Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
PROMETHAZINE W/ CODEINE vs ACUVUE THERAVISION WITH KETOTIFEN
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: June 2026 · OpiCalc Medical Review Team
Codeine is a prodrug converted to morphine, a mu-opioid receptor agonist, which inhibits nociceptive transmission; promethazine is a phenothiazine derivative with H1-receptor antagonism, anticholinergic, and antiemetic effects.
Ketotifen is a selective histamine H1-receptor antagonist and mast cell stabilizer that inhibits the release of inflammatory mediators such as histamine and leukotrienes from mast cells.
Relief of mild to moderate pain,Cough suppression
FDA-approved for the prevention and treatment of ocular itching associated with allergic conjunctivitis
10 m L (1 mg codeine, 6.25 mg promethazine per 5 m L) orally every 4-6 hours as needed for cough. Maximum: 60 m L per day. Do not exceed 5 days.
One drop in each affected eye twice daily (approximately 8 hours apart) as needed. The lens should be removed prior to instillation and can be reinserted after at least 10 minutes.
Promethazine: 10-19 hours (terminal). Codeine: 2.5-3.5 hours (terminal); prolonged in renal impairment.
12 hours (terminal elimination half-life; clinical context: twice-daily dosing needed for continuous effect).
Codeine: Hepatic via CYP2D6 (to morphine), CYP3A4 (to norcodeine); Promethazine: Hepatic via CYP2B6, CYP2D6, and glucuronidation.
Not significantly metabolized in the eye; systemic absorption is minimal. After systemic absorption, it is metabolized primarily via glucuronidation and oxidation, with a half-life of approximately 12 hours.
Promethazine: renal (70% as metabolites, <1% unchanged), fecal (20-30%). Codeine: renal (90%, of which 5-10% unchanged, rest as metabolites), fecal (minor).
Renal (approximately 50% as unchanged drug, 30% as metabolites); biliary/fecal elimination accounts for <10%.
Promethazine: 93% (primarily to albumin). Codeine: 7-25% (to albumin).
99% (primarily albumin and alpha-1-acid glycoprotein).
Promethazine: 5-14 L/kg (extensive tissue distribution). Codeine: 3-6 L/kg (widely distributed).
2.4 L/kg (high tissue distribution, including ocular tissues).
Promethazine: oral 25% (due to first-pass metabolism), IM ~88%. Codeine: oral 50-70% (converted to morphine via CYP2D6), IM ~80%.
Ocular topical: ~0.1% systemic; oral: 70% (not relevant for contact lens application).
e GFR 30-59 m L/min: Administer every 6 hours; e GFR 15-29 m L/min: Administer every 8 hours; e GFR <15 m L/min: Avoid use or consider extended interval due to accumulation of codeine metabolites.
No dosage adjustment required based on renal function; systemic absorption is minimal.
Child-Pugh A: No adjustment; Child-Pugh B: Reduce dose by 50% or extend interval; Child-Pugh C: Avoid use due to risk of hepatic encephalopathy and impaired codeine metabolism.
No dosage adjustment required based on hepatic function; systemic absorption is minimal.
Use not recommended in children <12 years due to risk of respiratory depression. For ages 12-18: 10-15 m L (with caution) every 4-6 hours as needed. Weight-based dosing: 0.5-1 mg/kg/dose of codeine (max 60 mg/day) with promethazine 0.25-0.5 mg/kg/dose (max 25 mg/dose).
Safety and efficacy in pediatric patients below 3 years of age have not been established. For children 3 years and older, administer one drop in each affected eye twice daily.
Initiate with 5 m L orally every 6-8 hours; titrate cautiously due to increased sensitivity, risk of sedation, and anticholinergic effects. Maximum daily dose: 40 m L. Avoid in patients with significant cognitive impairment.
No specific dosage adjustment is required for elderly patients; use same dosing as for adults.
Warning: Risk of respiratory depression, especially in children; fatal respiratory depression can occur. Codeine is contraindicated in children <12 years and should not be used in children <18 years after tonsillectomy/adenoidectomy. Also, risk of opioid addiction, abuse, and misuse.
None
Respiratory depression, risk of opioid-induced hyperalgesia, severe hypotension, seizures in patients with porphyria, sedation and impaired motor skills, risk of serotonin syndrome when combined with serotonergic drugs, avoid abrupt discontinuation, use caution in elderly, hepatic/renal impairment, and respiratory disorders.
