Minoxidil excretion

Lactation Minoxidil is excreted in breast milk do not nurse while taking minoxidil. Children Use in children is limited, particularly in infants. The recommendations under Administration and Dosage are only a rough guide careful titration is essential. 

ABSORPTION, METABOLISM, AND EXCRETION Minoxidil is well absorbed from the GI tract. Although peak concentrations of minoxidil in blood occur 1 hour after oral administration, the maximal hypotensive effect of the dmg occurs later, possibly because formation of the active metabolite is delayed. About 20% of the absorbed drug is excreted unchanged in the urine the main route of elimination is by hepatic metabolism. The major metabolite of minoxidil is the glucuronide conjugate at the /V-oxide position. This metabolite is less active than minoxidil but has a long tj. Minoxidil has a tj in plasma of 3 hours, but its duration of action is 24 hours or longer. 

Minoxidil is absorbed from the Gl tract and is metabolized to its active sulfate metabolite. Plasma concentrations for minoxidil sulfate peak within 1 hour and then decline rapidly. Following an oral dose of minoxidil, its hypotensive effect begins in 30 minutes, is maximal in 2 to 8 hours, and persists for approximately 2 to 5 days. The delayed onset of the hypotensive effect for minoxidil is attributed to its metabolism to its active metabolite. The drug is not bound to plasma proteins. The major metabolite for minoxidil is its N-O-glucuronide, which unlike the sulfate metabolite is inactive as a hypotensive agent. Approximately 10 to 20% of an oral dose of minoxidil is metabolized to its active metabolite, minoxidil O-sulfate, and approximately 20% of minoxidil is excreted unchanged. 

Sulfonation is generally a detoxification pathway whereby the conjugated product has greater water solubility and is therefore excreted more readily from the body. However, several chemicals have been shown to form mutagenic and carcinogenic reactive electrophiles upon sulfonation (Glatt, 2000). Additionally, it is the sulfonated forms of minoxidil and cholecystokinin that elicit biologic activity (Weinshilboum et al., 1997). 

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