The following adverse reactions have been identified during post-approval use of clonidine hydrochloride extended-release tablets. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. These events exclude those already mentioned in 6.1:
Cardiovascular: Q-T prolongation
The following have been reported with other oral immediate release formulations of clonidine:
Concomitant Drug Name or Drug Class
Increase blood pressure and may counteract clonidine’s hypotensive effects
Monitor blood pressure and adjust as needed
Potentiate clonidine’s hypotensive effects
Monitor blood pressure and adjust as needed
Potentiate sedating effects
Drugs that affect sinus node function or AV
node conduction (e.g., digitalis, calcium channel blockers, beta blockers)
Potentiate bradycardia and risk of AV block
Pregnancy Exposure Registry
There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to ADHD medications, including clonidine hydrochloride extended-release tablets, during pregnancy. Healthcare providers are encouraged to register patients by calling the National Pregnancy Registry for ADHD Medications at 1-866-961-2388 or visiting https://womensmentalhealth.org/adhd-medications/.
Prolonged experience with clonidine in pregnant women over several decades, based on published literature, including controlled trials, a retrospective cohort study and case reports, have not identified a drug associated risk of major birth defects, miscarriage, and adverse maternal or fetal outcomes. In animal embryofetal studies, increased resorptions were seen in rats and mice administered oral clonidine hydrochloride from implantation through organogenesis at 10 and 5 times, respectively, the maximum recommended human dose (MRHD) given to adolescents on a mg/m2 basis. No developmental effects were seen in rabbits administered oral clonidine hydrochloride during organogenesis at doses up to 3 times the MRHD (see Data).
The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriages in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively.
Oral administration of clonidine hydrochloride to pregnant rabbits during the period of embryo/fetal organogenesis at doses of up to 80 mcg/kg/day (approximately 3 times the oral maximum recommended daily dose [MRHD] of 0.4 mg/day given to adolescents on a mg/m2 basis) produced no developmental effects. In pregnant rats, however, doses as low as 15 mcg/kg/day (1/3 the MRHD given to adolescents on a mg/m2 basis) were associated with increased resorptions in a study in which dams were treated continuously from 2 months prior to mating and throughout gestation. Increased resorptions were not associated with treatment at the same or at higher dose levels (up to 3 times the MRHD) when treatment of the dams was restricted to gestation days 6 to 15. Increases in resorptions were observed in both rats and mice at 500 mcg/kg/day (10 and 5 times the MRHD in rats and mice, respectively) or higher when the animals were treated on gestation days 1 to 14; 500 mcg/kg/day was the lowest dose employed in this study.
Based on published lactation studies, clonidine hydrochloride is present in human milk at relative infant doses ranging from 4.1 to 8.4% of the maternal weight-adjusted dosage. Although in most cases, there were no reported adverse effects in breastfed infants exposed to clonidine, there is one case report of sedation, hypotonia, and apnea in an infant exposed to clonidine through breast milk. If an infant is exposed to clonidine hydrochloride through breastmilk, monitor for symptoms of hypotension and bradycardia, such as sedation, lethargy, tachypnea and poor feeding (see Clinical Considerations). The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for clonidine hydrochloride extended-release tablets and any potential adverse effects on the breastfed child from clonidine hydrochloride extended-release tablets or from the underlying maternal condition. Exercise caution when clonidine hydrochloride extended-release tablets are administered to a nursing woman.
Monitor breastfeeding infants exposed to clonidine hydrochloride extended-release tablets through breast milk for symptoms of hypotension and/or bradycardia such as sedation, lethargy, tachypnea, and poor feeding.
Based on findings in Animal studies revealed that clonidine hydrochloride extended-release tablets may impair fertility in females and males of reproductive potential [see Nonclinical Toxicology (13.1)].
The safety and efficacy of clonidine hydrochloride extended-release tablets in the treatment of ADHD have been established in pediatric patients 6 to 17 years of age. Use of clonidine hydrochloride extended-release tablets in pediatric patients 6 to 17 years of age is supported by three adequate and well-controlled studies; a short-term, placebo-controlled monotherapy trial, a short-term adjunctive therapy trial and a longer-term randomized monotherapy trial [see Clinical Studies (14)]. Safety and efficacy in pediatric patients below the age of 6 years has not been established.