For topical ophthalmic use only; not for injection.,Contains benzalkonium chloride; soft contact lens wearers should remove lenses before application and wait at least 10 minutes before reinserting.,May cause transient stinging or burning upon instillation.,Use with caution in patients with known hypersensitivity to any component.
Hypersensitivity to codeine, promethazine, or any phenothiazine; children <12 years; postoperative management in children <18 years following tonsillectomy/adenoidectomy; significant respiratory depression; acute or severe bronchial asthma; GI obstruction; concurrent use of MAOIs or within 14 days.
Hypersensitivity to ketotifen or any component of the product.
Avoid alcohol; may enhance sedative effects. No specific food restrictions, but high-fat meals may delay absorption.
None reported.
PROMETHAZINE W/ CODEINE is contraindicated during all trimesters. First trimester: codeine is associated with increased risk of congenital malformations (cardiac, cleft palate) due to opioid receptor activation. Promethazine may cause mild neural tube defects. Second/third trimesters: codeine can cause fetal opioid dependence and neonatal abstinence syndrome; promethazine may cause respiratory depression and thrombocytopenia in neonates. Chronic use may lead to preterm birth and low birth weight. Do not use during labor and delivery due to risk of respiratory depression in the neonate.
Ketotifen ophthalmic solution has minimal systemic absorption (approximately 0.1% of administered dose). No adequate well-controlled studies in pregnant women. Animal studies showed no teratogenicity at doses up to 50 mg/kg/day orally. Risk to fetus is considered low when used topically as directed.
Breastfeeding not recommended. Codeine is excreted into breast milk with a milk-to-plasma (M/P) ratio of approximately 2.5-3.0 (for morphine, codeine active metabolite). In mothers who are CYP2D6 ultra-rapid metabolizers, codeine can lead to life-threatening respiratory depression in infants. Promethazine is excreted in low amounts but may cause sedation and apnea in neonates.
Ketotifen is excreted in human milk following oral administration; however, systemic absorption from ophthalmic use is negligible. M/P ratio not established for ophthalmic route. Consider benefit vs risk; caution in breastfeeding mothers.
Pregnancy is a contraindication; thus, dosing adjustments are not applicable. If unavoidable, use the lowest effective dose for the shortest duration, but no safe dose established. Avoid during third trimester due to risk of neonatal respiratory depression. Codeine pharmacokinetics in pregnancy: increased clearance due to enhanced hepatic blood flow and CYP2D6 induction, but this is not a basis for dose adjustment as risk outweighs benefit.
No dosage adjustment required. Use as directed; pharmacokinetic changes in pregnancy are not significant for topical ophthalmic route.
Promethazine with codeine is contraindicated in children <6 years due to risk of fatal respiratory depression. Avoid in patients with asthma or COPD. Use with caution with other CNS depressants. Monitor for signs of serotonin syndrome if combined with serotonergic drugs.
Ketotifen is a mast cell stabilizer and antihistamine; contact lens must be removed before instillation and may be reinserted after 10 minutes. Do not use while wearing contact lenses. Advise patient to wait at least 5 minutes between different eye drops. The preservative benzalkonium chloride may be absorbed by soft contact lenses.
May cause drowsiness; avoid driving or operating machinery.,Do not exceed recommended dose; risk of addiction and dependence.,Do not consume alcohol while taking this medication.,Take with food if gastrointestinal upset occurs.,Stop use and seek medical attention if breathing becomes difficult or you experience rash.
Remove contact lenses before using the drops and wait at least 10 minutes before reinserting.,Wash hands before use. Do not touch the dropper tip to any surface, including the eye.,Do not use if the solution changes color or becomes cloudy.,Use exactly as prescribed; do not use more often than directed.,If you miss a dose, use it as soon as possible. If it is almost time for the next dose, skip the missed dose and resume your regular schedule. Do not double the dose.,Contact your doctor if you experience eye pain, vision changes, or if symptoms persist or worsen.
"Promethazine, a phenothiazine derivative with strong anticholinergic and sedative properties, combined with levocabastine, a histamine H1-receptor antagonist, results in additive anticholinergic and central nervous system (CNS) depressant effects. This synergy can lead to excessive sedation, impaired cognitive and motor function, and increased risk of anticholinergic side effects such as dry mouth, urinary retention, and constipation. Clinically, patients may experience heightened drowsiness, dizziness, and confusion, posing risks for falls or accidents, particularly in elderly or debilitated individuals."
