindications/Comments)<ref name="ZiagenPI"/>		Must screen for HLA-B5701 before initiating (see Contraindications/Comments)<ref name="ZiagenPI"/>

	==Pediatric Dosing==		==Pediatric Dosing==
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	===Hepatic Dosing===		===Hepatic Dosing===
	*Adult:<ref name="ZiagenPI"/>		*Adult:<ref name="ZiagenPI"/>
	**Mild impairment (Child-Pugh A): ~~'''~~200 mg PO twice daily~~'''~~ (reduced dose; use oral solution to enable this)		**Mild impairment (Child-Pugh A): 200 mg PO twice daily (reduced dose; use oral solution to enable this)
	**Moderate or severe impairment (Child-Pugh B or C): '''Contraindicated'''		**Moderate or severe impairment (Child-Pugh B or C): '''Contraindicated'''
	*Pediatric: Not studied		*Pediatric: Not studied
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	==Contraindications==		==Contraindications==
	*Allergy to class/drug		*Allergy to class/drug
	~~'''~~HLA-B5701-positive~~'''~~ patients<ref name="ZiagenPI"/>		HLA-B5701-positive patients<ref name="ZiagenPI"/>
	*Prior hypersensitivity reaction to abacavir ('''NEVER rechallenge''')<ref name="ZiagenPI"/>		*Prior hypersensitivity reaction to abacavir ('''NEVER rechallenge''')<ref name="ZiagenPI"/>
	*Moderate or severe hepatic impairment (Child-Pugh B or C)<ref name="ZiagenPI"/>		*Moderate or severe hepatic impairment (Child-Pugh B or C)<ref name="ZiagenPI"/>
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	===Serious===		===Serious===
	'''Hypersensitivity reaction (Boxed Warning):''' Multi-organ syndrome occurring in ~8% without HLA screening (~1% with screening). Median onset 9 days (range: within first 6 weeks, though can occur any time). Presents with ≥2 of the following symptom groups:<ref name="ZiagenPI"/><ref name="HLA">Abacavir Therapy and HLA-B57:01 Genotype. ''Medical Genetics Summaries''. NCBI Bookshelf. Updated 2025.</ref>		'''Hypersensitivity reaction (Boxed Warning):''' Multi-organ syndrome occurring in ~8% without HLA screening (~1% with screening). Median onset 9 days (range: within first 6 weeks, though can occur any time). Presents with ≥2 of the following symptom groups:<ref name="ZiagenPI"/><ref name="HLA">Abacavir Therapy and HLA-B57:01 Genotype. ''Medical Genetics Summaries''. NCBI Bookshelf. Updated 2025.</ref>
	**~~'''~~Group 1:~~'''~~ Fever		**Group 1: Fever
	**~~'''~~Group 2:~~'''~~ Rash (maculopapular or urticarial)		**Group 2: Rash (maculopapular or urticarial)
	**~~'''~~Group 3:~~'''~~ GI (nausea, vomiting, diarrhea, abdominal pain)		**Group 3: GI (nausea, vomiting, diarrhea, abdominal pain)
	**~~'''~~Group 4:~~'''~~ Constitutional (malaise, fatigue, body aches)		**Group 4: Constitutional (malaise, fatigue, body aches)
	**~~'''~~Group 5:~~'''~~ Respiratory (dyspnea, cough, pharyngitis)		**Group 5: Respiratory (dyspnea, cough, pharyngitis)
	**Symptoms ~~'''~~worsen with each subsequent dose~~'''~~ and resolve within 72 hours of stopping		**Symptoms worsen with each subsequent dose and resolve within 72 hours of stopping
	**'''Rechallenge after hypersensitivity can cause fatal hypotension, multi-organ failure, and death within hours'''<ref name="ZiagenPI"/>		**'''Rechallenge after hypersensitivity can cause fatal hypotension, multi-organ failure, and death within hours'''<ref name="ZiagenPI"/>
	*'''Lactic acidosis with hepatic steatosis''' (NRTI class effect; including fatal cases)<ref name="ZiagenPI"/>		*'''Lactic acidosis with hepatic steatosis''' (NRTI class effect; including fatal cases)<ref name="ZiagenPI"/>
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	==Comments==		==Comments==
	~~'''~~HLA-B5701 screening is mandatory before starting any abacavir-containing product~~'''~~ — this includes Triumeq, Epzicom, and Trizivir. ~6% of Caucasians and ~2–3% of African Americans carry this allele<ref name="HLA"/>		HLA-B5701 screening is mandatory before starting any abacavir-containing product — this includes Triumeq, Epzicom, and Trizivir. ~6% of Caucasians and ~2–3% of African Americans carry this allele<ref name="HLA"/>
	*'''Hypersensitivity recognition:''' A patient on abacavir presenting with a multi-system illness (fever + rash + GI + respiratory symptoms) should be treated as a suspected abacavir hypersensitivity reaction until proven otherwise. '''Discontinue abacavir immediately''' — do not wait for confirmatory testing. Symptoms classically worsen with each dose and improve within 72 hours of stopping<ref name="ZiagenPI"/>		*'''Hypersensitivity recognition:''' A patient on abacavir presenting with a multi-system illness (fever + rash + GI + respiratory symptoms) should be treated as a suspected abacavir hypersensitivity reaction until proven otherwise. '''Discontinue abacavir immediately''' — do not wait for confirmatory testing. Symptoms classically worsen with each dose and improve within 72 hours of stopping<ref name="ZiagenPI"/>
	'''NEVER rechallenge:''' Restarting abacavir after a hypersensitivity reaction — even after resolution — can cause '''fatal anaphylaxis within hours''' (hypotension, renal failure, death). This applies regardless of HLA-B5701 status<ref name="ZiagenPI"/>		'''NEVER rechallenge:''' Restarting abacavir after a hypersensitivity reaction — even after resolution — can cause '''fatal anaphylaxis within hours''' (hypotension, renal failure, death). This applies regardless of HLA-B5701 status<ref name="ZiagenPI"/>
	*~~'''~~Mimics of other diagnoses:~~'''~~ Abacavir hypersensitivity can be misdiagnosed as pneumonia, flu, gastroenteritis, or drug reaction to other agents. If in doubt, stop abacavir and consult [[HIV - AIDS (main)\|HIV/ID]]		*Mimics of other diagnoses: Abacavir hypersensitivity can be misdiagnosed as pneumonia, flu, gastroenteritis, or drug reaction to other agents. If in doubt, stop abacavir and consult [[HIV - AIDS (main)\|HIV/ID]]
	*~~'''~~Ethanol interaction:~~'''~~ Alcohol decreases elimination of abacavir (competition for alcohol dehydrogenase) — increases abacavir exposure by ~41%. No dose adjustment recommended, but be aware in heavy drinkers<ref name="ZiagenPI"/>		*Ethanol interaction: Alcohol decreases elimination of abacavir (competition for alcohol dehydrogenase) — increases abacavir exposure by ~41%. No dose adjustment recommended, but be aware in heavy drinkers<ref name="ZiagenPI"/>
	*~~'''~~Low drug interaction profile:~~'''~~ Abacavir is not metabolized by CYP450 and does not significantly affect other drug levels — one of the safest NRTIs from an interaction standpoint when prescribing in the ED		*Low drug interaction profile: Abacavir is not metabolized by CYP450 and does not significantly affect other drug levels — one of the safest NRTIs from an interaction standpoint when prescribing in the ED
	*~~'''~~Cardiovascular risk:~~'''~~ Some observational data suggested increased MI risk with abacavir use; this remains controversial and has not been confirmed in randomized trials. The FDA has not added a cardiovascular warning<ref name="ZiagenPI"/>		*Cardiovascular risk: Some observational data suggested increased MI risk with abacavir use; this remains controversial and has not been confirmed in randomized trials. The FDA has not added a cardiovascular warning<ref name="ZiagenPI"/>
	*Overdose: No specific antidote; supportive care. Not known if removed by dialysis<ref name="ZiagenPI"/>		*Overdose: No specific antidote; supportive care. Not known if removed by dialysis<ref name="ZiagenPI"/>