Juvenile Animal Data
In studies in juvenile rats, clonidine hydrochloride alone or in combination with methylphenidate had an effect on bone growth at clinically relevant doses and produced a slight delay in sexual maturation in males at 3 times the maximum recommended human dose (MRHD) for clonidine and methylphenidate.
In a study where juvenile rats were treated orally with clonidine hydrochloride from day 21 of age to adulthood, a slight delay in onset of preputial separation (delayed sexual maturation) was seen in males treated with 300 mcg/kg/day, which is approximately 3 times the MRHD of 0.4 mg/day on a mg/m2 basis. The no-effect dose was 100 mcg/kg/day, which is approximately equal to the MRHD. There was no drug effects on fertility or on other measures of sexual or neurobehavioral development.
In a study where juvenile rats were treated with clonidine alone (300 mcg/kg/day) or in combination with methylphenidate (10 mg/kg/day in females and 50/30 mg/kg/day in males; the dose was lowered from 50 to 30 mg/kg/day in males due to self-injurious behavior during the first week of treatment) from day 21 of age to adulthood, decreases in bone mineral density and mineral content were observed in males treated with 300 mcg/kg/day clonidine alone and in combination with 50/30 mg/kg/day methylphenidate and a decrease in femur length was observed in males treated with the combination at the end of the treatment period. These doses are approximately 3 times the MRHD of 0.4 mg/day clonidine and 54 mg/day methylphenidate on a mg/m2 basis. All these effects in male were not reversed at the end of a 4-week recovery period. In addition, similar findings were seen in males treated with a lower dose of clonidine (30 mcg/kg/day) in combination with 50 mg/kg/day of methylphenidate and a decrease in femur length was observed in females treated with clonidine alone at the end of the recovery period. These effects were accompanied by a decrease in body weight gain in treated animals during the treatment period but the effect was reversed at the end of the recovery period. A delay in preputial separation (sexual maturation) was observed in males treated with the combination treatment of 300 mcg/kg/day clonidine and 50/30 mg/kg/day methylphenidate. There was no effect on reproduction or sperm analysis in these males.
The impact of renal impairment on the pharmacokinetics of clonidine in children has not been assessed. The initial dosage of clonidine hydrochloride extended-release tablets should be based on degree of impairment. Monitor patients carefully for hypotension and bradycardia, and titrate to higher doses cautiously. Since only a minimal amount of clonidine is removed during routine hemodialysis, there is no need to give supplemental clonidine hydrochloride extended-release tablets following dialysis.
Clonidine hydrochloride extended-release tablets are not a controlled substance and have no known potential for abuse or dependence.
Clonidine overdose: hypertension may develop early and may be followed by hypotension, bradycardia, respiratory depression, hypothermia, drowsiness, decreased or absent reflexes, weakness, irritability and miosis. The frequency of CNS depression may be higher in children than adults. Large overdoses may result in reversible cardiac conduction defects or dysrhythmias, apnea, coma and seizures. Signs and symptoms of overdose generally occur within 30 minutes to two hours after exposure.
Consult with a Certified Poison Control Center (1-800-222-1222) for up-to-date guidance and advice.
Clonidine Hydrochloride Extended-Release is a centrally acting alpha2 -adrenergic agonist available as 0.1 mg extended-release tablets for oral administration. Each 0.1 mg tablet is equivalent to 0.087 mg of the free base.
The inactive ingredients are colloidal silicon dioxide, hydroxyethyl cellulose, hydroxypropyl cellulose, magnesium stearate, microcrystalline cellulose, and sodium lauryl sulfate. The 0.1 mg tablets also contain red iron oxide and titanium dioxide. The formulation is designed to delay the absorption of active drug in order to decrease peak to trough plasma concentration differences. Clonidine hydrochloride, USP is an imidazoline derivative and exists as a mesomeric compound. The chemical name is 2-(2,6-dichlorophenylamino)-2-imidazoline hydrochloride. The following is the structural formula:
Clonidine hydrochloride, USP is an odorless, bitter, white, crystalline substance soluble in water and alcohol.
