TELMISARTAN AND HYDROCHLOROTHIAZIDE
Clinical safety rating: avoid
NSAIDs may diminish the antihypertensive effect Lithium levels may be increased Use in pregnancy can cause injury and death to the developing fetus.
Telmisartan is an angiotensin II receptor blocker (ARB) that selectively inhibits the binding of angiotensin II to the AT1 receptor, leading to vasodilation and reduced aldosterone secretion. Hydrochlorothiazide is a thiazide diuretic that inhibits the sodium-chloride symporter in the distal convoluted tubule, increasing excretion of sodium and water.
| Metabolism | Telmisartan is primarily metabolized by glucuronidation via UGT1A3 and UGT2B7; minimal CYP450 metabolism. Hydrochlorothiazide is not metabolized and is excreted unchanged in urine. |
| Excretion | Telmisartan: >99% biliary-fecal as unchanged drug, <2% renal. Hydrochlorothiazide: ≥95% renal as unchanged drug; minimal biliary. |
| Half-life | Telmisartan: 24 hours (terminal); supports once-daily dosing with ~3-5 days to steady state. Hydrochlorothiazide: 6-15 hours (mean 10h); prolonged in renal impairment. |
| Protein binding | Telmisartan: >99.5% (primarily albumin and α1-acid glycoprotein). Hydrochlorothiazide: 40-68% (primarily albumin). |
| Volume of Distribution | Telmisartan: 500 L (approx 7 L/kg for 70 kg; extensive tissue binding). Hydrochlorothiazide: 0.83 L/kg (distributes into extracellular fluid; crosses placenta but minimal CNS entry). |
| Bioavailability | Telmisartan: 42-58% (oral); high-fat meal reduces AUC by 6%. Hydrochlorothiazide: 65-72% (oral); food may increase absorption. |
| Onset of Action | Telmisartan: 30-60 minutes (oral); peak effect 3-6 hours. Hydrochlorothiazide: 2 hours (oral); peak effect 4 hours. |
| Duration of Action | Telmisartan: 24 hours (antihypertensive); enables once-daily dosing. Hydrochlorothiazide: 6-12 hours (diuresis); antihypertensive effect persists >24 hours. |
Oral, one tablet once daily. Initial: Telmisartan 40 mg/HCTZ 12.5 mg; titrate to max 80 mg/25 mg once daily.
| Dosage form | TABLET |
| Renal impairment | GFR ≥30 mL/min: No adjustment. GFR 15-29 mL/min: Not recommended (loop diuretics preferred). GFR <15 mL/min: Contraindicated. |
| Liver impairment | Child-Pugh A: No adjustment for telmisartan up to 40 mg; maximum HCTZ 25 mg. Child-Pugh B: Telmisartan 20 mg max; HCTZ 12.5 mg max. Child-Pugh C: Contraindicated. |
| Pediatric use | Safety and efficacy not established. Use not recommended. |
| Geriatric use | Start at lowest dose (40/12.5 mg). Monitor renal function and electrolytes closely. Titrate slowly. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
NSAIDs may diminish the antihypertensive effect Lithium levels may be increased Use in pregnancy can cause injury and death to the developing fetus.
| FDA category | Contraindicated |
| Breastfeeding | Telmisartan is excreted in human milk in low amounts; M/P ratio not reported. Hydrochlorothiazide is excreted in breast milk in low concentrations (M/P ratio approximately 0.2-0.7). Due to potential for neonatal electrolyte disturbances and hypotension, caution is advised; alternative agents preferred. |
| Teratogenic Risk |
■ FDA Black Box Warning
Fetal toxicity: Drugs acting directly on the renin-angiotensin system can cause injury and death to the developing fetus. Discontinue as soon as possible once pregnancy is detected.
| Common Effects | Hyperkalemia |
| Serious Effects |
["Anuria","Hypersensitivity to telmisartan, hydrochlorothiazide, or sulfonamide-derived drugs","Concomitant use with aliskiren in patients with diabetes"]
| Precautions | ["Avoid use in pregnancy","Hypotension in volume-depleted patients","Monitor renal function and serum electrolytes","Worsening of renal function","Acute myopia and secondary angle-closure glaucoma (hydrochlorothiazide)"] |
Loading safety data…
| Telmisartan is an angiotensin II receptor blocker (ARB); use during second and third trimesters is associated with oligohydramnios, fetal renal dysfunction, skull hypoplasia, and death. First trimester exposure may increase risk of congenital malformations, though data are limited. Hydrochlorothiazide (HCTZ) does not appear to be major teratogen but can cause electrolyte disturbances and decreased placental perfusion. Overall, combination is contraindicated in pregnancy, especially after 20 weeks gestation. |
| Fetal Monitoring | Monitor maternal blood pressure, serum creatinine, potassium, and electrolytes. Fetal ultrasound to assess amniotic fluid volume and fetal growth if exposure occurs after 20 weeks. Monitor for signs of fetal hypotension or renal dysfunction. |
| Fertility Effects | No specific human studies; animal studies suggest telmisartan may alter renin-angiotensin system in fetal kidney development. No direct evidence of impaired fertility; HCTZ may cause maternal electrolyte imbalances that could theoretically affect ovulation, but data lacking. |