CLONIDINE HYDROCHLORIDE

CLONIDINE HYDROCHLORIDE (kloe'ni-deen) Catapres, Catapres-TTS, Dixaril , Duraclon Classifications: central-acting antihypertensive; analgesic; Therapeutic: antihypertensive, central-acting; analgesic Prototype: Methyldopa Pregnancy Category: C

Availability

0.1 mg, 0.2 mg, 0.3 mg tablets; 0.1 mg/24 h, 0.2 mg/24 h, 0.3 mg/24 h transdermal patch; 100 mcg/mL, 500 mcg/mL injection

Action

Centrally acting antiadrenergic derivative. Stimulates alpha₂-adrenergic receptors in CNS to inhibit sympathetic vasomotor centers. Central actions reduce plasma concentrations of norepinephrine. It decreases systolic and diastolic BP and heart rate. Orthostatic effects tend to be mild and occur infrequently.

Therapeutic Effect

Decreases systolic and diastolic BP and heart rate. Reportedly minimizes or eliminates many of the common clinical S&S associated with withdrawal of heroin, methadone, or other opiates.

Uses

Step 2 drug in stepped-care approach to treatment of hypertension, either alone or with diuretic or other antihypertensive agents. Epidural administration as adjunct therapy for severe pain.

Unlabeled Uses

Prophylaxis for migraine; treatment of dysmenorrhea, menopausal flushing, diarrhea, paroxysmal localized hyperhidroses; alcohol, smoking, opiate, and benzodiazepine withdrawal; in the clonidine suppression test for diagnosis of pheochromocytoma; Gilles de la Tourette syndrome; attention deficit disorder with hyperactivity (ADDH) in children.

Contraindications

Anticoagulant therapy, coagulopathy; use of clonidine patch in polyarteritis nodosa, scleroderma, SLe on affected areas; pregnancy (category C), lactation.

Cautious Use

Severe coronary insufficiency, recent MI, sinus node dysfunction, cerebrovascular disease; diabetes mellitus; older adult; chronic renal failure; Raynaud's disease, thromboangiitis obliterans; history of major depression.

Route & Dosage

Hypertension Adult: PO 0.1 mg b.i.d. or t.i.d., may increase by 0.1–0.2 mg/d until desired response is achieved (max: 2.4 mg/d) Transdermal 0.1 mg patch once q7d, may increase by 0.1 mg q1–2 wk Geriatric: PO Start with 0.1 mg once daily Child: PO 5–10 mcg/kg/d divided q8–12h, may increase to 5–25 mcg/kg/d divided q6h (max: 0.9 mg/d) Severe Pain Adult: Epidural Start infusion at 30 mcg/h and titrate to response. Use rates >40 mcg/h with caution Child: Epidural Start infusion at 0.5 mcg/kg/h and titrate to response ADDH Child: PO 5 mcg/kg/d in 4 divided doses (average dose, 0.15–0.2 mg/d) Transdermal 0.2–0.3 mg/d q5–7d

Administration

• Give last PO dose immediately before patient retires to ensure overnight BP control and to minimize daytime drowsiness.
• Oral dosage is increased gradually over a period of weeks so as not to lower BP abruptly (especially important in the older adult). Follow-up visits should be scheduled every 2–4 wk until BP stabilizes, then every 2–4 mo.
• Apply transdermal patch to dry skin, free of hair and rash. Avoid irritated, abraded, or scarred skin. Recommended areas for applying transdermal patch are upper outer arm and anterior chest. Less drug is absorbed from thighs. Rotate application sites and keep a record.
• During change from PO clonidine to transdermal system, PO clonidine should be maintained for at least 24 h after patch is applied. Consult physician.
• Do not abruptly discontinue drug. It should be withdrawn over a period of 2–4 d. Abrupt withdrawal resembles sympathetic stimulation and may result in restlessness and headache 2–3 h after a missed dose and a hypertensive crisis within 8–18 h.
• Store in tightly closed container at 15°–30° C (59°–86° F) unless otherwise directed.

Adverse Effects (≥1%)

CV: Hypotension (epidural), postural hypotension (mild), peripheral edema, ECG changes, tachycardia, bradycardia, flushing, rapid increase in BP with abrupt withdrawal. GI: Dry mouth, constipation, abdominal pain, pseudo-obstruction of large bowel, altered taste, nausea, vomiting, hepatitis, hyperbilirubinemia, weight gain (sodium retention). CNS: Drowsiness, sedation, dizziness, headache, fatigue, weakness, sluggishness, dyspnea, vivid dreams, nightmares, insomnia, behavior changes, agitation, hallucination, nervousness, restlessness, anxiety, mental depression. Skin: Rash, pruritus, thinning of hair, exacerbation of psoriasis; with transdermal patch: hyperpigmentation, recurrent herpes simplex, skin irritation, contact dermatitis, mild erythema. Special Senses: Dry eyes. Urogenital: Impotence, loss of libido.

Diagnostic Test Interference

Avoid use of transdermal patch during MRI. Possibility of decreased urinary excretion of aldosterone, catecholamines, and VMA (however, sudden withdrawal of clonidine may cause increases in these values); transient increases in blood glucose; weakly positive direct antiglobulin (Coombs') tests.

Interactions

Drug: Alcohol and other cns depressants add to CNS depression; tricyclic antidepressants may reduce antihypertensive effects. opiate analgesics increase hypotension with epidural clonidine. Increased risk of bradycardia or AV block when epidural clonidine is used with digoxin, calcium channel blockers, or beta-blockers.

Pharmacokinetics

Absorption: Readily absorbed from GI tract. Onset: 30–60 min PO; 1–3 d transdermal. Peak: 2–4 h PO; 2–3 d transdermal. Duration: 8 h PO; 7 d transdermal. Distribution: Widely distributed; crosses blood–brain barrier; not known if crosses placenta or distributed into breast milk. Metabolism: In liver. Elimination: 80% in urine, 20% in feces. Half-Life: 6–20 h.

Nursing Implications

Assessment & Drug Effects

• Monitor BR closely. Determine positional changes (supine, sitting, standing).
• With epidural administration, frequently monitor BP and HR. Hypotension is a common side effect that may require intervention.
• Monitor BP closely whenever a drug is added to or withdrawn from therapeutic regimen.
• Monitor I&O during period of dosage adjustment. Report change in I&O ratio or change in voiding pattern.
• Determine weight daily. Patients not receiving a concomitant diuretic agent may gain weight, particularly during first 3 or 4 d of therapy, because of marked sodium and water retention.
• Supervise closely patients with history of mental depression, as they may be subject to further depressive episodes.

Patient & Family Education

• Although postural hypotension occurs infrequently, make position changes slowly, and in stages, particularly from recumbent to upright position, and dangle and move legs a few minutes before standing. Lie down immediately if faintness or dizziness occurs.
• Avoid potentially hazardous activities until reaction to drug has been determined due to possible sedative effects.
• Do not omit doses or stop the drug without consulting the physician.
• Do not take OTC medications, alcohol, or other CNS depressants without prior discussion with physician.
• Examine site when transdermal patch is removed and report to physician if erythema, rash, irritation, or hyperpigmentation occurs.
• If transdermal patch loosens, tape it in place with adhesive. The patch should never be cut or trimmed.

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Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug