TAZTIA XT
Clinical safety rating
cautionComprehensive 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. |
| Molecular Weight | 450.98 |
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 | Diltiazem, the active ingredient in TAZTIA XT, is classified as Pregnancy Category C. Animal studies have shown adverse effects on fetal development, but there are no adequate and well-controlled studies in pregnant women. Limited human data suggest a potential risk of congenital anomalies, particularly cardiovascular defects, with first-trimester exposure. Use only if potential benefit justifies potential risk to the fetus. |
| 2nd trimester | During the second trimester, diltiazem may cause uterine relaxation and potentially delay labor. There is a risk of fetal hypoxia and bradycardia due to maternal hypotension. Monitor fetal heart rate and maternal blood pressure closely if used. |
| 3rd trimester | In the third trimester, diltiazem can inhibit uterine contractions, potentially prolonging labor. It may cross the placenta and cause adverse effects in the neonate, such as hypotension, bradycardia, and hypocalcemia. Avoid use during labor and delivery unless clearly necessary. |
Clinical note
Comprehensive clinical and safety monograph for TAZTIA XT (TAZTIA XT).
| Placental transfer | Diltiazem crosses the placenta in humans. Cord blood concentrations are approximately equal to maternal plasma concentrations, indicating significant placental transfer. |
| Breastfeeding | Diltiazem is excreted into human breast milk in small amounts. The relative infant dose is estimated to be about 1-5% of the maternal weight-adjusted dose. While generally considered compatible with breastfeeding, caution is advised, especially in preterm infants or those with renal/hepatic impairment. Monitor the infant for signs of hypotension, bradycardia, or feeding difficulties. |
| Lactation Rating | L2 (Safer) according to the LactMed classification, but use with caution. |
| 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. |
| 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. |
■ 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 in presence of functioning ventricular pacemaker)Second- or third-degree AV block (except in presence of functioning ventricular pacemaker)Hypotension (systolic < 90 mm Hg)Acute myocardial infarction with pulmonary congestionKnown hypersensitivity to diltiazem or any component of the formulationConcurrent use with rifampin (due to significant reduction in diltiazem exposure)Concurrent use with ivabradine (increased risk of bradycardia and conduction disturbances)
| 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. |
| Food/Dietary | Avoid grapefruit and grapefruit juice as they inhibit CYP3A4 and can increase diltiazem plasma concentrations, elevating risk of bradycardia and hypotension. No other significant food interactions. Administer with or without food. |
| Clinical Pearls | TAZTIA XT is a once-daily extended-release formulation of diltiazem (240 mg, 300 mg, 360 mg). Use for hypertension or chronic stable angina. Doses >360 mg are not recommended. Do not crush or chew; the matrix delivery system can cause bezoars. Avoid use in sick sinus syndrome without a pacemaker, second- or third-degree AV block, or hypotension (SBP <90 mmHg). Monitor for bradycardia and peripheral edema. Abrupt withdrawal may exacerbate angina. Contraindicated with IV beta-blockers or in patients with atrial fibrillation/flutter with accessory bypass tract (e.g., WPW). |
| Patient Advice | Take TAZTIA XT once daily at approximately the same time every day, with or without food. · Swallow the capsule whole; do not crush, chew, or open it. The empty shell may appear in stool. · Avoid grapefruit and grapefruit juice as it can increase diltiazem levels and risk of side effects. · Do not suddenly stop taking this medication without consulting your doctor, as chest pain or heart attack may worsen. · Report symptoms like slow heartbeat, dizziness, fainting, or swelling of the ankles/feet. · Limit alcohol intake as it can increase dizziness and lower blood pressure. · Warn about interactions with beta-blockers, digoxin, statins, and CYP3A4 inhibitors/inducers. |
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