Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
CIMETIDINE HYDROCHLORIDE IN SODIUM CHLORIDE 0.9% IN PLASTIC CONTAINER vs AMINOPHYLLINE IN SODIUM CHLORIDE 0.45%
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Competitive antagonist of histamine at H2 receptors on gastric parietal cells, reducing gastric acid secretion (basal and stimulated) by inhibiting c AMP production.
Aminophylline is a complex of theophylline and ethylenediamine, acting as a phosphodiesterase inhibitor, increasing intracellular c AMP levels; nonselective adenosine receptor antagonist; enhances cardiac inotropy, bronchodilation, and CNS stimulation.
Treatment of active duodenal ulcer,Maintenance therapy for duodenal ulcer,Treatment of active benign gastric ulcer,Treatment of erosive gastroesophageal reflux disease (GERD),Treatment of pathological hypersecretory conditions (e.g., Zollinger-Ellison syndrome),Prevention of upper gastrointestinal bleeding in critically ill patients (off-label),Prophylaxis of aspiration pneumonitis during anesthesia (off-label)
Treatment of acute bronchospasm in asthma and COPD,Reversal of dipyridamole-induced adverse effects during stress testing,Apnea of prematurity (off-label),Status asthmaticus (off-label)
300 mg intravenously every 6-8 hours or as continuous IV infusion at 37.5-50 mg/hour. Maximum 2400 mg/day.
Loading dose: 5-6 mg/kg IV over 20-30 minutes, then continuous infusion: 0.5-0.7 mg/kg/hour IV.
2-3 hours in normal renal function, prolonged to >8 hours in severe renal impairment (Cr Cl <20 m L/min).
Terminal elimination half-life is 6-12 hours in adults, 1-5 hours in children (due to faster clearance), 20-30 hours in premature neonates, and 10-15 hours in patients with hepatic cirrhosis or heart failure. Clinical context: dosing interval adjustment required based on half-life; prolonged half-life in hepatic impairment or cardiac decompensation increases risk of toxicity.
Metabolized primarily in the liver via CYP450 enzymes, including CYP1A2, CYP2C19, CYP2D6, and CYP3A4; undergoes sulfoxidation and N-demethylation.
Hepatic via cytochrome P450 enzymes (CYP1A2, CYP3A4, CYP2E1); saturable kinetics; extensive first-pass metabolism.
Renal (75% as unchanged drug via glomerular filtration and tubular secretion); hepatic metabolism (25%); fecal (<10%).
Renal excretion of unchanged theophylline (10-20%) and metabolites (80-90%). In neonates, renal excretion of unchanged drug is higher (up to 50%). Biliary/fecal excretion is negligible.
13-25% bound to plasma proteins (albumin and alpha-1-acid glycoprotein).
Approximately 40% bound to plasma proteins, mainly albumin. In neonates, preterm infants, and patients with hepatic cirrhosis, protein binding is reduced (free fraction increases). Binding is also saturable at high theophylline concentrations.
1-2 L/kg, indicating extensive distribution into tissues, including liver, kidney, and gastric mucosa.
Volume of distribution is approximately 0.45 L/kg (range 0.3-0.7 L/kg) in adults. In neonates, Vd is larger (~0.6-0.8 L/kg). Clinical meaning: Vd indicates extensive distribution into body water; loading doses are calculated using Vd (e.g., 1 mg/kg raises serum concentration by ~2 mcg/m L).
Oral: 60-70% (first-pass metabolism); IM: 100% bioequivalent to IV.
Oral immediate-release: 100% (well absorbed). Rectal: 80-100% (absorption may be erratic). IV: 100%. No significant first-pass metabolism.
Cr Cl 10-50 m L/min: 300 mg every 12 hours. Cr Cl <10 m L/min: 300 mg every 24 hours.
No specific dose adjustment required for GFR >10 m L/min. For GFR <10 m L/min, reduce infusion rate by 50%.
No specific adjustment recommended. In severe hepatic impairment, reduce dose or prolong interval due to increased half-life; use with caution.
