what a flare

mrsD · 02-27-2012, 02:17 PM

@fmichael:

I found your doctor's statement that Namenda would be increased by the quinidine in the Nuedexta, strange. So I looked it up:

This combo did not appear on the standard drugchecker at drugs.com to have interactions. This monograph explains why:

Quote:

Metabolism and Elimination

Memantine undergoes partial hepatic metabolism. About 48% of administered drug is excreted unchanged in urine; the remainder is converted primarily to three polar metabolites which possess minimal NMDA receptor antagonistic activity: the N-glucuronide conjugate, 6-hydroxy memantine, and 1-nitroso-deaminated memantine. A total of 74% of the administered dose is excreted as the sum of the parent drug and the N-glucuronide conjugate. The hepatic microsomal CYP450 enzyme system does not play a significant role in the metabolism of memantine. Memantine has a terminal elimination half-life of about 60-80 hours. Renal clearance involves active tubular secretion moderated by pH dependent tubular reabsorption....Inhibitors of Microsomal Enzymes: Since memantine undergoes minimal metabolism, with the majority of the dose excreted unchanged in urine, an interaction between memantine and drugs that are inhibitors of CYP450 enzymes is unlikely. Coadministration of Namenda with the AChE inhibitor donepezil HCl does not affect the pharmacokinetics of either compound.

from http://www.drugs.com/pro/namenda.html
In fact even moderate hepatic impairment does not appreciably affect Namenda metabolism. The most significant factor is renal damage and poor clearance there.
In fact if the urine pH increases...the drug may not be cleared well:

Quote:

Drugs that make the urine alkaline: The clearance of memantine was reduced by about 80% under alkaline urine conditions at pH 8. Therefore, alterations of urine pH towards the alkaline state may lead to an accumulation of the drug with a possible increase in adverse effects. Drugs that alkalinize the urine (e.g. carbonic anhydrase inhibitors, sodium bicarbonate) would be expected to reduce renal elimination of memantine.

Also quinidine is not a "tricyclic antidepressant"....it is a heart drug for arrhythmias:
http://en.wikipedia.org/wiki/Quinidine

This is a list from drugs.com of drugs that interact with quinidine considered MAJOR:
http://www.drugs.com/drug-interactio...&generic_only=

This list includes major and moderate interactions:
http://www.drugs.com/drug-interactio....html?filter=2

The drugchecker at www.drugs.com is very good. I suggest you check all your medications against quinidine just for safety's sake.

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