Triamterene

CLINICAL USE

Diuretic (potassium-sparing)

DOSE IN NORMAL RENAL FUNCTION

150–250 mg daily in divided doses; reduce to alternate days after 1 week

PHARMACOKINETICS

Molecular weight : 253

%Protein binding : 60

%Excreted unchanged in urine : 5–10

Volume of distribution (L/kg) : 2.2–3.7

half-life – normal/ESRD (hrs) : 2/10

DOSE IN RENAL IMPAIRMENT

GFR (mL/MIN)

20 to 50 : Dose as in normal renal function

10 to 20 : Avoid. See ‘Other Information’

<10 : Avoid. See ‘Other Information’

DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES

CAPD : Unknown dialysability. Avoid

HD : Unknown dialysability. Avoid

HDF/high flux : Unknown dialysability. Avoid

CAV/VVHD : Unknown dialysability. Avoid

IMPORTANT DRUG INTERACTIONS

Potentially hazardous interactions with other drugs ACE inhibitors and angiotensin-II antagonists: enhanced hypotensive effect (risk of severe hyperkalaemia)

Analgesics: increased risk of nephrotoxicity with NSAIDs; increased risk of hyperkalaemia, especially with indometacin; antagonism of hypotensive effect

Antibacterials: avoid concomitant use with lymecycline

Antidepressants: enhanced hypotensive effect with MAOIs; increased risk of postural hypotension with tricyclics

Antipsychotics: enhanced hypotensive effect with phenothiazines Antihypertensives: enhanced hypotensive effect; increased risk of first dose hypotensive effect of post-synaptic alpha- blockers, e.g. prazosin

Ciclosporin: increased risk of hyperkalaemia

Lithium: reduced excretion of lithium (risk of lithium toxicity)

Potassium salts: increased risk of hyperkalaemia

Tacrolimus: increased risk of hyperkalaemia

ADMINISTRATION

Reconstition

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Route

Oral

Rate of Administration

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Comments

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OTHER INFORMATION

Hyperkalaemia is common when GFR<30 mL/min. May cause acute renal failure Potassium-sparing diuretics are weak diuretics and are ineffective in moderate to severe renal failure .

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