Ultrarapid Metabolizer
Clinical Implication
- Increased CYP2B6 enzyme activity.
- Slightly lower dose-adjusted trough concentrations.
Therapeutic Recommendation
- Initiate efavirenz with standard dosing (600 mg/day).
Rapid Metabolizer
Clinical Implication
- Increased CYP2B6 enzyme activity.
- Slightly lower dose-adjusted trough concentrations.
Therapeutic Recommendation
- Initiate efavirenz with standard dosing (600 mg/day).
Normal Metabolizer
Clinical Implication
- Normal CYP2B6 enzyme activity.
- Normal response expected.
Therapeutic Recommendation
- Initiate efavirenz with standard dosing (600 mg/day).
Intermediate Metabolizer
Clinical Implication
- Decreased CYP2B6 enzyme activity.
- Increased risk of CNS adverse effects (e.g., insomnia, impaired concentration, psychosis, suicidal ideation, depression).
Therapeutic Recommendation
- Initiate efavirenz with decreased dose of 400 mg/day and consider utilizing therapeutic drug monitoring, if available.
Poor Metabolizer
Clinical Implication
- Little to no CYP2B6 enzyme activity.
- Significantly increased risk of CNS adverse effects (e.g., insomnia, impaired concentration, psychosis, suicidal ideation, depression).
Therapeutic Recommendation
- Initiate efavirenz with decreased dose of 400 or 200 mg/day and consider utilizing therapeutic drug monitoring, if available.
Unable to Genotype or Assay Failure
- The analysis failed to yield an informative result and thus no genotype is reported.
Reference
- Desta Z et al. Clin Pharmacol Ther. 2019 Oct;106(4):726-733. PMID: 31006110.
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