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Clonidine Hydrochloride/Chlorthalidone

Pronouncation: (KLOE-nih-DEEN HIGH-droe-KLOR-ide/klor-THAL-ih-dohn)
Class: Antihypertensive combination

Trade Names:
Clorpres
- Tablets 0.1 mg clonidine and 15 mg chlorthalidone
- Tablets 0.2 mg clonidine and 15 mg chlorthalidone
- Tablets 0.3 mg clonidine and 15 mg chlorthalidone

Mechanism of Action

Pharmacology

Clonidine

Stimulates central alpha-adrenergic receptors to inhibit sympathetic cardioaccelerator and vasoconstrictor centers.

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Chlorthalidone

Inhibits reabsorption of sodium and chloride in the proximal portion of the distal convoluted tubules.

Indications and Usage

Treatment of hypertension; not indicated for initial therapy.

Contraindications

Known hypersensitivity to any component of product or sulfonamide derived drugs.

Dosage and Administration

Adults

PO Once or twice/day from a minimum dose of 0.1 mg clonidine plus 15 mg chlorthalidone to a maximum dose of 0.6 mg clonidine plus 30 mg chlorthalidone.

General Advice

Administer with or without food. Administer with food if GI upset occurs.

Storage/Stability

Store tablets at controlled room temperature (59° to 86°F). Protect from moisture.

Drug Interactions

Alcohol, barbiturates, other sedatives

CNS depressive effects may be enhanced with clonidine.

Antihypertensive agents

Action may be increased or potentiated by chlorthalidone.

Insulin, sulfonylureas (eg, chlorpropamide)

Hypoglycemic effect may be decreased by chlorthalidone, necessitating an increase in dosage.

Lithium

Because renal excretion of lithium may be reduced, avoid use if possible.

Norepinephrine

Arterial responsiveness to norepinephrine may be decreased.

Tricyclic antidepressants

Effects on clonidine may be reduced.

Laboratory Test Interactions

Chlorthalidone may decrease serum protein bound iodine levels without signs of thyroid disturbance.

Adverse Reactions

Cardiovascular

Clonidine

Orthostatic hypotension; palpitations; tachycardia; bradycardia; Raynaud phenomena; CHF; ECG abnormalities; arrhythmias.

Chlorthalidone

Orthostatic hypotension.

CNS

Drowsiness; dizziness; sedation

Clonidine

Malaise; agitation; nervousness; depression; headache; insomnia; vivid dreams; nightmares; restlessness; anxiety; visual and auditory hallucinations; delirium; fatigue; vertigo.

Chlorthalidone

Dizziness; paresthesias; headache; xanthopsia.

Dermatologic

Clonidine

Rash; pruritus; hives; angioneurotic edema; urticaria; alopecia.

Chlorthalidone

Purpura; photosensitivity; rash; urticaria; necrotizing angiitis; toxic epidermal necrolysis.

EENT

Clonidine

Dryness and burning of eyes; blurred vision; dryness of nasal mucosa.

GI

Dry mouth; constipation.

Clonidine

Nausea; vomiting; anorexia.

Chlorthalidone

Anorexia; gastric irritation; nausea; vomiting; cramping; diarrhea; constipation; jaundice; pancreatitis.

Genitourinary

Clonidine

Decreased sexual activity; impotence; loss of libido; nocturia; micturition; urinary retention.

Chlorthalidone

Hyperuricemia; impotence.

Hematologic

Chlorthalidone

Leukopenia; agranulocytosis; thrombocytopenia; aplastic anemia.

Hepatic

Clonidine

Transient abnormalities in LFTs.

Metabolic

Clonidine

Weight gain.

Chlorthalidone

Hyperglycemia; hyperuricemia.

Miscellaneous

Clonidine

Weakness; discontinuation syndrome; muscle and joint pain; cramps of the lower limbs; pallor; weakly positive Coombs test; muscle spasm.

Chlorthalidone

Weakness; restlessness.

Precautions

Monitor

Blood sugar

Monitor blood sugar in diabetic patient when drug is started or dose is changed. Report significant changes to health care provider.