Ostermayer: /* Comments */

2026-03-10T23:19:27Z

Comments

← Older revision		Revision as of 23:19, 10 March 2026
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	==Comments==		==Comments==
	'''HLA-B5701 screening is mandatory before starting any abacavir-containing product''' — this includes Triumeq, Epzicom, and Trizivir. ~6% of Caucasians and ~2–3% of African Americans carry this allele<ref name="HLA"/>		'''HLA-B5701 screening is mandatory before starting any abacavir-containing product''' — this includes Triumeq, Epzicom, and Trizivir. ~6% of Caucasians and ~2–3% of African Americans carry this allele<ref name="HLA"/>
	*'''~~ED hypersensitivity~~ recognition:''' A patient on abacavir presenting with a multi-system illness (fever + rash + GI + respiratory symptoms) should be treated as a suspected abacavir hypersensitivity reaction until proven otherwise. '''Discontinue abacavir immediately''' — do not wait for confirmatory testing. Symptoms classically worsen with each dose and improve within 72 hours of stopping<ref name="ZiagenPI"/>		*'''Hypersensitivity recognition:''' A patient on abacavir presenting with a multi-system illness (fever + rash + GI + respiratory symptoms) should be treated as a suspected abacavir hypersensitivity reaction until proven otherwise. '''Discontinue abacavir immediately''' — do not wait for confirmatory testing. Symptoms classically worsen with each dose and improve within 72 hours of stopping<ref name="ZiagenPI"/>
	'''NEVER rechallenge:''' Restarting abacavir after a hypersensitivity reaction — even after resolution — can cause '''fatal anaphylaxis within hours''' (hypotension, renal failure, death). This applies regardless of HLA-B5701 status<ref name="ZiagenPI"/>		'''NEVER rechallenge:''' Restarting abacavir after a hypersensitivity reaction — even after resolution — can cause '''fatal anaphylaxis within hours''' (hypotension, renal failure, death). This applies regardless of HLA-B5701 status<ref name="ZiagenPI"/>
	*'''Mimics of other diagnoses:''' Abacavir hypersensitivity can be misdiagnosed as pneumonia, flu, gastroenteritis, or drug reaction to other agents. If in doubt, stop abacavir and consult [[HIV - AIDS (main)\|HIV/ID]]		*'''Mimics of other diagnoses:''' Abacavir hypersensitivity can be misdiagnosed as pneumonia, flu, gastroenteritis, or drug reaction to other agents. If in doubt, stop abacavir and consult [[HIV - AIDS (main)\|HIV/ID]]

Ostermayer: Created page with "Abacavir is a nucleoside reverse transcriptase inhibitor (NRTI) used in combination with other antiretrovirals for HIV-1 treatment. It is a component of the widely prescribed fixed-dose combination Triumeq (Dolutegravir/abacavir/lamivudine). Abacavir is most notable for its potentially '''fatal hypersensitivity reaction''' linked to the HLA-B5701 allele — one of the best-established pharmacogenomic associations in medicine.
2026-03-10T23:19:05Z

Created page with "Abacavir is a nucleoside reverse transcriptase inhibitor (NRTI) used in combination with other antiretrovirals for HIV-1 treatment. It is a component of the widely prescribed fixed-dose combination Triumeq (Dolutegravir/abacavir/lamivudine). Abacavir is most notable for its potentially '''fatal hypersensitivity reaction''' linked to the HLA-B5701 allele — one of the best-established pharmacogenomic associations in medicine.<ref name="ZiagenPI..."

