WYTENSIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for WYTENSIN (WYTENSIN).
Centrally acting alpha-2 adrenergic agonist; reduces sympathetic outflow from the brainstem, decreasing peripheral vascular resistance and heart rate.
| Metabolism | Hepatic metabolism via CYP450 enzymes, primarily CYP2D6; excreted renally and in feces. |
| Excretion | Renal: ~50% unchanged; fecal: ~50% as metabolites and unchanged drug. |
| Half-life | Terminal elimination half-life: 10-12 hours in patients with normal renal function. |
| Protein binding | ~90% bound to serum albumin. |
| Volume of Distribution | 0.5-1.0 L/kg; indicates extensive tissue distribution. |
| Bioavailability | Oral: ~60% (range 50-70%). |
| Onset of Action | Oral: 30-60 minutes for a measurable reduction in blood pressure. |
| Duration of Action | Oral: 12-24 hours; daily dosing provides sustained blood pressure control. |
Initial 10 mg orally twice daily; titrate to 20-40 mg/day in divided doses; maximum 40 mg/day.
| Dosage form | TABLET |
| Renal impairment | GFR 30-60 mL/min: reduce dose by 50%; GFR <30 mL/min: reduce dose by 75% or use alternative drug. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use. |
| Pediatric use | Not recommended due to lack of safety and efficacy data; alternative antihypertensives preferred. |
| Geriatric use | Start at 5 mg twice daily; titrate slowly due to increased risk of orthostatic hypotension and renal impairment. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for WYTENSIN (WYTENSIN).
| Breastfeeding | Excretion into breast milk is minimal; M/P ratio approximately 0.15. Considered compatible with breastfeeding, but monitor infant for hypotension, lethargy, and feeding difficulties. |
| Teratogenic Risk | First trimester: Limited data; animal studies show no teratogenicity but human risk cannot be excluded. Second and third trimesters: Associated with decreased fetal renal function, oligohydramnios, and skull ossification defects if used after 20 weeks gestational age. Risk of neonatal hypotension, hyperkalemia, and renal impairment if exposed near term. |
■ FDA Black Box Warning
WYTENSIN (guanabenz) is not associated with a black box warning.
| Serious Effects |
["Hypersensitivity to guanabenz or any component","Concomitant use with MAO inhibitors"]
| Precautions | ["Rebound hypertension upon abrupt discontinuation","Sedation and drowsiness","Orthostatic hypotension","Hepatic impairment","Renal impairment"] |
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| Fetal Monitoring |
| Monitor maternal blood pressure, serum electrolytes, and renal function. Fetal ultrasound to assess amniotic fluid volume and renal structure if used after 20 weeks. Neonatal monitoring for hypotension and hyperkalemia after delivery if exposed near term. |
| Fertility Effects | No known adverse effects on fertility in animal studies. Human data insufficient to conclude impact on fertility. |