MENTEX SYRUP 125ML

Indications

Approved Uses

Symptomatic relief of cough and upper respiratory allergy/cold symptoms including nasal congestion, rhinorrhea, sneezing and watery/itchy eyes (e.g., common cold and allergic rhinitis/hay fever).

Off-Label Uses

No appropriate off-label uses are recommended for this combination product; diphenhydramine alone is sometimes used for short-term insomnia or motion sickness, but the presence of pseudoephedrine and dextromethorphan makes this combination unsuitable for those purposes.

Dosage & Administration

Dose Adjustment Notes

Use caution in older adults (greater anticholinergic/CNS sensitivity) and consider lower doses/avoidance; use caution in significant hepatic impairment (diphenhydramine/dextromethorphan metabolism) and in renal impairment (pseudoephedrine renal elimination), with dose/interval adjustment as clinically needed.

How to Take

Shake well before use. Measure each dose with a calibrated measuring device (oral syringe or medicine cup/spoon supplied). May be taken with or without food; take with food if stomach upset occurs. Do not exceed the prescribed dose/frequency.

Side Effects

Common Side Effects

Drowsiness/sedation, dizziness, dry mouth/nose/throat, blurred vision, nausea, constipation, urinary retention (especially in BPH), nervousness/restlessness/insomnia, headache; may increase heart rate and blood pressure and cause palpitations.

Side Effect Frequency

Common/very common: drowsiness/sedation, dizziness, dry mouth/throat, blurred vision, nausea/GI upset. Common (pseudoephedrine-related): nervousness/restlessness/insomnia, palpitations/tachycardia. Less common/rare: urinary retention (especially in BPH), hypertension, rash; paradoxical CNS excitation in children; hallucinations mainly with supratherapeutic dextromethorphan exposure.

Safety & Warnings

Contraindications

Hypersensitivity to components; concomitant use of MAO inhibitors or within 14 days; severe hypertension or severe coronary artery disease; narrow-angle glaucoma; urinary retention/prostatic hypertrophy; use in neonates/premature infants; avoid with other sympathomimetics/duplicate decongestants.

Warnings & Precautions

Avoid use with MAO inhibitors or within 14 days; caution in hypertension/cardiovascular disease, hyperthyroidism, diabetes, glaucoma, prostatic hypertrophy/urinary retention, and chronic respiratory disease; may cause sedation-avoid driving/alcohol/CNS depressants; avoid duplicate therapy with other antihistamines, decongestants, or cough suppressants; misuse/abuse risk with dextromethorphan at high doses.

Age Restriction

Not recommended in children under 6 years of age (and contraindicated under 2 years).

Drug Interactions

Drug Interactions

MAO inhibitors (contraindicated; hypertensive crisis/serotonin toxicity risk); alcohol and other CNS depressants (additive sedation/respiratory depression); other sympathomimetics/decongestants (additive cardiovascular/CNS stimulation); serotonergic drugs and CYP2D6 inhibitors (↑ dextromethorphan exposure/serotonin syndrome risk); anticholinergics/TCAs (additive anticholinergic effects); antihypertensives (pseudoephedrine may blunt effect).

Interaction Severity

MAJOR/Contraindicated: MAO inhibitors within 14 days (risk of hypertensive crisis from pseudoephedrine and potential serotonin syndrome/toxicity with dextromethorphan). MODERATE: Alcohol/other CNS depressants (additive sedation), other sympathomimetics/decongestants (additive BP/HR effects), serotonergic drugs or strong CYP2D6 inhibitors (e.g., fluoxetine/paroxetine/quinidine) increasing dextromethorphan exposure and serotonin syndrome risk, tricyclics/anticholinergics (additive anticholinergic effects).

Food Interaction

No restriction

Special Populations

Kidney Impairment

Use with caution; consider dose reduction or extended interval in moderate-to-severe renal impairment.

Storage & Patient Advice

Missed Dose

Take as soon as remembered; skip if near the time of the next dose. Do not double the dose.

Stopping the Medicine

No tapering is required for short-term symptomatic use; may stop when symptoms resolve. Do not exceed recommended duration/dose; seek medical advice if symptoms persist or if used regularly for an extended period.

Overdose

Symptoms: CNS depression or agitation, anticholinergic toxicity (dry mouth, mydriasis, hyperthermia, urinary retention), tachycardia/arrhythmias, hypertension, hallucinations, seizures, and possible respiratory depression; Management: urgent medical care, activated charcoal if appropriate, supportive care (airway/ventilation, fluids), benzodiazepines for seizures/agitation, treat hyperthermia, and consider physostigmine only in severe anticholinergic delirium under expert supervision.

Patient Counseling

May cause significant drowsiness and impaired coordination-avoid driving/operating machinery. Avoid alcohol and other sedatives. Do not use with MAO inhibitors or within 14 days of stopping them. Do not take with other cough/cold/allergy products (risk of duplicate diphenhydramine/dextromethorphan/pseudoephedrine). Use caution/seek advice if you have hypertension/heart disease, hyperthyroidism, diabetes, glaucoma, or prostate enlargement/urinary retention. Measure doses with a proper device; do not exceed prescribed dosing. Seek medical advice if symptoms persist >7 days, worsen, or are accompanied by high fever, rash, or breathing difficulty.

Monitoring Requirements

No routine lab monitoring is required, but clinically monitor for sedation/CNS impairment, anticholinergic effects (urinary retention, constipation, blurred vision), and blood pressure/heart rate in patients with hypertension, cardiovascular disease, hyperthyroidism, or when combined with other sympathomimetics.

Pharmacology

Mechanism of Action

Diphenhydramine: first-generation H1 receptor inverse agonist/antagonist with anticholinergic and sedative effects. Dextromethorphan: centrally acting antitussive that suppresses the medullary cough center (sigma-1 activity and NMDA antagonism contribute). Pseudoephedrine: indirect/direct sympathomimetic stimulating mainly alpha-adrenergic receptors (and some beta activity) causing nasal mucosal vasoconstriction and decongestion.

Duration of Effect

Approximately 4-6 hours.

Half-Life

Diphenhydramine: 4-8 hours; Dextromethorphan: 2-4 hours (extensive metabolizers), 24 hours (poor metabolizers); Pseudoephedrine: 5-8 hours

Metabolism

Diphenhydramine: extensive hepatic metabolism (primarily CYP2D6-mediated N-demethylation; additional minor pathways). Dextromethorphan: extensive hepatic metabolism mainly by CYP2D6 to dextrorphan (also CYP3A4 contributes). Pseudoephedrine: minimal metabolism; minor hepatic N-demethylation, with most eliminated unchanged.

Product Information

Available Dosage Forms

Syrup

Composition per Dose

Each 5 ml: Diphenhydramine hydrochloride 12.5 mg + Dextromethorphan hydrobromide 15 mg + Pseudoephedrine hydrochloride 30 mg

Generic Availability

Yes

OTC Alternatives

In Saudi Arabia this specific product is prescription-only per verified SFDA legal status; however, depending on local regulations, single-ingredient or other cough/cold products may be available OTC-patients should confirm with a pharmacist and avoid duplicating ingredients.

Symptom Target

Multi-symptom

Sedating

Yes

Reviewed by Al Mujtama Pharmacy Medical Review Team. Last reviewed 06-05-2026