Child-Pugh Class A: reduce dose by 25%; Class B: reduce dose by 50%; Class C: reduce dose by 75%.
Neonates: 5-10 mg/kg/day IV divided every 8-12 hours. Children: 20-40 mg/kg/day IV divided every 6 hours, max 800 mg/day.
Loading dose: 5-6 mg/kg IV over 20-30 minutes; continuous infusion: 0.5-0.7 mg/kg/hour (age-dependent, with lower doses for younger children).
Reduce dose or prolong interval due to age-related renal impairment; consider creatinine clearance and adjust accordingly.
Elderly patients may have reduced clearance; consider starting at the lower end of dosing range (e.g., 0.3-0.5 mg/kg/hour) and titrate based on serum levels.
No FDA boxed warning for cimetidine hydrochloride.
Theophylline toxicity is dose-related and can be fatal; monitor serum theophylline levels closely; use with caution in patients with risk factors for reduced clearance (e.g., hepatic impairment, heart failure, elderly).
May cause confusion and delirium, especially in elderly or renally impaired patients; dose adjustment required for renal impairment.,Potential for drug interactions due to inhibition of CYP450 enzymes; monitor for interactions with warfarin, theophylline, phenytoin, lidocaine, and others.,Avoid rapid intravenous administration to prevent cardiac arrhythmias (bradycardia, hypotension).,Reversible gynecomastia and impotence may occur with prolonged use.,Neutropenia and thrombocytopenia reported rarely.
Narrow therapeutic index; severe toxicity can occur at levels >20 mcg/m L,Seizures and arrhythmias may occur without preceding symptoms,Variable clearance due to drug interactions, disease states, age, and smoking,Use with caution in peptic ulcer disease, seizure disorders, hyperthyroidism, and cardiac disease
Known hypersensitivity to cimetidine or any component of the formulation.,Use with caution in patients with renal impairment (dose adjustment required); contraindicated in patients with severe renal impairment if unable to adjust dose.
Hypersensitivity to aminophylline or any component,Hypersensitivity to theophylline or ethylenediamine,Cardiac arrhythmias requiring immediate therapy (relative)
Avoid alcohol, caffeine, and spicy foods as they may exacerbate gastric irritation. Cimetidine can increase caffeine levels; limit caffeine intake. No significant food-drug interactions, but a high-protein meal may delay absorption when given orally, though IV route bypasses this.
Avoid high-dose caffeine (coffee, tea, energy drinks, chocolate) as it may increase risk of side effects like nausea, anxiety, and tachycardia. Charcoal-broiled foods and a high-protein diet may increase theophylline clearance. Consistent dietary intake is recommended.
Cimetidine crosses the placenta. First trimester: No increased risk of major malformations in human studies, but animal studies show fetal effects at high doses. Second and third trimesters: Risk of transient neonatal hepatic dysfunction and possible androgen anti-androgen effects; use only if clearly needed.
First trimester: Limited data; no increased risk of major malformations observed in human studies. Second and third trimesters: Risk of fetal tachycardia and jitteriness with high maternal doses; may cause transient neonatal tachycardia with chronic use. No documented teratogenicity.
Cimetidine is excreted into breast milk; milk-to-plasma ratio approximately 0.5-1.0. Due to potential for adverse effects (e.g., CNS stimulation, gastric p H alteration) in nursing infants, caution is advised. Consider alternatives, especially while nursing a premature or jaundiced infant.
Aminophylline/theophylline is excreted into breast milk with an M/P ratio of approximately 0.6-0.7. Infant exposure is low (about 1-10% of maternal dose). Irritability and insomnia reported rarely. Use with caution, monitor infant for signs of theophylline toxicity.
Pregnancy may alter cimetidine pharmacokinetics (increased volume of distribution, unchanged clearance). No specific dose adjustment is recommended, but monitor for therapeutic effect and toxicity. In severe renal impairment (creatinine clearance <30 m L/min), reduce dose to 300 mg every 12 hours.
