Triamterene/HydrochlorothiazideTriamterene / Hydrochlorothiazide

About Triamterene/Hydrochlorothiazide

Hydrochlorothiazide, a thiazide diuretic, makes the kidneys pass salt and water but also potassium; triamterene, a potassium-sparing diuretic, offsets that potassium loss. The label covers high blood pressure or edema in people who develop low potassium on hydrochlorothiazide alone, and people who need a thiazide but in whom low potassium cannot be risked. It is not for starting treatment, except in people who cannot risk low potassium, and it can be used with other blood pressure medicines such as beta blockers. The 37.5/25 mg capsules are taken as one or two once a day; the 37.5/25 mg tablets as one or two a day in a single dose; the 75/50 mg tablet as one a day. Safety and effectiveness in children have not been established.

The boxed warning is high potassium: levels of 5.5 mEq per liter or more can occur with any potassium-sparing combination, more often with kidney impairment, diabetes, older age or severe illness, and because untreated high potassium can be fatal, potassium is checked often, especially at the start, after dose changes and during illness that affects the kidneys. It must not be taken when potassium is already high; with spironolactone, amiloride or other triamterene products; with potassium salt substitutes or potassium supplements (the capsule label allows supplements only for severe low potassium, with careful monitoring, and the tablet label also rules out potassium-enriched diets); with absent urine output or significant kidney disease; or with an allergy to triamterene, hydrochlorothiazide or other sulfonamide-derived drugs. Reported side effects include muscle cramps, weakness, tiredness, dizziness, headache, dry mouth and nausea.

Triamterene has been found in kidney stones, so a history of stones calls for caution, and the tablet label adds that it is a weak folic acid antagonist, a concern when folate stores are low. The combination can also raise uric acid and bring on gout, change blood sugar control and activate lupus, and with liver disease small shifts in fluid and salts can bring on hepatic coma. The hydrochlorothiazide can cause sudden nearsightedness and angle-closure glaucoma, which needs urgent care, and raises the risk of non-melanoma skin cancer, so the label advises sun protection and regular skin checks. Safe use in pregnancy has not been established, and the labels say to stop breastfeeding if the drug is essential. The capsule and the tablet are different products: the tablet label says patients changed to it from less bioavailable formulations should be monitored clinically and for potassium after the change.

Taking Triamterene/Hydrochlorothiazide

How to take it

As prescribed, after a meal to avoid stomach upset; a once-daily dose is taken in the morning so that extra urination does not disturb sleep. Keep appointments for potassium and other blood tests.

If you miss a dose

Take it as soon as you remember, unless it is almost time for the next dose; then skip the missed dose and carry on as usual. Do not take a double dose.

Storage

At room temperature in a tightly closed container, protected from light and moisture, out of reach of children.

Interactions to know about

Potassium supplements, potassium salt substitutes, low-salt milk, spironolactone and amiloride are avoided; ACE inhibitors raise the risk of high potassium. Acute kidney failure has been reported with indomethacin, so NSAIDs are used with caution; lithium is generally not given with diuretics, and chlorpropamide may drop sodium too low. Protect your skin from the sun.

This summarizes the official prescribing information. Your prescriber’s and pharmacist’s instructions, and the leaflet that comes with your medicine, take priority.

Why the cash price for Triamterene/Hydrochlorothiazide differs from pharmacy to pharmacy

Both forms are old generics that cost pharmacies little, so a quote is mostly the dispensing fee and markup, and whether the drug is on a pharmacy’s flat-price generic list varies. A prescription that blocks substitution limits the pharmacy to the product named.

The capsule and the tablet are different products, each with its own generic makers, so one form can be quoted lower than the other at the same pharmacy. A change from one to the other is the prescriber’s decision: the tablet label calls for clinical and potassium monitoring after a change to it from a less bioavailable formulation.

Ways to pay less for Triamterene/Hydrochlorothiazide without insurance

• Ask for generic substitution, and ask whether the drug is on the pharmacy’s flat-price generic list.
• Ask for a ninety-day supply once your dose and potassium are stable.
• If you take two 37.5/25 mg tablets a day, ask the prescriber whether one 75/50 mg tablet, the same total dose, would suit you.
• If one form is quoted high, ask the prescriber whether the other form would suit you, and when your potassium should be checked after a change.
• Upload the prescription to Script Unlock so licensed pharmacies can quote their cash price. You pay the pharmacy directly.

Questions to ask your pharmacist about Triamterene/Hydrochlorothiazide

1. 1.When will my potassium and kidney function be checked?
2. 2.Which salt substitutes, potassium supplements and other products should I avoid?
3. 3.Is my prescription for the capsule or the tablet, and does it matter which?
4. 4.Is it safe with my lithium, ACE inhibitor or anti-inflammatory painkiller?

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