BP

Monitor and record BP and pulse. Should hypotension result, hold medication and notify health care provider.


Pregnancy

Category C .

Lactation

Excreted in breast milk.

Children

Safety and efficacy not established.

Renal Function

Use with caution in patients with severe renal disease.

Hepatic Function

Use with caution, minor alterations of fluid and electrolyte balance may precipitate hepatic coma.

Coronary insufficiency

Use with caution in patients with severe coronary insufficiency, recent MI, or cerebral vascular disease.

Electrolyte abnormalities

Hypokalemia and other electrolyte abnormalities, including hyponatremia and hypochloremic alkalosis, are common while receiving chlorthalidone. Ensure that serum electrolytes and renal function are monitored before starting therapy and periodically thereafter.

Perioperative use

Continue clonidine therapy to within 4 h of surgery and resume as soon as possible thereafter.

Sensitization to transdermal clonidine

General skin rash may develop in patients with localized reaction to the patch if they are switched to oral clonidine.

Systemic lupus erythematosus

May be activated or exacerbated.

Uric acid

Hyperuricemia may occur, or frank gout may be precipitated.

Withdrawal

Discontinue therapy by reducing the dose gradually over 2 to 4 days to avoid rapid increase in BP.

Overdosage

Symptoms

Clonidine

Hypotension, bradycardia, lethargy, irritability, weakness, somnolence, diminished or absent reflexes, miosis, vomiting, hypoventilation, arrhythmias, apnea, seizures, transient hypertension

Chlorthalidone

Nausea, weakness, dizziness, disturbances of electrolyte balance.

Patient Information

  • Explain name, dose, action, and potential side effects of drug.
  • Advise patient to take 1 or 2 times daily as prescribed, without regard to meals.
  • Advise patient to try to take each dose at about the same time every day.
  • Inform patient that drug controls, but does not cure hypertension and to continue taking drug as prescribed even when BP is not elevated.
  • Caution patient not to change the dose or stop taking unless advised by health care provider.
  • Caution patient that if medication is ever stopped, slowly reduce dose over 2 to 4 days. Advise patient that sudden discontinuation may result in withdrawal symptoms, including nervousness, agitation, headache, and rapid rise in BP.
  • Instruct patient to continue taking other BP medications as prescribed by health care provider.
  • Advise patient to monitor and record BP and pulse at home and to inform health care provider if abnormal measurements are noted. Also advise patient to bring record of BP and pulse to each follow-up visit.
  • Caution patient to avoid sudden position changes to prevent orthostatic hypotension.
  • Instruct patient to lie or sit down if experiencing dizziness or lightheadedness when standing.
  • Caution patient that alcohol ingestion, inadequate fluid intake, excessive perspiration, diarrhea, or vomiting can lead to excessive fall in BP, resulting in lightheadedness or fainting.
  • Instruct diabetic patient to monitor blood glucose more frequently when drug is started or dose is changed and to inform health care provider of significant changes in readings.
  • Advise patient that drug may impair judgment, thinking, or motor skills, or cause drowsiness. Use caution while driving or performing other tasks requiring mental alertness until tolerance is determined.
  • Caution patient to avoid unnecessary exposure to UV light (eg, sunlight, tanning booths) and to use sunscreen and wear protective clothing when exposed to UV light to avoid photosensitivity reaction.
  • Emphasize to hypertensive patient importance of other modalities on BP: weight control, regular exercise, smoking cessation, and moderate intake of alcohol and salt.
  • Advise women to notify health care provider if pregnant, planning to become pregnant, or breastfeeding.
  • Instruct patient to report any of these symptoms to health care provider: excess thirst, unexplained tiredness, drowsiness or restlessness, muscle pains or cramps, nausea, vomiting, or increased heart rate.
  • Caution patient to not take any prescription or OTC medications or dietary supplements unless advised by health care provider.
  • Advise patient that follow-up visits and lab tests may be required to monitor therapy and to keep appointments.
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