Pregnancy decreases theophylline clearance by approximately 20-30% during third trimester. Dosing adjustments may be required: monitor serum levels and adjust dose to maintain therapeutic levels. Postpartum clearance returns rapidly, requiring downward dose adjustment.
Cimetidine is a potent inhibitor of CYP450 enzymes, notably CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4. Monitor for drug interactions, especially with warfarin, theophylline, phenytoin, and lidocaine. Adjust doses of these drugs when co-administered. Cimetidine can cause confusion in elderly patients, particularly with high doses or renal impairment. Administer IV slowly over at least 20 minutes to avoid hypotension and cardiac arrhythmias. In renal impairment (Cr Cl <30 m L/min), reduce dose to 300 mg q12h. For acid suppression, IV route is reserved for when oral therapy is not feasible.
Aminophylline is a bronchodilator that releases theophylline. Monitor serum theophylline levels (therapeutic range 5-15 mcg/m L). Avoid in patients with active peptic ulcer disease, seizure disorders, or hypersensitivity to xanthines. Caution in hepatic impairment, heart failure, and elderly due to reduced clearance. Drug interactions with cimetidine, ciprofloxacin, and macrolides increase theophylline levels.
Do not stop taking this medication abruptly without consulting your doctor.,Report any signs of confusion, especially if you are elderly or have kidney problems.,Avoid smoking, as it can increase stomach acid and reduce drug effectiveness.,Notify your doctor if you are taking blood thinners (e.g., warfarin), asthma medications (e.g., theophylline), or seizure medications (e.g., phenytoin).,This medication may cause dizziness or drowsiness; avoid driving until you know how it affects you.,Do not take over-the-counter pain relievers like ibuprofen or aspirin unless approved by your doctor, as they can worsen stomach issues.
Do not exceed prescribed dose. Take exactly as directed.,Avoid caffeine-containing products (coffee, tea, cola, chocolate) as they may increase side effects.,Report symptoms of toxicity: nausea, vomiting, insomnia, rapid heart rate, palpitations, or seizures.,Do not crush or chew extended-release forms; take with food if gastric upset occurs.,Do not stop abruptly without consulting your healthcare provider.
"Axitinib, a tyrosine kinase inhibitor used in renal cell carcinoma, is primarily metabolized by CYP3A4 and also by CYP1A2 and CYP2C19. Cimetidine, a histamine H2 receptor antagonist, is a known inhibitor of multiple CYP450 enzymes including CYP1A2, CYP2C19, and CYP3A4. Co-administration of cimetidine may decrease the metabolism of axitinib, potentially leading to increased plasma concentrations of axitinib, thereby enhancing its therapeutic effects and increasing the risk of dose-dependent toxicities such as hypertension, proteinuria, and gastrointestinal perforation."
"Cimetidine, a potent inhibitor of CYP1A2 and other cytochrome P450 enzymes, can reduce the metabolism of zolmitriptan, which is partially metabolized by CYP1A2. This leads to increased serum concentrations of both drugs, potentially enhancing the risk of zolmitriptan-related adverse effects such as serotonin syndrome, hypertension, and cardiac events. Concurrent use may also elevate cimetidine levels, though the clinical significance is less clear."
"Cimetidine, a potent inhibitor of cytochrome P450 (CYP) enzymes, particularly CYP2D6 and CYP3A4, significantly decreases the metabolism of fesoterodine, a prodrug that is rapidly converted to its active metabolite 5-hydroxymethyl tolterodine (5-HMT). This metabolic inhibition can substantially elevate the serum concentrations of the active metabolite, increasing the risk of anticholinergic adverse effects such as dry mouth, constipation, blurred vision, urinary retention, and potential cognitive impairment. In patients with renal or hepatic impairment, the elevations may be even more pronounced, warranting caution."