"The combination of promethazine and gabapentin enacarbil results in additive central nervous system (CNS) depression, leading to enhanced sedative effects, dizziness, and impaired cognitive or motor function. This interaction is primarily mediated by the synergistic pharmacodynamic actions of both drugs on GABAergic and histaminergic pathways, increasing the risk of excessive sedation, respiratory depression, and falls, particularly in elderly or debilitated patients. Clinical outcomes may include profound drowsiness, confusion, and increased risk of accidental injury, necessitating cautious dose titration and monitoring."
"Gabapentin, a GABA analog with central nervous system depressant effects, interacts pharmacodynamically with the antihistamine and anticholinergic agent Promethazine. Co-administration results in additive sedation, dizziness, and cognitive impairment due to enhanced central nervous system depression. This increases the risk of falls, respiratory depression, and impaired psychomotor function, particularly in elderly patients."
"Lisdexamfetamine, a prodrug of dextroamphetamine, increases central nervous system (CNS) arousal via dopamine and norepinephrine release, counteracting the sedative effects of ketotifen, a mast cell stabilizer with histamine H1-receptor antagonism and CNS depressant properties. The interaction results in reduced sedative efficacy of ketotifen, potentially affecting therapeutic outcomes in allergic conditions where sedation is beneficial, such as severe pruritus or urticaria. Clinically, patients may experience decreased drowsiness or sleepiness, which could be undesirable if ketotifen is prescribed specifically for its soporific effects."
"Pseudoephedrine, a sympathomimetic amine, exerts central nervous system (CNS) stimulant effects by indirectly activating adrenergic receptors, which can counteract the sedative properties of ketotifen, a histamine H1-receptor antagonist with mast cell stabilizing activity. This pharmacodynamic antagonism may reduce the therapeutic efficacy of ketotifen in managing allergic conditions, particularly its ability to cause drowsiness as a side effect. Clinically, patients may experience diminished sedation, potentially leading to decreased compliance or altered therapeutic outcomes in conditions where sedation is beneficial."
"Hydroxyamphetamine, an indirect-acting sympathomimetic amine, stimulates the release of norepinephrine from presynaptic nerve terminals, leading to activation of alpha- and beta-adrenergic receptors. This produces central nervous system (CNS) stimulation that may oppose the sedative effects of ketotifen, a histamine H1-receptor antagonist with sedative properties. Consequently, coadministration may result in reduced efficacy of ketotifen for sedation or sleep induction, potentially compromising its therapeutic benefit in conditions requiring CNS depression (e.g., allergic rhinitis, urticaria)."
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about PROMETHAZINE W/ CODEINE vs ACUVUE THERAVISION WITH KETOTIFEN, answered by our medical review team.
PROMETHAZINE W/ CODEINE is a Antihistamine / Antiemetic that works by Codeine is a prodrug converted to morphine, a mu-opioid receptor agonist, which inhibits nociceptive transmission; promethazine is a phenothiazine derivative with H1-receptor antagonism, anticholinergic, and antiemetic effects.. ACUVUE THERAVISION WITH KETOTIFEN is a Antihistamine / Mast Cell Stabilizer that works by Ketotifen is a selective histamine H1-receptor antagonist and mast cell stabilizer that inhibits the release of inflammatory mediators such as histamine and leukotrienes from mast cells.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between PROMETHAZINE W/ CODEINE and ACUVUE THERAVISION WITH KETOTIFEN depend on the specific clinical indication. These are agents from distinct pharmacological classes and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of PROMETHAZINE W/ CODEINE is: 10 m L (1 mg codeine, 6.25 mg promethazine per 5 m L) orally every 4-6 hours as needed for cough. Maximum: 60 m L per day. Do not exceed 5 days.. The standard adult dose of ACUVUE THERAVISION WITH KETOTIFEN is: One drop in each affected eye twice daily (approximately 8 hours apart) as needed. The lens should be removed prior to instillation and can be reinserted after at least 10 minutes.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between PROMETHAZINE W/ CODEINE and ACUVUE THERAVISION WITH KETOTIFEN in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. PROMETHAZINE W/ CODEINE is classified as Category A/B. PROMETHAZINE W/ CODEINE is contraindicated during all trimesters. First trimester: codeine is associated with increased risk of congenital malformations (cardiac, cleft palate) due. ACUVUE THERAVISION WITH KETOTIFEN is classified as Category A/B. Ketotifen ophthalmic solution has minimal systemic absorption (approximately 0.1% of administered dose). No adequate well-controlled studies in pregnant women. Animal studies showe. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.