AXID AR
Clinical safety rating: caution
Comprehensive clinical and safety monograph for AXID AR (AXID AR).
Nizatidine is a competitive, reversible inhibitor of histamine at the H2-receptors of the gastric parietal cells, reducing gastric acid secretion.
| Metabolism | Metabolized extensively in the liver via CYP450 system, primarily CYP1A2, CYP2C19, and CYP3A4; also undergoes renal elimination. |
| Excretion | Primarily renal; ~60% of an oral dose is excreted unchanged in urine via tubular secretion and glomerular filtration. Hepatic metabolism accounts for ~30% (N-oxidation, S-oxidation, and N-demethylation), with metabolites and small amounts of parent drug eliminated in feces via bile. |
| Half-life | Terminal elimination half-life is 1.5–2.5 hours (mean ~2 hours) in patients with normal renal function. In elderly or those with creatinine clearance <50 mL/min, half-life may extend to 4–6 hours, necessitating dose adjustment. |
| Protein binding | ~35% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Approximately 1.4–1.5 L/kg, indicating extensive extravascular distribution. Total Vd ~100 L for a 70 kg adult. |
| Bioavailability | Oral bioavailability is approximately 90–100%, with minimal first-pass metabolism. Food may slightly delay absorption but does not significantly affect total bioavailability. |
| Onset of Action | Oral: Onset of gastric acid suppression occurs within 30–60 minutes, with peak effect at 1–2 hours. Single oral dose provides rapid relief of heartburn. |
| Duration of Action | Duration of acid suppression is dose-dependent; a single 75 mg oral dose relieves symptoms for up to 12 hours. However, gastric pH remains elevated for 8–12 hours after dosing. |
75 mg orally once daily at bedtime for heartburn relief; maximum 150 mg per 24 hours.
| Dosage form | TABLET |
| Renal impairment | For CrCl 20-50 mL/min: reduce dose to 75 mg every other day; for CrCl <20 mL/min: 75 mg every third day. |
| Liver impairment | No dose adjustment recommended for Child-Pugh Class A or B; Child-Pugh Class C: use with caution, consider 75 mg every other day. |
| Pediatric use | Not approved for use in children; safety and efficacy not established. |
| Geriatric use | Initiate at 75 mg daily; increase only if clinically indicated; monitor renal function and consider renal adjustment based on CrCl. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for AXID AR (AXID AR).
| Breastfeeding | Nizatidine is excreted in human milk in low concentrations. M/P ratio not established. Use with caution in nursing mothers; consider potential for adverse effects in infant. |
| Teratogenic Risk | FDA Pregnancy Category B. No evidence of teratogenicity in animal studies. Insufficient human data; risk cannot be excluded. Avoid in first trimester unless clearly needed. |
| Fetal Monitoring |
■ FDA Black Box Warning
No FDA black box warnings.
| Serious Effects |
["Known hypersensitivity to nizatidine or other H2 receptor antagonists"]
| Precautions | ["Symptomatic response does not preclude presence of gastric malignancy","Adjust dose in moderate to severe renal impairment (creatinine clearance <50 mL/min)","Possible cross-sensitivity with other H2 antagonists","May cause confusion, delirium, or hallucinations in elderly or severely ill patients","Avoid use in patients with a history of acute porphyria"] |
| Food/Dietary | No significant food interactions; can be taken with or without food. Avoid spicy, fatty, or acidic foods that may trigger heartburn. |
Loading safety data…
| No specific fetal monitoring required. Monitor maternal renal and hepatic function if long-term use. |
| Fertility Effects | No known adverse effects on human fertility based on animal studies. |
| Clinical Pearls |
| AXID AR (nizatidine) is an H2-receptor antagonist available over the counter for heartburn. Onset of action is within 1 hour; avoid use with antacids within 1 hour. Does not require renal dose adjustment in mild impairment but caution in CrCl <50 mL/min. May cause thrombocytopenia rarely; monitor CBC in elderly or on long-term therapy. |
| Patient Advice | Take exactly as directed; do not exceed 2 tablets in 24 hours. · Swallow tablet whole with a glass of water; do not chew or crush. · Avoid alcohol, which can worsen heartburn. · If symptoms persist >2 weeks, consult a healthcare provider. · Can be taken without regard to meals. |