"Concurrent administration of aminophylline, a xanthine derivative bronchodilator that is metabolized primarily by CYP1A2 and to a lesser extent CYP3A4, may reduce the clearance of ranolazine, an antianginal agent predominantly metabolized by CYP3A4 and to a lesser extent CYP2D6. Aminophylline can inhibit CYP3A4 activity, leading to increased ranolazine plasma concentrations, which elevates the risk of dose-dependent adverse effects such as QTc prolongation, dizziness, and syncope. This interaction is clinically significant and may necessitate dose adjustment or alternative therapy."
"Asunaprevir, a potent inhibitor of the drug transporter OATP1B1, can significantly decrease the serum concentration of aminophylline, a theophylline salt, likely by reducing its intestinal absorption or increasing its hepatic clearance. This interaction may lead to reduced therapeutic efficacy of aminophylline, potentially worsening respiratory symptoms in patients with asthma or COPD. Close monitoring and dose adjustment of aminophylline are recommended during coadministration with asunaprevir."
"Aminophylline, a bronchodilator, inhibits the metabolism of tibolone, a synthetic steroid hormone used for hormone replacement therapy, primarily through competitive inhibition of cytochrome P450 (CYP) 3A4 isoenzyme. This results in increased plasma concentrations of tibolone and its active metabolites, potentiating its hormonal effects and increasing the risk of adverse events such as thromboembolism, endometrial hyperplasia, or breast tenderness. Clinically, coadministration may require dose adjustments and careful monitoring for signs of estrogenic excess."
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about CIMETIDINE HYDROCHLORIDE IN SODIUM CHLORIDE 0.9% IN PLASTIC CONTAINER vs AMINOPHYLLINE IN SODIUM CHLORIDE 0.45%, answered by our medical review team.
CIMETIDINE HYDROCHLORIDE IN SODIUM CHLORIDE 0.9% IN PLASTIC CONTAINER is a Electrolyte that works by Competitive antagonist of histamine at H2 receptors on gastric parietal cells, reducing gastric acid secretion (basal and stimulated) by inhibiting c AMP production.. AMINOPHYLLINE IN SODIUM CHLORIDE 0.45% is a Electrolyte that works by Aminophylline is a complex of theophylline and ethylenediamine, acting as a phosphodiesterase inhibitor, increasing intracellular c AMP levels; nonselective adenosine receptor antagonist; enhances cardiac inotropy, bronchodilation, and CNS stimulation.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between CIMETIDINE HYDROCHLORIDE IN SODIUM CHLORIDE 0.9% IN PLASTIC CONTAINER and AMINOPHYLLINE IN SODIUM CHLORIDE 0.45% depend on the specific clinical indication. These are both Electrolyte agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of CIMETIDINE HYDROCHLORIDE IN SODIUM CHLORIDE 0.9% IN PLASTIC CONTAINER is: 300 mg intravenously every 6-8 hours or as continuous IV infusion at 37.5-50 mg/hour. Maximum 2400 mg/day.. The standard adult dose of AMINOPHYLLINE IN SODIUM CHLORIDE 0.45% is: Loading dose: 5-6 mg/kg IV over 20-30 minutes, then continuous infusion: 0.5-0.7 mg/kg/hour IV.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
A moderate-severity drug interaction has been identified when combining CIMETIDINE HYDROCHLORIDE IN SODIUM CHLORIDE 0.9% IN PLASTIC CONTAINER and AMINOPHYLLINE IN SODIUM CHLORIDE 0.45%. The metabolism of Cimetidine can be decreased when combined with Aminophylline. Consult your prescriber before combining these medications.
The maternal-fetal safety profiles differ. CIMETIDINE HYDROCHLORIDE IN SODIUM CHLORIDE 0.9% IN PLASTIC CONTAINER is classified as Category A/B. Cimetidine crosses the placenta. First trimester: No increased risk of major malformations in human studies, but animal studies show fetal effects at high doses. Second and third t. AMINOPHYLLINE IN SODIUM CHLORIDE 0.45% is classified as Category A/B. First trimester: Limited data; no increased risk of major malformations observed in human studies. Second and third trimesters: Risk of fetal tachycardia and jitteriness with high . Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.