PRECAUTIONS General In patients who have developed localized contact sensitization to clonidine transdermal system, continuation of clonidine transdermal system or substitution of oral clonidine hydrochloride therapy may be associated with development of a generalized skin rash. In patients who develop an allergic reaction to clonidine transdermal system, substitution of oral clonidine hydrochloride may also elicit an allergic reaction (including generalized rash, urticaria, or angioedema). The sympatholytic action of clonidine may worsen sinus node dysfunction and atrioventricular (AV) block, especially in patients taking other sympatholytic drugs. There are postmarketing reports of patients with conduction abnormalities and/or taking other sympatholytic drugs who developed severe bradycardia requiring IV atropine, IV isoproterenol and temporary cardiac pacing while taking clonidine. In hypertension caused by pheochromocytoma, no therapeutic effect of clonidine transdermal system can be expected. In rare instances, loss of blood pressure control has been reported in patients using clonidine transdermal system according to the instructions for use. Perioperative Use Clonidine transdermal system therapy should not be interrupted during the surgical period. Blood pressure should be carefully monitored during surgery and additional measures to control blood pressure should be available if required. Physicians considering starting clonidine transdermal system therapy during the perioperative period must be aware that therapeutic plasma clonidine levels are not achieved until 2 to 3 days after initial application of clonidine transdermal system (see DOSAGE AND ADMINISTRATION ). Defibrillation or Cardioversion The transdermal clonidine systems should be removed before attempting defibrillation or cardioversion because of the potential for altered electrical conductivity, which may increase the risk of arcing, a phenomenon associated with the use of defibrillators. MRI Skin burns have been reported at the patch site in several patients wearing an aluminized transdermal system during a magnetic resonance imaging scan (MRI). Because the clonidine transdermal system patch contains aluminum, it is recommended to remove the system before undergoing an MRI. Information for Patients Patients should be cautioned against interruption of clonidine transdermal system therapy without their physician's advice. Since patients may experience a possible sedative effect, dizziness, or accommodation disorder with use of clonidine, caution patients about engaging in activities such as driving a vehicle or operating appliances or machinery. Also, inform patients that this sedative effect may be increased by concomitant use of alcohol, barbiturates, or other sedating drugs. Patients who wear contact lenses should be cautioned that treatment with clonidine transdermal system may cause dryness of eyes. Patients should be instructed to consult their physicians promptly about the possible need to remove the patch if they observe moderate to severe localized erythema and/or vesicle formation at the site of application or generalized skin rash. If a patient experiences isolated, mild localized skin irritation before completing 7 days of use, the system may be removed and replaced with a new system applied to a fresh skin site. If the system should begin to loosen from the skin after application, the patient should be instructed to place the adhesive cover directly over the system to ensure adhesion during its 7 day use. Used clonidine transdermal system patches contain a substantial amount of their initial drug content which may be harmful to infants and children if accidentally applied or ingested. THEREFORE, PATIENTS SHOULD BE CAUTIONED TO KEEP BOTH USED AND UNUSED CLONIDINE TRANSDERMAL SYSTEM PATCHES OUT OF THE REACH OF CHILDREN. After use, clonidine transdermal system should be folded in half with the adhesive sides together and discarded away from children's reach. Instructions for use, storage and disposal of the system are provided at the end of this brochure. These instructions are also included in each box of clonidine transdermal system. Drug Interactions Clonidine may potentiate the CNS-depressive effects of alcohol, barbiturates or other sedating drugs. If a patient receiving clonidine is also taking tricyclic antidepressants, the hypotensive effect of clonidine may be reduced, necessitating an increase in the clonidine dose. If a patient receiving clonidine is also taking neuroleptics, orthostatic regulation disturbances (e.g., orthostatic hypotension, dizziness, fatigue) may be induced or exacerbated. Monitor heart rate in patients receiving clonidine concomitantly with agents known to affect sinus node function or AV nodal conduction, e.g., digitalis, calcium channel blockers, and beta-blockers. Sinus bradycardia resulting in hospitalization and pacemaker insertion has been reported in association with the use of clonidine concomitantly with diltiazem or verapamil. Amitriptyline in combination with clonidine enhances the manifestation of corneal lesions in rats (see Toxicology ). Toxicology In several studies with oral clonidine hydrochloride, a dose-dependent increase in the incidence and severity of spontaneous retinal degeneration was seen in albino rats treated for six months or longer. Tissue distribution studies in dogs and monkeys showed a concentration of clonidine in the choroid. In view of the retinal degeneration seen in rats, eye examinations were performed during clinical trials in 908 patients before, and periodically after, the start of clonidine therapy. In 353 of these 908 patients, the eye examinations were carried out over periods of 24 months or longer. Except for some dryness of the eyes, no drug-related abnormal ophthalmological findings were recorded and, according to specialized tests such as electroretinography and macular dazzle, retinal function was unchanged. In combination with amitriptyline, clonidine hydrochloride administration led to the development of corneal lesions in rats within 5 days. Carcinogenesis, Mutagenesis, Impairment of Fertility Chronic dietary administration of clonidine was not carcinogenic to rats (132 weeks) or mice (78 weeks) dosed, respectively, at up to 46 to 70 times the maximum recommended daily human dose as mg/kg (9 or 6 times the MRDHD on a mg/m2 basis). There was no evidence of genotoxicity in the Ames test for mutagenicity or mouse micronucleus test for clastogenicity. Fertility of male and female rats was unaffected by clonidine doses as high as 150 mcg/kg (approximately 3 times the MRDHD). In a separate experiment, fertility of female rats appeared to be affected at dose levels of 500 to 2000 mcg/kg (10 to 40 times the oral MRDHD on a mg/kg basis; 2 to 8 times the MRDHD on a mg/m2 basis). Pregnancy Teratogenic Effects Pregnancy Category C Reproduction studies performed in rabbits at doses up to approximately 3 times the oral maximum recommended daily human dose (MRDHD) of clonidine hydrochloride produced no evidence of a teratogenic or embryotoxic potential in rabbits. In rats, however, doses as low as 1/3 the oral MRDHD (1/15 the MRDHD on a mg/m2 basis) of clonidine were associated with increased resorptions in a study in which dams were treated continuously from 2 months prior to mating. Increased resorptions were not associated with treatment at the same or at higher dose levels (up to 3 times the oral MRDHD) when the dams were treated on gestation days 6 to 15. Increases in resorption were observed at much higher dose levels (40 times the oral MRDHD on a mg/kg basis; 4 to 8 times the MRDHD on a mg/m2 basis) in mice and rats treated on gestation days 1 to 14 (lowest dose employed in the study was 500 mcg/kg). No adequate well-controlled studies have been conducted in pregnant women. Clonidine crosses the placental barrier (see CLINICAL PHARMACOLOGY, Pharmacokinetics ). Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed. Nursing Mothers As clonidine is excreted in human milk, caution should be exercised when clonidine transdermal system is administered to a nursing woman. Pediatric Use Safety and effectiveness in pediatric patients have not been established in adequate and well-controlled trials.