Clonidine stimulates alpha2 -adrenergic receptors in the brain. Clonidine is not a central nervous system stimulant. The mechanism of action of clonidine in ADHD is not known.
Clonidine is a known antihypertensive agent. By stimulating alpha2 -adrenergic receptors in the brain stem, clonidine reduces sympathetic outflow from the central nervous system and decreases peripheral resistance, renal vascular resistance, heart rate, and blood pressure.
Single-dose Pharmacokinetics in Adults
Immediate-release clonidine hydrochloride and clonidine hydrochloride extended-release have different pharmacokinetic characteristics; dose substitution on a milligram for milligram basis will result in differences in exposure. A comparison across studies suggests that the Cmax is 50% lower for clonidine hydrochloride extended-release compared to immediate-release clonidine hydrochloride.
Following oral administration of an immediate release formulation, plasma clonidine concentration peaks in approximately 3 to 5 hours and the plasma half-life ranges from 12 to 16 hours. The half-life increases up to 41 hours in patients with severe impairment of renal function. Following oral administration about 40% to 60% of the absorbed dose is recovered in the urine as unchanged drug in 24 hours.
About 50% of the absorbed dose is metabolized in the liver. Although studies of the effect of renal impairment and studies of clonidine excretion have not been performed with clonidine hydrochloride extended-release, results are likely to be similar to those of the immediate release formulation.
The pharmacokinetic profile of clonidine hydrochloride extended-release tablet administration was evaluated in an open-label, three-period, randomized, crossover study of 15 healthy adult subjects who received three single-dose regimens of clonidine: 0.1 mg of clonidine hydrochloride extended-release tablets under fasted conditions, 0.1 mg of clonidine hydrochloride extended-release tablets following a high fat meal, and 0.1 mg of clonidine hydrochloride immediate-release under fasted conditions. Treatments were separated by one-week washout periods.
Mean concentration-time data from the 3 treatments are shown in Table 7 and Figure 1. After administration of clonidine hydrochloride extended-release tablets, maximum clonidine concentrations were approximately 50% of the clonidine hydrochloride immediate-release maximum concentrations and occurred approximately 5 hours later relative to clonidine hydrochloride immediate-release. Similar elimination half-lives were observed and total systemic bioavailability following clonidine hydrochloride extended-release tablets was approximately 89% of that following clonidine hydrochloride immediate-release.
Food had no effect on plasma concentrations, bioavailability, or elimination half-life.
Clonidine Hydrochloride Immediate-Release -Fasted
Clonidine Hydrochloride Extended-Release-Fed
Clonidine Hydrochloride Extended-Release -Fasted
Figure 1: Mean Clonidine Concentration-Time Profiles after Single Dose Administration
Multiple-dose Pharmacokinetics in Children and Adolescents
Plasma clonidine concentrations in children and adolescents (0.1 mg bid and 0.2 mg bid) with ADHD are greater than those of adults with hypertension with children and adolescents receiving higher doses on a mg/kg basis. Body weight normalized clearance (CL/F) in children and adolescents was higher than CL/F observed in adults with hypertension. Clonidine concentrations in plasma increased with increases in dose over the dose range of 0.2 to 0.4 mg/day. Clonidine CL/F was independent of dose administered over the 0.2 to 0.4 mg/day dose range. Clonidine CL/F appeared to decrease slightly with increases in age over the range of 6 to 17 years, and females had a 23% lower CL/F than males. The incidence of “sedation-like” AEs (somnolence and fatigue) appeared to be independent of clonidine dose or concentration within the studied dose range in the titration study. Results from the add-on study showed that clonidine CL/F was 11% higher in patients who were receiving methylphenidate and 44% lower in those receiving amphetamine compared to subjects not on adjunctive therapy.
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