New page
Abacavir is a nucleoside reverse transcriptase inhibitor (NRTI) used in combination with other antiretrovirals for [[HIV - AIDS (main)|HIV-1]] treatment. It is a component of the widely prescribed fixed-dose combination Triumeq ([[Dolutegravir]]/abacavir/lamivudine). Abacavir is most notable for its potentially '''fatal hypersensitivity reaction''' linked to the HLA-B5701 allele — one of the best-established pharmacogenomic associations in medicine.<ref name="ZiagenPI">Ziagen (abacavir) [prescribing information]. Research Triangle Park, NC: ViiV Healthcare; 2020.</ref>

==Administration==
Type: Nucleoside reverse transcriptase inhibitor (NRTI)
Dosage Forms: 300 mg scored tablets; 20 mg/mL oral solution
Routes of Administration: Oral
Common Trade Names: Ziagen; also in fixed-dose combinations: Triumeq (abacavir/dolutegravir/lamivudine), Epzicom (abacavir/lamivudine), Trizivir (abacavir/lamivudine/[[Zidovudine|zidovudine]])

==Adult Dosing==
600 mg PO daily, given as either 300 mg twice daily or 600 mg once daily<ref name="ZiagenPI"/>
May take with or without food
'''Must screen for HLA-B5701 before initiating''' (see Contraindications/Comments)<ref name="ZiagenPI"/>

==Pediatric Dosing==
Approved for patients ≥3 months<ref name="ZiagenPI"/>
8 mg/kg PO twice daily or 16 mg/kg PO once daily (max 600 mg/day)
Scored tablets may be used for children ≥14 kg; oral solution for younger/smaller children

==Special Populations==
===[[Drug pregnancy categories|Pregnancy Rating]]===
Formerly Category C; no adequate controlled studies in pregnant women<ref name="ZiagenPI"/>
Crosses the placenta; no increased birth defect rate observed in registry data
Antiretroviral Pregnancy Registry: 1-800-258-4263

===Lactation risk===
Unknown whether excreted in human milk; women with HIV should not breastfeed (risk of HIV transmission)<ref name="ZiagenPI"/>

===Renal Dosing===
*Adult: No dose adjustment needed (primarily hepatically metabolized; ~2% unchanged drug in urine)<ref name="ZiagenPI"/>
**Not known if removed by dialysis
Pediatric: No specific data

===Hepatic Dosing===
Adult:<ref name="ZiagenPI"/>
Mild impairment (Child-Pugh A): '''200 mg PO twice daily''' (reduced dose; use oral solution to enable this)
Moderate or severe impairment (Child-Pugh B or C): '''Contraindicated'''
Pediatric: Not studied

==Contraindications==
Allergy to class/drug
'''HLA-B5701-positive''' patients<ref name="ZiagenPI"/>
Prior hypersensitivity reaction to abacavir ('''NEVER rechallenge''')<ref name="ZiagenPI"/>
Moderate or severe hepatic impairment (Child-Pugh B or C)<ref name="ZiagenPI"/>

==Adverse Reactions==
===Serious===
'''Hypersensitivity reaction (Boxed Warning):''' Multi-organ syndrome occurring in ~8% without HLA screening (~1% with screening). Median onset 9 days (range: within first 6 weeks, though can occur any time). Presents with ≥2 of the following symptom groups:<ref name="ZiagenPI"/><ref name="HLA">Abacavir Therapy and HLA-B57:01 Genotype. ''Medical Genetics Summaries''. NCBI Bookshelf. Updated 2025.</ref>
'''Group 1:''' Fever
'''Group 2:''' Rash (maculopapular or urticarial)
'''Group 3:''' GI (nausea, vomiting, diarrhea, abdominal pain)
'''Group 4:''' Constitutional (malaise, fatigue, body aches)
'''Group 5:''' Respiratory (dyspnea, cough, pharyngitis)
Symptoms '''worsen with each subsequent dose''' and resolve within 72 hours of stopping
**'''Rechallenge after hypersensitivity can cause fatal hypotension, multi-organ failure, and death within hours'''<ref name="ZiagenPI"/>
'''Lactic acidosis with hepatic steatosis''' (NRTI class effect; including fatal cases)<ref name="ZiagenPI"/>
[[Immune reconstitution syndrome|Immune reconstitution inflammatory syndrome (IRIS)]]

