Guanfacine HCl is absorbed orally, with a bioavailability of 80%. It is taken once daily, usually in the morning, but it should not be taken with high-fat meals. The drug is approximately 70% bound to plasma proteins, and it is widely distributed throughout the body, with a volume of distribution (Vd) of 6.3 L/kg (276–347 L). Fifty percent of the drug is metabolized in the liver, primarily to the glucuronide and sulfate of 3-hydroxyguanfacine, oxidized mercapturic acid derivatives, and other minor metabolites.
Guanfacine HCl is metabolized primarily by cytochrome P-450 (CYP) 3A4. It is a substrate of CYP 3A4 and CYP 3A5, and exposure is affected by inducers and inhibitors of these enzymes.
Renal excretion is 50%, and the elimination half-life is 17 hours (range, 10–30 hours). Patients on dialysis can be given their customary doses of guanfacine HCl because the drug is poorly dialyzed.
This product has an affinity that is 15 to 20 times higher for the alpha2A receptor subtype than for the alpha2B or alpha2C subtypes. As an antihypertensive agent, guanfacine stimulates alpha2A-adrenergic receptors, thereby reducing sympathetic nerve impulses from the vasomotor center to the heart and blood vessels. The result is a decrease in peripheral vascular resistance and a reduced heart rate.
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flmarcus: I'm 57 and have been on Adderall for over 15 years. Can't seem to function without it. Is that normal for most of us ?
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