ABACAVIR || DOLUTEGRAVIR || LAMIVUDINE
Clinical safety rating: safe
Trimethoprim/sulfamethoxazole increases lamivudine exposure Severe acute exacerbations of hepatitis B have been reported upon discontinuation.
Abacavir is a carbocyclic synthetic nucleoside analog guanosine reverse transcriptase inhibitor (NRTI) that inhibits HIV-1 reverse transcriptase. Dolutegravir is an HIV-1 integrase strand transfer inhibitor (INSTI) that blocks viral integration into host DNA. Lamivudine is a synthetic nucleoside analog cytosine reverse transcriptase inhibitor (NRTI) that inhibits HIV-1 reverse transcriptase.
| Metabolism | Data not established |
| Excretion | Abacavir: 83% renal (primarily as metabolites via alcohol dehydrogenase and glucuronidation), 16% fecal. Dolutegravir: 64% fecal (unchanged), 32% renal (minor as metabolites via UGT1A1 and CYP3A4). Lamivudine: >70% renal (unchanged via organic cation transport). |
| Half-life | Abacavir: 1.5 hr (terminal half-life ~1.5 hr, but intracellular carbovir-TP half-life ~12-20 hr supports once-daily dosing). Dolutegravir: ~14 hr (terminal half-life, clinical context: once-daily dosing due to long intracellular half-life and high potency). Lamivudine: 5-7 hr (terminal half-life, intracellular half-life of lamivudine-TP ~18-22 hr supports once-daily dosing). |
| Protein binding | Abacavir: ~49% bound (low affinity to albumin). Dolutegravir: ≥99% bound (primarily albumin and α1-acid glycoprotein). Lamivudine: <36% bound (minimal binding, predominantly albumin). |
| Volume of Distribution | Abacavir: 1.3 L/kg (large Vd, extensive tissue distribution including CNS). Dolutegravir: 12-17 L (approximately 0.2 L/kg based on 70 kg, limited to plasma and extracellular fluid; low Vd due to high protein binding). Lamivudine: 1.3 L/kg (large Vd, evenly distributed throughout total body water, penetrates CSF). |
| Bioavailability | Abacavir: 83% (oral, immediate-release). Dolutegravir: Not established in healthy volunteers due to extensive first-pass metabolism; studies suggest high oral bioavailability with minimal food effect (approximately 95% based on mass balance studies). Lamivudine: 86% (oral, immediate-release, reduced slightly with food). |
| Onset of Action | Oral: Time to antiviral effect not precisely defined; intracellular triphosphate levels peak within 4-8 hr for abacavir, 2-4 hr for dolutegravir (based on HIV RNA decline seen within 1 week). No IV formulation. |
| Duration of Action | Abacavir: Duration of antiviral effect corresponds to intracellular carbovir-TP half-life of ~12-20 hr; clinical suppression maintained with once-daily dosing. Dolutegravir: Duration supports once-daily dosing due to long intracellular half-life and plasma half-life; optimal trough concentration >0.7 μg/mL for virologic suppression. Lamivudine: Duration supports once-daily dosing; residual antiviral activity persists due to long intracellular triphosphate half-life. |
| Molecular Weight | Abacavir: 286.33 Da; Dolutegravir: 419.38 Da; Lamivudine: 229.26 Da |
One tablet (600 mg abacavir, 50 mg dolutegravir, 300 mg lamivudine) orally once daily.
| Dosage form | TABLET |
| Renal impairment | Not recommended for patients with CrCl <30 mL/min. For CrCl 30-49 mL/min: use individual components as fixed-dose combination is not appropriate. For CrCl ≥50 mL/min: no adjustment. |
| Liver impairment | Contraindicated in Child-Pugh class C. Not recommended for Child-Pugh class B due to lack of data; use with caution. No adjustment for Child-Pugh class A. |
| Pediatric use | Approved for children weighing ≥40 kg: one tablet (600/50/300 mg) once daily. For <40 kg, use individual components with weight-based dosing: abacavir 600 mg (or 8 mg/kg up to 600 mg) once daily; dolutegravir weight-based (e.g., 30-40 kg: 35 mg once daily; <30 kg: dosing per specific guidelines); lamivudine 300 mg (or 4 mg/kg up to 300 mg) once daily. |
| Geriatric use | No specific dose adjustments; monitor renal function due to age-related decline. Use with caution in elderly due to potential comorbidities and polypharmacy. |
| 1st trimester | No increased risk of major birth defects in humans; limited data, but generally considered safe. Use if benefit outweighs risk. |
| 2nd trimester | No known fetal risk; often used due to need for viral suppression. Caution in renal impairment. |
| 3rd trimester | No known fetal risk; sufficient data suggest safety. Monitor for mitochondrial toxicity in neonates. |
Clinical note
Trimethoprim/sulfamethoxazole increases lamivudine exposure Severe acute exacerbations of hepatitis B have been reported upon discontinuation.
