HYDROMOX R
Clinical safety rating: caution
Comprehensive clinical and safety monograph for HYDROMOX R (HYDROMOX R).
Thiazide-like diuretic that inhibits sodium-chloride cotransport in the distal convoluted tubule, increasing excretion of sodium, chloride, and water.
| Metabolism | Primarily hepatically metabolized via cytochrome P450 enzymes (CYP3A4 and others). |
| Excretion | Renal: approximately 70% as unchanged drug; biliary/fecal: approximately 30% as unchanged drug and metabolites. |
| Half-life | Terminal elimination half-life is approximately 2 hours in patients with normal renal function; may be prolonged in renal impairment. |
| Protein binding | Approximately 90% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Approximately 3 L/kg; indicates extensive tissue distribution. |
| Bioavailability | Oral bioavailability is approximately 65-70% due to first-pass metabolism. |
| Onset of Action | Oral: within 2 hours; peak effect at 3-6 hours. |
| Duration of Action | Approximately 12-24 hours; diuresis continues for about 12 hours after oral administration. |
| Molecular Weight | 297.74 Da |
Oral, 50 mg once daily, increased to 100 mg once daily if needed.
| Dosage form | TABLET |
| Renal impairment | GFR 10-50 mL/min: 50 mg every 48 hours; GFR <10 mL/min: not recommended. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: 50 mg every 48 hours; Child-Pugh C: not recommended. |
| Pediatric use | Not established; safety and efficacy not determined. |
| Geriatric use | Initiate at 25 mg once daily; titrate cautiously due to increased sensitivity. |
| 1st trimester | Thiazide diuretics are generally avoided in the first trimester due to potential teratogenic effects and risk of maternal hypovolemia. Limited human data; animal studies have shown fetal abnormalities at high doses. Use only if clearly needed. |
| 2nd trimester | May be used if benefit outweighs risk, but caution is advised due to potential for decreased placental perfusion and electrolyte imbalances. |
| 3rd trimester | Avoid use in third trimester as it may cause fetal or neonatal jaundice, thrombocytopenia, and electrolyte disturbances. Can also interfere with labor. |
Clinical note
Comprehensive clinical and safety monograph for HYDROMOX R (HYDROMOX R).
| Placental transfer | Thiazides cross the placenta. Fetal serum concentrations are similar to maternal levels. Risk of fetal/neonatal adverse effects including electrolyte imbalance and hypoglycemia. |
| Breastfeeding | Hydromox R (hydrochlorothiazide) is excreted into breast milk in small amounts. It may suppress lactation and cause adverse effects in the infant such as electrolyte disturbances. Avoid use or use with caution, monitoring infant for signs of diuresis or electrolyte imbalance. |
■ FDA Black Box Warning
None.
| Serious Effects |
AnuriaHypersensitivity to hydrochlorothiazide or sulfonamide-derived drugsSevere renal impairment (CrCl <30 mL/min)Hepatic coma or pre-comaRefractory hypokalemiaHypercalcemiaSymptomatic hyperuricemia (gout)
| Precautions | May cause hypokalemia, hypomagnesemia, and hyperuricemia; monitor electrolytes and renal function. May precipitate hepatic coma in patients with hepatic cirrhosis. Increased risk of photosensitivity and lupus-like reactions. |
| Food/Dietary | Avoid high-potassium foods (e.g., bananas, oranges, tomatoes) unless monitored; hydrochlorothiazide may cause hypokalemia, but enalapril can cause hyperkalemia. Limit alcohol intake to prevent hypotension. Avoid licorice (glycyrrhizin) which can worsen hypokalemia. Take with food to reduce GI upset. |
Loading safety data…
| Lactation Rating | L3 (Moderately Safe) - Use with caution, weigh risks and benefits. |
| Teratogenic Risk | First trimester: No evidence of major malformations in human studies, but animal studies show fetal toxicity at high doses. Second and third trimesters: Use may cause fetal or neonatal jaundice, thrombocytopenia, and electrolyte disturbances. Avoid use for pregnancy-induced hypertension due to decreased placental perfusion. |
| Fetal Monitoring | Monitor maternal blood pressure, serum electrolytes (especially potassium), blood glucose, and fetal growth. Assess for signs of neonatal jaundice and electrolyte imbalance after delivery. |
| Fertility Effects | No direct evidence of impaired fertility. However, electrolyte disturbances may affect ovulatory function. Use in pregnancy may interfere with maternal fluid balance and placental function. |
| Clinical Pearls | HYDROMOX R (enalapril maleate and hydrochlorothiazide) is a fixed-dose combination for hypertension. Monitor renal function and electrolytes, especially potassium and magnesium, due to dual effect on RAAS and thiazide-induced losses. Enalapril may cause angioedema; discontinue immediately if suspected. Hydrochlorothiazide may exacerbate gout and hypercalcemia. Avoid in pregnancy; warn about risk of fetal harm. |
| Patient Advice | Take exactly as prescribed, usually once daily. · Report any swelling of face, lips, or throat immediately. · Avoid salt substitutes containing potassium unless approved by doctor. · May cause dizziness; avoid driving if affected. · Stay hydrated but do not overhydrate; monitor for signs of dehydration. · Use sun protection; thiazides increase photosensitivity. · Do not stop abruptly without consulting prescriber. |