Amantadine excretion

Amantadine crosses the blood-brain barrier and is distributed in saliva, nasal secretions, and breast milk (20). Approximately 90% of the drug is excreted unchanged by the kidney, primarily through glomerular filtration and tubular secretion, and there are no reports of metabolic products. Acidification of urine increases the rate of amantadine excretion. The half-life of the drug is 15 to 20 hours in patients with normal renal function. 

Lactation Amantadine is excreted in breast milk. Use is not recommended in nursing mothers. 

Amantadine (see Chapter 21, Section Ill.b.l) is a tricyclic symmetric adamantanamine. It inhibits the uncoating stage which takes place for binding of the virus to cells, of the influenza-A virus. It is used prophylactically for influenza-A infection, and when given within 24 hours of onset for active influenza-A. It shows good oral absorption and is excreted in the urine with an elimination half-life of about 12 hours. The adverse effects are mainly on the CNS and include insomnia, restlessness, nervousness and depression. 

Memantine is not a major substrate for hepatic cytochrome P450 isoenzymes and has not been shown to significantly inhibit or induce these enzymes. However, memantine is partially excreted by renal tubular secretion. Thus, concomitant use of other medications that use the same renal system (i.e., triampterene, hydrochlorothiazide, digoxin, cimetidine, ranitidine, metformin, and quinidine) may affect plasma levels of both drugs (Namenda 2005). Memantine should not be used in combination with other NMDA receptor antagonists, such as amantadine or dextromethorphan, because these combinations have not been formally studied. The clearance of memantine can be reduced when the urine is alkalinized, such as with the concomitant use of sodium bicarbonate or carbonic anhy-... 

Peak plasma concentrations of amantadine are reached 1-4 hours after an oral dose. The plasma half-life is between 2 and 4 hours, most of the drug being excreted unchanged in the urine. 

Pharmacokinetics Both drugs are well absorbed orally. Amantadine distributes throughout the body and readily penetrates into the central nervous system (CNS), whereas rimantadine does not cross the blood-brain barrier to the same extent. Amantadine is not extensively metabolized. It is excreted into the urine and may accumulate to toxic levels in patients with renal failure. On the other hand, rimantadine is extensively metabolized by the liver. Metabolites and parent drug are eliminated by the kidney. 

AMANTADINE 1. ANTIMALARIALS- quinine 2. ANTIPARKINSON S DRUGS -pramipexole t side-effects 1 renal excretion Monitor closely for confusion, disorientation, headache, dizziness and nausea... 

Medications whose excretion is primarily renal and for which there is evidence of age-related reduction in renal and total body clearance include (but are not limited to) amantadine, aminoglycosides, atenolol, captopril, cimetidine, digoxin, lithium, and vancomycin. Some hepatically metabolized medications can yield active, primarily renally excreted metabolites such as iV-acetylprocainamide, normeperidine, and morphine-6-glucuronide, which can accumulate with advancing age owing to reduced renal function. 

Both drugs have very large volumes of distribution. Nasal secretion and salivary levels of amantadine approximate those found in the serum. Amantadine is excreted in breast milk. Rirrumtadine... 

Amantadine is a primary amine, with a pKa of 10.8, and most of the drug is in the protonated form at physiologic pH. Nevertheless, the drug may enter the brain because of its cage-like structure that not only increases its lipophilicity but also precludes its catabolism by oxidative enzymes metabolism studies have shown that amantadine is excreted in the urine unchanged. 

Uncertain. Amantadine is largely excreted unchanged in the urine and it seems probable that these diuretics reduce the renal clearance. ... 

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