| FDA category | Human |
| Placental transfer | All three components cross the placenta. Dolutegravir shows high placental transfer (cord blood/maternal plasma ratio ~1.2). Abacavir and lamivudine also cross readily. |
| Breastfeeding |
■ FDA Black Box Warning
Abacavir: Hypersensitivity reactions, including life-threatening reactions, have occurred in patients treated with abacavir. Patients who carry the HLA-B*5701 allele are at higher risk. Discontinue abacavir immediately if hypersensitivity is suspected and never restart abacavir or any abacavir-containing product after a hypersensitivity reaction.
| Common Effects | Hepatitis B |
| Serious Effects |
Hypersensitivity to abacavir (including HLA-B*5701 positive status)Hepatic impairment (Child-Pugh class B or C) for abacavirSevere renal impairment (CrCl <30 mL/min) for lamivudine
| Precautions | Hypersensitivity reactions to abacavir; screen for HLA-B*5701 allele before initiation or when switching from another abacavir-containing product, Hepatotoxicity including hepatic steatosis and hepatic failure; monitor liver function tests, Lactic acidosis/severe hepatomegaly with steatosis, including fatal cases, especially in patients with hepatic disease or risk factors, Immune reconstitution syndrome, Increased risk of myocardial infarction with abacavir (conflicting data; use caution in patients with cardiovascular risk factors), Severe acute exacerbation of hepatitis B in patients co-infected with hepatitis B virus (HBV) who discontinue lamivudine; monitor hepatic function after stopping, Risk of pancreatitis in pediatric patients receiving lamivudine, Weight and lipid profile changes observed with dolutegravir-based regimens, Neural tube defects when dolutegravir is taken at time of conception; avoid in pregnancy unless benefit outweighs risk |
Loading safety data…
| Abacavir and lamivudine are excreted into breast milk at low concentrations; dolutegravir is present but levels are low. Benefits of breastfeeding outweigh risk in HIV+ mothers on effective ART with undetectable viral load, but guidelines recommend formula feeding in resource-rich settings. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | First trimester: Dolutegravir associated with neural tube defects (NTDs) from prospective cohort data (rate 0.19% vs 0.05% background); avoid use at conception and through first trimester. Abacavir and lamivudine: no significant increase in major malformations. Second and third trimesters: No evidence of fetotoxicity from dolutegravir; abacavir and lamivudine considered safe. Late pregnancy: Dolutegravir may cause hyperbilirubinemia in neonate (case reports). |
| Fetal Monitoring | Maternal: Liver function tests (LFTs), renal function, CBC, HIV RNA viral load every 1-3 months; HLAB*5701 screening before abacavir use. Fetal: First trimester ultrasound for neural tube defects (if dolutegravir exposure); standard anomaly scan at 18-20 weeks. Neonatal: Monitor for hyperbilirubinemia (dolutegravir) and glucose-6-phosphate dehydrogenase (G6PD) deficiency-related hemolysis (abacavir/lamivudine). |
| Fertility Effects | No evidence of adverse effects on fertility in males or females. Dolutegravir did not impair spermatogenesis in animal studies. Abacavir and lamivudine not associated with reproductive toxicity. |
| Food/Dietary | No significant food interactions; absorption of abacavir, dolutegravir, and lamivudine is not affected by food. However, dolutegravir should be taken separately from calcium or iron supplements (at least 2 hours before or 6 hours after). |
| Clinical Pearls | Abacavir is associated with a hypersensitivity reaction in HLA-B*5701-positive patients; screen before initiation. Dolutegravir can cause neural tube defects when used in women of childbearing potential without effective contraception; avoid in first trimester. Lamivudine has activity against both HIV and HBV; be aware of HBV flare upon discontinuation. All three drugs have low potential for drug-drug interactions due to limited CYP450 involvement. |
| Patient Advice | Report any symptoms of hypersensitivity (fever, rash, nausea, vomiting, fatigue) immediately; do not restart abacavir if hypersensitivity reaction occurs. · If you become pregnant or plan to become pregnant while taking dolutegravir, inform your doctor immediately. · Do not stop lamivudine without consulting your doctor if you have hepatitis B; stopping can cause a serious flare of hepatitis. · Take this medication with or without food. If you miss a dose, take it as soon as you remember, but do not double the next dose. · Regular blood tests are needed to monitor viral load, CD4 count, and liver function. |