===Common===
Nausea, headache, malaise, fatigue, diarrhea, loss of appetite (each ≥10%)<ref name="ZiagenPI"/>
Insomnia, abnormal dreams

==Pharmacology==
Half-life: ~1.5 hours (plasma); intracellular carbovir triphosphate half-life ~21 hours (supports once-daily dosing)<ref name="ZiagenPI"/>
Metabolism: Hepatic via alcohol dehydrogenase and glucuronyltransferase; not a CYP450 substrate and does not significantly inhibit or induce CYP enzymes<ref name="ZiagenPI"/>
Excretion: ~83% urine (as metabolites; ~2% unchanged), ~16% feces<ref name="ZiagenPI"/>

==Mechanism of Action==
Abacavir is a guanosine analog that is intracellularly phosphorylated to its active metabolite, carbovir triphosphate. Carbovir triphosphate competes with the natural substrate deoxyguanosine triphosphate (dGTP) for incorporation by HIV-1 reverse transcriptase. Once incorporated into viral DNA, it acts as a chain terminator due to the absence of a 3'-hydroxyl group, halting proviral DNA synthesis.<ref name="ZiagenPI"/>

==Comments==
'''HLA-B5701 screening is mandatory before starting any abacavir-containing product''' — this includes Triumeq, Epzicom, and Trizivir. ~6% of Caucasians and ~2–3% of African Americans carry this allele<ref name="HLA"/>
'''ED hypersensitivity recognition:''' A patient on abacavir presenting with a multi-system illness (fever + rash + GI + respiratory symptoms) should be treated as a suspected abacavir hypersensitivity reaction until proven otherwise. '''Discontinue abacavir immediately''' — do not wait for confirmatory testing. Symptoms classically worsen with each dose and improve within 72 hours of stopping<ref name="ZiagenPI"/>
'''NEVER rechallenge:''' Restarting abacavir after a hypersensitivity reaction — even after resolution — can cause '''fatal anaphylaxis within hours''' (hypotension, renal failure, death). This applies regardless of HLA-B5701 status<ref name="ZiagenPI"/>
'''Mimics of other diagnoses:''' Abacavir hypersensitivity can be misdiagnosed as pneumonia, flu, gastroenteritis, or drug reaction to other agents. If in doubt, stop abacavir and consult [[HIV - AIDS (main)|HIV/ID]]
'''Ethanol interaction:''' Alcohol decreases elimination of abacavir (competition for alcohol dehydrogenase) — increases abacavir exposure by ~41%. No dose adjustment recommended, but be aware in heavy drinkers<ref name="ZiagenPI"/>
'''Low drug interaction profile:''' Abacavir is not metabolized by CYP450 and does not significantly affect other drug levels — one of the safest NRTIs from an interaction standpoint when prescribing in the ED
'''Cardiovascular risk:''' Some observational data suggested increased MI risk with abacavir use; this remains controversial and has not been confirmed in randomized trials. The FDA has not added a cardiovascular warning<ref name="ZiagenPI"/>
Overdose: No specific antidote; supportive care. Not known if removed by dialysis<ref name="ZiagenPI"/>

==See Also==
[[HIV - AIDS (main)]]
[[HIV post-exposure prophylaxis]]
[[Immune reconstitution syndrome]]
[[Emtricitabine/tenofovir]]
[[Dolutegravir]]

==References==
{{reflist|2}}
[[Category:Pharmacology]]