Generic Name

Triamterene

Mechanism

Triamterene competitively inhibits the epithelial sodium channel (ENaC) in the late distal tubule and collecting duct.
• ↓ Na⁺ reabsorption → ↑ natriuresis and diuresis.
• ↓ K⁺ excretion → potassium sparing effect, decreasing the risk of hypokalemia caused by other diuretics.

Pharmacokinetics

• Absorption: Oral bioavailability ~85 %; peak plasma concentrations in 1–2 h.
• Distribution: Widely distributed; binds weakly to plasma proteins (<5 %).
• Metabolism: Minimal hepatic metabolism; primarily excreted unchanged.
• Elimination: Renal excretion ~85 % unchanged; half‑life ≈ 5–6 h (may prolong to 8–10 h in renal impairment).
• Special considerations: Dose adjustment in severe renal dysfunction; not recommended in severe hepatic disease.

Indications

• Hypertension (when combined with a loop or thiazide diuretic).
• Edema secondary to heart failure, liver cirrhosis, or nephrotic syndrome (as adjunct therapy).
• Prevention of diuretic‑induced hypokalemia when used with loop or thiazide agents.

Contraindications

• Contraindicated:
• Severe renal impairment (CrCl < 30 mL/min).
• End‑stage renal disease on dialysis.
• Hyperkalemia at baseline.
• Warnings:
• Monitoring of serum potassium and creatinine recommended within the first week of therapy.
• Susceptible to gout flare‑ups; avoid in patients with active gout.
• Potential interactions: NSAIDs may reduce excretion, increasing potassium retention.

Dosing

• Administration with food to enhance tolerability.
• Adjust dose in renal impairment: hold if CrCl < 30 mL/min; re‑initiate lower dose once renal function improves.
• Combination dosing: Often prescribed as a fixed‑dose combination with hydrochlorothiazide (HCTZ) in a single tablet for patient convenience.

Adverse Effects

Common (≤10 %)
• Hyperkalemia (most significant).
• Elevated serum creatinine.
• Diarrhea, headache.
• Rash (rare, may indicate hypersensitivity).

Serious (≤1 %)
• Severe hyperkalemia → arrhythmias, muscle weakness.
• Renal failure (especially when combined with ACE inhibitors/ARBs).
• Gout flare (uric acid ↑).
• Severe allergic reactions (anaphylaxis).

Monitoring

• Serum electrolytes: potassium, sodium, chloride, bicarbonate—baseline, 2–3 days, then weekly for 4 weeks, then monthly.
• Renal function: serum creatinine, eGFR at baseline and then periodically.
• Serum uric acid in patients with history of gout.
• Cardiac monitoring: Assess for arrhythmias if potassium > 5.5 mEq/L.

Clinical Pearls

• PEARL #1 – Fixed‑dose pair benefits: The HCTZ/triamterene combo simplifies dosing, improves adherence, and reduces the overall pill burden.
• PEARL #2 – Hyperkalemia vigilance: Even mild rises in potassium can trigger serious arrhythmias; always check electrolytes before starting or switching to this agent.
• PEARL #3 – Gout prophylaxis tip: For patients prone to gout, consider co‑prescribing allopurinol or febuxostat when initiating triamterene therapy.
• PEARL #4 – Renal function as the gatekeeper: In CKD stage 3–4 patients, limit the dose to 125 mg or discontinue if CrCl drops below 30 mL/min.
• PEARL #5 – Dosing in pregnancy: Category C; use only when benefits outweigh risks—prefer low‑dose formulations and monitor potassium closely.

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• *This drug card summarises key pharmacological aspects of Triamterene for quick reference by medical students and clinicians, balanced with safety considerations and evidence‑based monitoring.*