Adult: Each tab/cap contains triamterene 37.5 mg and hydrochlorothiazide 25 mg: 1-2 tab/cap once daily. Each tab contains triamterene 50 mg and hydrochlorothiazide 25 mg: Initially, 1 tab daily after the morning meal, adjust thereafter according to response. Max: 4 tab daily. Each tab/cap contains triamterene 75 mg and hydrochlorothiazide 50 mg: 1 tab/cap daily.
Oral Oedema
Adult: Each tab/cap contains triamterene 37.5 mg and hydrochlorothiazide 25 mg: 1-2 tab/cap once daily. Each tab contains triamterene 50 mg and hydrochlorothiazide 25 mg: Initially, 1 tab bid. Maintenance: 1 tab daily or 2 tab on alternate days. Max: 4 tab daily. Each tab/cap contains triamterene 75 mg and hydrochlorothiazide 50 mg: 1 tab/cap daily.
Administration
Should be taken with food.
Contraindications
Hyperkalaemia (≥5.5 mEq/L), hypercalcaemia, diabetic ketoacidosis, Addison’s disease, progressive renal failure, increasing hepatic dysfunction. Concomitant use w/ K supplements, other K-conserving drugs, including ACE inhibitors.
Special Precautions
Patients w/ prediabetes or DM, diabetic nephropathy, predisposition to gout, history of renal lithiasis. Hepatic or renal impairment. Pregnancy and lactation.
This drug may cause a blue fluorescence of the urine under certain light conditions.
Monitoring Parameters
Monitor BUN, BP, serum K levels and other electrolytes, creatinine, LFTs, signs of hyperkalaemia.
Overdosage
Symptoms: Electrolyte imbalance, nausea, vomiting, weakness, polyuria, lassitude, fever, flushed face, hyperactive deep tendon reflexes, hypotension, cardiac arrhythmias. Management: Induce immediate evacuation through emesis or gastric lavage. Pressor agents e.g. norepinephrine may be given in case of hypotension.
Drug Interactions
May reduce the renal clearance of lithium. May antagonise diuretic effect w/ NSAIDs, corticosteroids, oestrogens, combined OCs. Enhanced effect w/ other hypotensive agents, baclofen, tizanidine. May decrease arterial responsiveness to norepinephrine. Increases responsiveness to tubocurarine. Risk of acute renal failure w/ indometacin. Increased risk of hyperkalaemia w/ reboxetine, tacrolimus. Increased risk of ototoxicity and nephrotoxicity w/ platinum compounds (e.g. cisplatin). Potentially Fatal: Increased risk of hyperkalaemia w/ K supplements, other K-conserving drugs, including ACE inhibitors.
Lab Interference
Interferes w/ some thyroid and parathyroid function tests, bioassay of folic acid and measurement of quinidine.
Action
Description: Triamterene directly inhibits the exchange of Na for K and hydrogen in the distal renal tubule. Hydrochlorothiazide increases the excretion of Na and Cl ions, and consequently of water, by reducing electrolyte reabsorption from the renal tubules. Onset: W/in 1 hr. Pharmacokinetics: Absorption: Incompletely but fairly rapidly absorbed from the GI tract. Triamterene: Bioavailability: Approx 50%. Time to peak plasma concentration: W/in 1 hr. Hydrochlorothiazide: Bioavailability: Approx 65-70%. Time to peak plasma concentration: Approx 2 hr. Distribution: Triamterene: Plasma protein binding: Approx 67%. Hydrochlorothiazide: Crosses the placenta and enters breast milk. Metabolism: Triamterene: Metabolised to 6-p-hydroxytriamterene and its sulfate conjugate. Excretion: Triamterene: Via urine (10-88%); bile (variable amounts). Plasma half-life: Approx 2 hr. Hydrochlorothiazide: Via urine as unchanged drug. Elimination half-life: Approx 3-6 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)
Hydrochlorothiazide Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 3639, Hydrochlorothiazide. https://pubchem.ncbi.nlm.nih.gov/compound/Hydrochlorothiazide. Accessed Feb. 23, 2023.
C03EA01 - hydrochlorothiazide and potassium-sparing agents ; Belongs to the class of low-ceiling diuretics in combination with potassium-sparing agents. Used as diuretics.
References
Anon. Hydrochlorothiazide and Triamterene. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 10/03/2016.Buckingham R (ed). Hydrochlorothiazide. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 10/03/2016.Buckingham R (ed). Triamterene. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 10/03/2016.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 10/03/2016.Triamterene and Hydrochlorothiazide Tablet (Actavis Pharma, Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 10/03/2016.
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