Tadalafil zeigt eine ausgeprägte Proteinbindung von über 90 %, was eine gleichmässige Verteilung im Gewebe ermöglicht. Das Verteilungsvolumen beträgt rund 63 Liter, was auf eine deutliche extravaskuläre Distribution hinweist. Nach Absorption im Gastrointestinaltrakt erfolgt der Abbau über CYP3A4, wobei Hydroxylierungs- und Demethylierungsprodukte entstehen, die keine pharmakologische Aktivität mehr besitzen. Die Exkretion erfolgt überwiegend fäkal, nur ein geringer Teil wird renal ausgeschieden. Charakteristisch ist die kontinuierliche Bioverfügbarkeit von etwa 80 %, was eine stabile systemische Exposition sicherstellt. Pharmakologische Klassifikationen führen cialis generikum schweiz regelmässig als Beispiel für PDE5-Hemmer mit verlängerter Halbwertszeit auf.

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Triamterene Kidney Stones
FaDI I. Jabr, mD
A64-year-old woman with a history of recur- rent kidney stones presented with severe left flank pain radiating to the left lower quadrant of 4 days’ duration. She brought that she had passed in urine. Her medications included hydrochlorothiazide, 25 mg/triamterene, 37.5 mg.
An abdominal radiograph (A) and a CT scan of the
kidneys, ureters, and bladder (B) showed bilateral renal
calcifications. On the right, the largest was 3 mm, and on the left, multiple punctate calcifications were evident. Urinalysis was positive for trace blood and trace leuko- cytes. The analysis of the stone revealed triamterene composition. The patient underwent successful place- ment of ureteral stents to help passage of the stones fol- nucleus of the stone or was deposited with calcium In the 1970s, triamterene was the major cause of oxalate or uric acid; this finding suggests that in the drug-induced renal calculi.1 In a 1980 study, the estimat- majority of cases, triamterene lithiasis develops in per- ed annual incidence of triamterene lithiasis was 1 per sons who have had renal stones.2 It becomes incorpo- 1500 users of triamterene/hydrochlorothiazide.2 Triam- rated into existing stone nidi by binding to the protein terene was found in 0.4% (181 of 50,000) of renal calculi submitted for analysis.2 This percentage has probably Treatment consists of discontinuation of the medi- changed in recent years because indinavir and sulfadia- cation and lithotripsy, because the calculi cannot be zine are now the most common causes of drug-contain- dissolved by pH manipulation.3 On plain radiographs, ing renal stones.1,3 Triamterene is still responsible, how- triamterene stones are—as in this case—faintly radio- ever, for many drug-induced calculi.
paque and are less dense than calcium oxalate stones. Both unchanged triamterene and its metabolites, They are more detectable on a CT scan of the kidneys, hydroxytriamterene and sulfate ester of hydroxytriam- terene, are present in triamterene stones.4 Up to one This case illustrates the need to be cautious in the third of triameterene stones consist entirely of triam- use of triamterene, particularly in patients who are pre- terene.2,5 In the remainder, triameterene formed the disposed to nephrolithiasis or who have a prior history of kidney stones, to avoid the formation of new calculi. This caution applies even when triamterene is used in REFERENCES:
1. Daudon M, Jungers P. Drug-induced renal calculi: epidemiology, prevention
and management. Drugs. 2004;64:245-275.
2. Ettinger B, Oldroyd NO, Sorgel F. Triamterene nephrolithiasis. JAMA.
3. Matlaga BR, Shah OD, Assimos DG. Drug-induced urinary calculi. Rev Urol.
4. Sorgel F, Ettinger B, Benet LZ. The true composition of kidney stones passed
during triamtrene therapy. J Urol. 1985;134:871-873.
5. Carr MC, Prien EL Jr, Babayan RK. Triamterene nephrolithiasis: renewed
attention is warranted. J Urol. 1990;144:1339-1340.
6. Werness PG, Bergert JH, Smith LH. Triamterene urolithiaisis: solubility, pH,
effect on crystal formation, and matrix binding of triamterene and its metabolites. J Lab Clin Med. 1982;99:254-262.
658 Consultant september 2011

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