Adult: 150-250 mg bid, after breakfast and lunch. Maintenance: Doses may be given on alternate days. Max: 300 mg daily.
Oral Hypertension
Adult: In combination w/ other diuretics (e.g. hydrochlorothiazide): Initially, 50 mg daily.
Renal Impairment
Severe: Contraindicated.
Hepatic Impairment
Severe: Contraindicated.
Administration
Should be taken with food.
Contraindications
Pre-existing or drug-induced hyperkalaemia, anuria, Addison's disease. Severe renal and hepatic impairment. Concomitant use w/ other K-sparing agents, K supplements.
Special Precautions
Patient w/ DM, hyperuricaemia or gout, history of renal calculi. Renal and hepatic impairment. Pregnancy and lactation.
Symptoms: Electrolyte imbalance esp hyperkalaemia, GI disturbances (e.g. nausea, vomiting), weakness, hypotension. Management: Induced gastric lavage or emesis. Admin pressor agents (e.g. norepinephrine) for severe hypotension. May perform dialysis.
Drug Interactions
May reduce antihypertensive effect w/ NSAIDs. May increase hyperkalaemic effect of ACE inhibitors. May increase risk of lithium toxicity. Increased risk of postural hypotension w/ TCAs. Increased risk of hyponatraemia w/ carbamazepine. May increase nephrotoxic effect w/ indometacin. Potentially Fatal: May increase risk of hyperkalaemia w/ other K-sparing agents, K supplements.
Lab Interference
May interfere w/ the methods of enzyme assay that depend on fluorometry (e.g. determination of lactic dehydrogenase activity). Interferes w/ fluorometric assay of quinidine and bioassay of folic acid.
Action
Description: Triamterene is a weak K-sparing diuretic which appears to act mainly on the distal renal tubules. It increases the excretion of Na, Mg, Ca, bicarbonate and decreases K excretion. It adds to the natriuretic but reduces the kaliuretic effects of other diuretics. Onset: Diuresis: 2-4 hr. Duration: Diuresis: 7-9 hr. Pharmacokinetics: Absorption: Variably but fairly rapidly absorbed from the GI tract. Bioavailability: Approx 50%. Time to peak plasma concentration: 3 hr. Distribution: Crosses the placenta; enters breast milk. Plasma protein binding: Approx 60%. Metabolism: Extensively metabolised by CYP1A2 isoenzyme to the sulfate conjugate of hydroxytriamterene. Excretion: Via urine (21% to <50%, mainly as metabolites). Plasma half-life: Approx 2 hr.
Chemical Structure
Triamterene Source: National Center for Biotechnology Information. PubChem Database. Triamterene, CID=5546, https://pubchem.ncbi.nlm.nih.gov/compound/Triamterene (accessed on Jan. 23, 2020)
C03DB02 - triamterene ; Belongs to the class of other potassium-sparing agents. Used as diuretics.
References
Anon. Triamterene. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 12/11/2014.Buckingham R (ed). Triamterene. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 12/11/2014.Dyrenium Capsule (WellSpring Pharmaceutical Corporation). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 12/11/2014.Joint Formulary Committee. Triamterene. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 12/11/2014.McEvoy GK, Snow EK, Miller J et al (eds). Triamterene. AHFS Drug Information (AHFS DI) [online]. American Society of Health-System Pharmacists (ASHP). https://www.medicinescomplete.com. Accessed 12/11/2014.
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