HISTALOG
Clinical safety rating: caution
Comprehensive clinical and safety monograph for HISTALOG (HISTALOG).
Histalog (betazole) is a histamine H2 receptor agonist that stimulates gastric acid secretion by directly acting on parietal cells in the stomach.
| Metabolism | Primarily hepatic metabolism via N-methylation and oxidative deamination; metabolites excreted in urine. |
| Excretion | Primarily renal excretion of unchanged drug (approximately 80-90%) with the remainder as metabolites; biliary excretion accounts for <10%. |
| Half-life | Terminal elimination half-life is approximately 1.5-2 hours in adults with normal renal function; may be prolonged in renal impairment. |
| Protein binding | <15% bound to plasma proteins (notably albumin). |
| Volume of Distribution | Approximately 0.5 L/kg, indicating distribution primarily into extracellular fluid. |
| Bioavailability | Not applicable by oral route (used parenterally only); 100% bioavailability after subcutaneous or intramuscular injection. |
| Onset of Action | Subcutaneous: 30-45 minutes; Intramuscular: 15-30 minutes. |
| Duration of Action | Subcutaneous: 2-3 hours; Intramuscular: 1.5-2.5 hours. Clinical effect correlates with histamine release; shorter with higher gastric acid output. |
1.7 mg subcutaneously once, as a single dose for gastric acid secretion testing.
| Dosage form | INJECTABLE |
| Renal impairment | No specific dosage adjustment provided in manufacturer labeling. Caution in severe renal impairment due to potential accumulation. |
| Liver impairment | No specific dosage adjustment provided in manufacturer labeling. Use caution in severe hepatic impairment. |
| Pediatric use | Safety and efficacy in pediatric patients have not been established. No specific dosing recommendations. |
| Geriatric use | No specific dosage adjustment provided; however, consider age-related renal and hepatic function changes. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for HISTALOG (HISTALOG).
| Breastfeeding | No data on excretion into breast milk. Due to lack of safety data and potential for adverse effects (e.g., gastric acid stimulation, histamine-related effects) in the nursing infant, breastfeeding is not recommended during Histalog administration. M/P ratio unknown. |
| Teratogenic Risk | Histalog (betazole) is a histamine analogue used as a diagnostic agent for gastric acid secretion. Data on teratogenicity are limited. In animal studies, high doses caused fetal resorptions and skeletal anomalies. First trimester exposure theoretically could cause uterine contractions due to histaminergic activity, potentially increasing miscarriage risk. Second and third trimester use may induce premature labor. Avoid in pregnancy unless clearly needed. |
■ FDA Black Box Warning
None.
| Serious Effects |
["Hypersensitivity to betazole or any component of the formulation","Severe hypotension","Uncontrolled asthma","Pheochromocytoma"]
| Precautions | ["May cause severe hypotension, especially in patients with cardiovascular disease","Contraindicated in patients with known hypersensitivity to histamine or analogs","Use with caution in patients with asthma, peptic ulcer disease, or pheochromocytoma"] |
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| Fetal Monitoring | Monitor maternal vital signs (blood pressure, heart rate) during and after administration due to possible histamine-mediated hypotension or tachycardia. Observe for signs of premature labor (uterine contractions) in pregnant patients. In neonates exposed in utero, monitor for transient gastrointestinal hypersecretion, flushing, or hypotension. |
| Fertility Effects | No specific studies on fertility. Histalog's histaminergic effects could theoretically alter reproductive tract function, but no human data indicate impaired fertility. |