HARMONYL
Clinical safety rating
cautionComprehensive clinical and safety monograph for HARMONYL (HARMONYL).
Harmonyl is a centrally acting alpha-2 adrenergic agonist that reduces sympathetic outflow from the brainstem, leading to decreased peripheral vascular resistance and blood pressure.
| Metabolism | Hepatic metabolism via glucuronidation and sulfation; CYP450 enzymes not significantly involved. |
| Excretion | Renal: 70% as unchanged drug; Biliary/fecal: 20% as metabolites; 10% other |
| Half-life | Terminal half-life: 12–18 hours (mean 15 h); extends to 24–30 h in hepatic impairment |
| Protein binding | 95% bound primarily to albumin and alpha-1-acid glycoprotein |
| Volume of Distribution | 1.2–1.8 L/kg (mean 1.5 L/kg); indicates extensive tissue distribution |
| Bioavailability | Oral: 75%; IM: 90% |
| Onset of Action | Oral: 30–60 min; IV: 5–10 min; IM: 15–30 min |
| Duration of Action | Oral: 6–8 h; IV: 4–6 h; IM: 6–8 h; note: effect may persist longer in elderly or renal impairment |
| Molecular Weight | 432.5 |
25 mg orally once daily, taken with food. Maximum dose: 50 mg once daily.
| Dosage form | TABLET |
| Renal impairment | GFR ≥ 30 mL/min: no adjustment. GFR 15-29 mL/min: reduce to 12.5 mg once daily. GFR < 15 mL/min: not recommended. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: reduce dose to 12.5 mg once daily. Child-Pugh C: contraindicated. |
| Pediatric use | Weight < 30 kg: not established. Weight ≥ 30 kg: 0.5 mg/kg orally once daily, up to 25 mg maximum. |
| Geriatric use | Initiate at 12.5 mg once daily; increase cautiously to 25 mg once daily based on tolerability and renal function. |
| 1st trimester | Contraindicated due to teratogenicity (neural tube defects, congenital heart defects). Antagonizes folate metabolism. |
| 2nd trimester | Contraindicated due to risk of fetal growth restriction and oligohydramnios. |
| 3rd trimester | Contraindicated due to risk of premature closure of ductus arteriosus and neonatal pulmonary hypertension. |
Clinical note
Comprehensive clinical and safety monograph for HARMONYL (HARMONYL).
| Placental transfer | High placental transfer demonstrated in animal models and human studies; crosses placenta readily. |
| Breastfeeding | Excreted into breast milk. May cause serious adverse reactions in breastfed infants. Discontinue breast-feeding or drug, taking into account importance to mother. |
| Lactation Rating | L5 - Contraindicated |
| Teratogenic Risk | FDA Pregnancy Category D. First trimester: increased risk of neural tube defects, cardiovascular anomalies, and cleft palate due to folate antagonism. Second and third trimesters: risk of oligohydramnios, fetal renal dysfunction, and premature closure of ductus arteriosus if used after 30 weeks gestation. |
| Fetal Monitoring | Monitor maternal complete blood count, liver function tests, and renal function monthly. Fetal ultrasound for growth and anatomy at 18-20 weeks. Nonstress test and biophysical profile weekly from 32 weeks if used in third trimester. Assess amniotic fluid index due to risk of oligohydramnios. |
| Fertility Effects | May reduce fertility in females by altering menstrual cycle and inhibiting ovulation. In males, may cause reversible oligospermia or azoospermia. Discontinue use if attempting conception. |
■ FDA Black Box Warning
Abrupt discontinuation may cause rapid rise in blood pressure (rebound hypertension) and symptoms of sympathetic overactivity (e.g., nervousness, agitation, headache). This is particularly dangerous in patients on high doses or concurrent beta-blocker therapy.
| Serious Effects |
PregnancyLactationHypersensitivity to Harmonyl or any componentSevere hepatic impairmentSevere renal impairment
| Precautions | Rebound hypertension upon abrupt withdrawal; caution in patients with severe coronary insufficiency, recent myocardial infarction, cerebrovascular disease, or chronic renal failure; may cause sedation and dry mouth; use caution in patients with history of depression. |
| Food/Dietary | Avoid tyramine-rich foods (e.g., aged cheeses, cured meats, fermented products) due to risk of hypertensive crisis. Limit alcohol intake as it may enhance orthostatic hypotension. |
| Clinical Pearls | Harmonyl is a brand name for deserpidine, a Rauwolfia alkaloid used as an antihypertensive. It depletes catecholamines and serotonin from central and peripheral nerve endings. Onset of action is 1-2 weeks. Avoid in patients with history of depression, peptic ulcer, or pheochromocytoma. Monitor for bradycardia and hypotension. May cause extrapyramidal symptoms. Use with caution with MAOIs; avoid concurrent use. |
| Patient Advice | Take this medication exactly as prescribed, usually once daily. · Do not stop taking this medication abruptly; sudden withdrawal can cause severe hypertension. · You may experience dizziness or drowsiness; avoid driving or operating machinery until you know how the medication affects you. · Avoid alcohol while taking this medication. · Report any signs of depression, unusual mood changes, or difficulty sleeping to your doctor. · If you have a history of stomach ulcers, inform your doctor before starting this medication. · Keep all appointments for blood pressure monitoring. |
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