CARTIA XT
Clinical safety rating
cautionComprehensive clinical and safety monograph for CARTIA XT (CARTIA XT).
Diltiazem, a benzothiazepine calcium channel blocker, inhibits calcium ion influx across cardiac and vascular smooth muscle cells during depolarization, leading to vasodilation and reduced myocardial contractility and conduction velocity, particularly at the AV node.
| Metabolism | Primarily hepatic via CYP3A4; extensive first-pass metabolism. Metabolites include desacetyldiltiazem (active, 25-50% potency). |
| Excretion | Renal (biliary/fecal minimal). 70-80% excreted as inactive metabolites in urine; 15% unchanged. |
| Half-life | Terminal half-life 3-4.5 hours; prolonged in hepatic impairment (up to 15 hours) or with cimetidine. |
| Protein binding | 40-50% bound to albumin. |
| Volume of Distribution | Vd 5-10 L/kg; reflects extensive tissue distribution (highly lipophilic). |
| Bioavailability | IR: 30-40% (first-pass metabolism); ER (CARTIA XT): 30-40% relative to IR. |
| Onset of Action | IR: 30-60 min; ER (CARTIA XT): 2-4 hours. |
| Duration of Action | IR: 4-6 hours; ER: 24 hours (once-daily dosing). |
| Molecular Weight | 414.52 |
Diltiazem hydrochloride extended-release capsules (CARTIA XT) are administered orally. For hypertension and angina, the typical adult dose is 180–360 mg once daily, initially 180 mg once daily, titrated to response.
| Dosage form | CAPSULE, EXTENDED RELEASE |
| Renal impairment | No specific dose adjustment is required for renal impairment. However, use with caution in patients with severe renal impairment (CrCl <30 mL/min) and monitor heart rate and blood pressure. |
| Liver impairment | Contraindicated in acute hepatic injury. For mild to moderate hepatic impairment (Child-Pugh class A/B), reduce starting dose by 50% and titrate slowly. For severe hepatic impairment (Child-Pugh class C), use is not recommended. |
| Pediatric use | Safety and efficacy in pediatric patients have not been established. No standard weight-based dosing guidelines are available. |
| Geriatric use | In elderly patients (≥65 years), start at the lower end of the dosing range (e.g., 120–180 mg once daily) due to increased potential for bradycardia and hypotension; titrate cautiously. |
| 1st trimester | Associated with fetal bradycardia and hypotension; avoid use. May cause reduced placental perfusion. |
| 2nd trimester | Avoid due to risk of fetal bradycardia and impaired fetal growth. |
| 3rd trimester | Avoid; may cause uterine contractions and fetal bradycardia. Consider alternative therapy. |
Clinical note
Comprehensive clinical and safety monograph for CARTIA XT (CARTIA XT).
| Placental transfer | Diltiazem crosses the placenta (fetal serum concentrations approximately 50% of maternal). |
| Breastfeeding | Diltiazem is excreted into breast milk in small amounts; levels are low but may cause bradycardia or hypotension in the infant. Monitor infant for side effects. Alternative agents may be preferred, especially when breastfeeding a premature or low-birth-weight infant. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | FDA Pregnancy Category C. First trimester: No adequate studies; potential for embryotoxicity. Second and third trimesters: May cause fetal bradycardia, hypotension, hypoglycemia; risk of intrauterine growth restriction. Use only if benefit outweighs risk. |
| Fetal Monitoring | Maternal: Heart rate, blood pressure, ECG in high-risk patients. Fetal: Heart rate monitoring during labor; consider ultrasound for growth assessment if used long-term. |
| Fertility Effects | No specific studies in humans. Animal studies show no impairment of fertility at therapeutic doses. Theoretical risk of reduced uteroplacental blood flow, but clinical significance unknown. |
■ FDA Black Box Warning
None
| 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 congestionAtrial fibrillation or atrial flutter with accessory bypass tract (e.g., WPW syndrome)Known hypersensitivity to diltiazem
| Precautions | Heart failure: may worsen systolic function due to negative inotropic effects, Sick sinus syndrome or AV block: risk of bradycardia, heart block, Concomitant beta-blocker use: increased risk of bradycardia, heart failure, Hepatic impairment: reduce dose, Renal impairment: use caution, Abrupt discontinuation: may cause angina exacerbation, Sinus bradycardia: monitor heart rate |
| Food/Dietary | Avoid grapefruit and grapefruit juice as they can increase diltiazem levels and risk of side effects. Avoid high-fat meals close to dosing as they may affect absorption. Limit alcohol intake as it may worsen hypotension or dizziness. |
| Clinical Pearls | CARTIA XT is a sustained-release formulation of diltiazem, a calcium channel blocker. Avoid use in patients with sick sinus syndrome or second/third-degree AV block without a pacemaker. Titrate slowly to prevent hypotension. Monitor heart rate and blood pressure regularly. Use with caution in hepatic or renal impairment. Can be used for rate control in atrial fibrillation but not for conversion. Swallow capsules whole; do not crush or chew. |
| Patient Advice | Take this medication exactly as prescribed, usually once daily. Swallow the capsule whole; do not crush, chew, or open it. · Do not stop taking this medication suddenly without consulting your doctor, as it may worsen your condition. · Avoid drinking grapefruit juice or eating grapefruit while taking this medication. · Inform your doctor if you experience dizziness, lightheadedness, slow heartbeat, swelling of ankles/feet, or shortness of breath. · This medication may cause dizziness or drowsiness; avoid driving or operating machinery until you know how it affects you. · Keep a regular schedule for taking this medication to maintain consistent levels in your blood. |
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