XANAX XR
Clinical safety rating: caution
Comprehensive clinical and safety monograph for XANAX XR (XANAX XR).
Benzodiazepine that enhances GABA-A receptor activity by increasing the frequency of chloride channel opening, leading to neuronal hyperpolarization and reduced excitability.
| Metabolism | Hepatic via CYP3A4; active metabolite alprazolam does not accumulate significantly. |
| Excretion | Renal excretion of unchanged drug and metabolites accounts for approximately 80-90% of the dose. Fecal excretion is minimal (<10%). |
| Half-life | Mean terminal elimination half-life is 11.2 hours (range 6.3-15.8 hours). The extended-release formulation provides sustained therapeutic concentrations with once-daily dosing. |
| Protein binding | 80% bound to serum albumin. |
| Volume of Distribution | Approximately 1.1 L/kg (range 0.9-1.3 L/kg), indicating extensive tissue distribution. |
| Bioavailability | Oral: Approximately 90% (absolute bioavailability). |
| Onset of Action | Oral: Onset of anxiolytic effect occurs within 1-2 hours post-dose due to extended-release properties with peak concentrations at ~1.5-2 hours. |
| Duration of Action | Duration of anxiolytic effect is approximately 24 hours with once-daily dosing. Steady-state is achieved within 2-3 days. |
| Molecular Weight | 308.77 |
0.5-1 mg orally once daily; may increase at 3-4 day intervals; maximum 10 mg/day
| Dosage form | TABLET, EXTENDED RELEASE |
| Renal impairment | GFR 30-89 mL/min: no adjustment; GFR 15-29 mL/min: initiate at 0.5 mg once daily, titrate cautiously; GFR <15 mL/min: avoid use |
| Liver impairment | Child-Pugh Class A: initiate 0.5 mg once daily; Child-Pugh Class B: initiate 0.25 mg once daily; Child-Pugh Class C: avoid use |
| Pediatric use | Not FDA approved for patients <18 years; off-label doses: 0.125-0.5 mg/kg/day divided once daily; titrate slowly |
| Geriatric use | Initiate 0.25 mg once daily; titrate by 0.125 mg increments every 3-4 days; maximum 2 mg/day |
| 1st trimester | Associated with increased risk of congenital malformations, particularly cleft lip/palate, if used during first trimester. Use only if potential benefit outweighs risk. |
| 2nd trimester | May cause fetal adverse effects; use only if clearly needed. Monitor for CNS depression and neonatal withdrawal. |
| 3rd trimester | Risk of neonatal withdrawal and CNS depression (floppy infant syndrome) if used near term. Avoid during labor and delivery. |
Clinical note
Comprehensive clinical and safety monograph for XANAX XR (XANAX XR).
| Placental transfer | Alprazolam crosses the placenta with fetal serum concentrations approximately equal to maternal levels. Transplacental passage occurs via passive diffusion. |
| Breastfeeding | Alprazolam is excreted into breast milk in low amounts; however, accumulation can occur in neonates due to long half-life. Observe infant for sedation, poor feeding, and weight loss. Consider risk-benefit; alternative agents may be preferred. |
■ FDA Black Box Warning
Concomitant use with opioids may result in profound sedation, respiratory depression, coma, and death; reserve for patients with inadequate alternative treatment options.
| Serious Effects |
Acute narrow-angle glaucomaConcomitant use with ketoconazole, itraconazole, or other potent CYP3A4 inhibitorsKnown hypersensitivity to benzodiazepinesSevere hepatic impairmentMyasthenia gravisSleep apneaSevere respiratory insufficiency
| Precautions | Risks of dependence and withdrawal reactions, Risk of abuse and misuse, Concomitant use with CNS depressants, Risk of severe anaphylactic reactions, Use in patients with depression or suicidal ideation |
| Food/Dietary | Grapefruit and grapefruit juice may increase alprazolam levels; avoid concurrent consumption. Alcohol intake should be strictly avoided due to additive CNS depressant effects. Take with or without food; however, high-fat meals may delay absorption but not the extent. |
Loading safety data…
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | First trimester: Increased risk of oral cleft (absolute risk 0.5-1% vs 0.1-0.2% background). Second and third trimesters: Risk of floppy infant syndrome, withdrawal symptoms, respiratory depression, and neonatal sedation. Late third trimester or delivery: Risk of neonatal withdrawal and hypotonia. |
| Fetal Monitoring | Monitor maternal sedation, respiratory rate, and CNS depression. Fetal monitoring for growth restriction and preterm labor. Assess neonatal Apgar scores, respiratory effort, and signs of withdrawal or sedation after delivery. |
| Fertility Effects | May cause menstrual irregularities, anovulation, and decreased libido due to CNS depression and potential hyperprolactinemia. Reversible upon discontinuation. |
| Clinical Pearls | XANAX XR (alprazolam extended-release) is indicated for panic disorder with or without agoraphobia. Due to its extended-release formulation, it has a slower onset and longer duration compared to immediate-release alprazolam. Dose conversion from immediate-release is not 1:1; total daily dose of immediate-release should be given once daily of XR. Avoid abrupt discontinuation to prevent withdrawal symptoms, including seizures. Monitor for CNS depression when co-administered with other CNS depressants. Use cautiously in patients with hepatic impairment or elderly due to reduced clearance. |
| Patient Advice | Take this medication exactly as prescribed, usually once daily in the morning. · Do not crush, chew, or break the extended-release tablets; swallow them whole. · Avoid alcohol and other CNS depressants while taking XANAX XR, as they can increase drowsiness and risk of overdose. · Do not stop taking this medication abruptly without consulting your doctor; withdrawal symptoms can occur. · This medication can be habit-forming; use only as directed and do not share with others. · Inform your doctor if you become pregnant or plan to become pregnant, as use during pregnancy may harm the fetus. |