TAZTIA XT
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TAZTIA XT (TAZTIA XT).
Diltiazem inhibits calcium ion influx across cardiac and vascular smooth muscle cells, resulting in dilation of coronary arteries and peripheral arterioles, and reduction of myocardial contractility and heart rate.
| Metabolism | Hepatic via CYP3A4; active metabolite (desacetyldiltiazem). |
| Excretion | Renal (approximately 60% as unchanged drug and metabolites, primarily via glomerular filtration and tubular secretion), biliary/fecal (approximately 30-35%) |
| Half-life | 3-5 hours (immediate-release) for diltiazem; after TAZTIA XT extended-release, effective half-life is approximately 7-9 hours due to prolonged absorption. Clinical context: steady state achieved in 3-5 days. |
| Protein binding | 70-80% primarily to albumin; also to alpha-1-acid glycoprotein |
| Volume of Distribution | 3.1-5.3 L/kg (central compartment); large Vd indicates extensive tissue distribution, consistent with high lipophilicity and cardiac/vascular tissue binding. |
| Bioavailability | Oral (extended-release): approximately 35-60% due to extensive first-pass hepatic metabolism (cytochrome P450 3A4) with significant interindividual variability. Food may increase bioavailability by up to 20%. |
| Onset of Action | Oral (extended-release): 2-3 hours to measurable antihypertensive effect; maximal effect at steady state after 2 weeks of dosing. |
| Duration of Action | Oral (extended-release): 24 hours (once-daily dosing maintains blood pressure control over 24-hour interval). Clinical note: Diltiazem has a narrower therapeutic index; duration may be shorter in patients with hepatic impairment. |
Oral, 120 mg or 180 mg once daily. For hypertension, initiate at 120 mg once daily; for angina, initiate at 180 mg once daily. Maximum dose: 360 mg once daily.
| Dosage form | CAPSULE, EXTENDED RELEASE |
| Renal impairment | No specific dose adjustment recommended for mild to moderate renal impairment. Use caution in severe renal impairment (CrCl <30 mL/min); consider starting at lower dose and titrate slowly. |
| Liver impairment | Child-Pugh Class A or B: No specific adjustment, but use caution. Child-Pugh Class C: Contraindicated. |
| Pediatric use | Safety and efficacy not established; no pediatric dosing guidelines available. |
| Geriatric use | Start at lower end of dosing range (120 mg once daily) due to increased systemic exposure; titrate slowly based on response and tolerability. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for TAZTIA XT (TAZTIA XT).
| Breastfeeding | Diltiazem is excreted into breast milk at low concentrations. A study reported milk-to-plasma (M/P) ratio of approximately 0.8-1.0. Estimated infant dose is <1% of maternal weight-adjusted dose, considered clinically insignificant. However, due to potential for adverse effects (hypotension, bradycardia) in neonates, caution advised. American Academy of Pediatrics considers diltiazem compatible with breastfeeding. Monitor infant for signs of bradycardia or hypotension. |
| Teratogenic Risk | TAZTIA XT (diltiazem) is classified as FDA Pregnancy Category C. In first trimester, animal studies have shown embryofetal toxicity (skeletal abnormalities, fetal mortality) at doses ≥5 times maximum human dose. No adequate human studies in pregnant women; potential risk cannot be ruled out. In second and third trimesters, use may cause uteroplacental hypoperfusion due to maternal hypotension, potentially leading to fetal hypoxia and growth restriction. Case reports associate with preterm labor and low birth weight. Avoid use during pregnancy unless benefit outweighs risk. |
■ FDA Black Box Warning
No FDA boxed warning specific to TAZTIA XT; however, the drug class (calcium channel blockers) may have warnings for increased risk of cardiovascular events in certain populations.
| Serious Effects |
["Sick sinus syndrome (except with functioning pacemaker)","Second- or third-degree AV block (except with pacemaker)","Hypotension (systolic <90 mmHg)","Acute myocardial infarction or pulmonary congestion","Known hypersensitivity to diltiazem","Concurrent use with ivabradine"]
| Precautions | ["Heart failure: May worsen symptoms due to negative inotropic effects.","Bradycardia and heart block: Risk especially in elderly or with other AV nodal blockers.","Hypotension: Especially with rapid dose escalation.","Abrupt withdrawal: May cause rebound angina or hypertension.","Hepatic impairment: Reduced metabolism may require dose adjustment.","Concomitant use with beta-blockers: Increased risk of bradycardia and heart block."] |
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| Fetal Monitoring | Maternal: Monitor blood pressure and heart rate frequently, especially during dose titration. Assess for signs of hypotension, bradycardia, and peripheral edema. Monitor liver function tests (LFTs) and renal function periodically. Fetal: Ultrasound for growth assessment and amniotic fluid volume if used in second/third trimester. Fetal heart rate monitoring during labor if drug administered near term. Consider nonstress test or biophysical profile in third trimester if concerns about fetal well-being. |
| Fertility Effects | No specific human studies on fertility. Animal studies: In rats, diltiazem at oral doses up to 100 mg/kg/day (approximately 6 times maximum human dose) showed no impairment of fertility. However, in vitro studies suggest calcium channel blockers may inhibit sperm motility and acrosome reaction. Clinical significance unknown. Use with caution in patients attempting conception. |