Guanfacine.doc - Guanfacine(TenexTM Guanfacine ER(Intuniv...

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Guanfacine (Tenex TM ) Guanfacine ER (Intuniv) Classification: 2 Adrenergic Agonist Pharmacology: Guanfacine hydrochloride is a centrally acting antihypertensive which stimulates the 2 adrenergic receptor thereby decreasing the output of the presynaptic norepinephrine neuron. The reduced sympathetic nerve impulses from the vasomotor center to the heart and blood vessels results in a slight reduction in heart rate (5 beats/minute) and peripheral vascular resistance. 1 Other 2 adrenergic agonists such as clonidine have shown beneficial effects as non-first line agents in children with Attention Deficit Hyperactivity Disorder (ADHD). Guanfacine, an agent similar to clonidine may be an alternative based on a longer half-life, decreased sedative and hypotensive properties, and more selective binding profile. It appears that 2 adrenergic agonists may exert psychoactive effects via direct effects on the noradrenergic neurotransmitter system, indirectly affecting serotonin and dopamine transmission. 1,2 In addition, 2 adrenergic agents may decrease tics in children with ADHD and tic disorders. 3 Pharmacokinetics: 2,4 Absorption: Referenced to an intravenous dose of 3 mg, the absolute oral bioavailability of guanfacine is about 80%. The time to peak plasma concentrations (Tmax) occur from 1 to 4 hours with an average of 2.6 hours after single oral doses or at steady state. The area under the concentration-time curve (AUC) increases linearly with the dose. Distribution: The drug is approximately 70% bound to plasma proteins, independent of drug concentration. The whole body volume of distribution is high (a mean of 6.3 L/kg), which suggests a high distribution of drug to the tissues. Metabolism: Metabolism occurs in the liver, primarily to the glucuronide and sulfate of 3-hydroxy guanfacine; oxidized mercapturic acid derivatives and other minor metabolites. It is unclear if metabolites have any pharmacologic activity . 5 Elimination: Guanfacine and its metabolites are excreted primarily in the urine. In individuals with healthy renal function, the average elimination half-life is approximately 17 hours (range, 10 to 30 hours). Approximately 50% (40% to 75%) of the dose is eliminated in the urine as unchanged drug; the remainder is eliminated mostly as conjugates of metabolites produced by oxidative metabolism of the aromatic ring. Indications: 2 Guanfacine is indicated for the treatment of hypertension either alone or in combination with other antihypertensives. Off-label Uses: Attention deficit hyperactivity disorder (ADHD) (Shire has received Complete Response Letter from FDA for Intuniv; marketing approval pending)
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Tourette’s Syndrome (children/adolescents) Dosage and Administration: 1 The recommended initial dose of guanfacine hydrochloride when given in combination with another antihypertensive drug is 1 mg daily given at bedtime to minimize somnolence. If after 3 to 4 weeks of therapy, 1 mg does not give a satisfactory result, a dose of 2 mg may be given.
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  • Spring '16
  • Attention-deficit hyperactivity disorder, Methylphenidate, deficit hyperactivity disorder, attention deficit hyperactivity, Guanfacine

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