MYFED
Clinical safety rating
cautionComprehensive clinical and safety monograph for MYFED (MYFED).
Pseudoephedrine is a sympathomimetic amine that acts as a decongestant by stimulating alpha-adrenergic receptors in the respiratory tract mucosa, causing vasoconstriction and reducing nasal congestion.
| Metabolism | Hepatic metabolism via N-demethylation to active metabolite; undergoes some phase I and phase II metabolism; excreted renally. |
| Excretion | Primarily renal (85-90% as unchanged drug) via glomerular filtration and tubular secretion; minor biliary/fecal excretion (5-10%). |
| Half-life | 3-5 hours in adults with normal renal function; prolonged to 12-24 hours in severe renal impairment (CrCl <30 mL/min). |
| Protein binding | 25-30% bound to serum albumin. |
| Volume of Distribution | 1-2 L/kg, indicating extensive tissue distribution. |
| Bioavailability | Oral: 60-70% due to first-pass metabolism. |
| Onset of Action | Oral: 30-60 minutes; Intravenous: within 5 minutes. |
| Duration of Action | 4-6 hours for oral; 3-5 hours for IV; extended in renal impairment. |
| Molecular Weight | 169.22 |
500 mg orally twice daily with meals.
| Dosage form | SYRUP |
| Renal impairment | GFR ≥60 mL/min: 500 mg twice daily. GFR 30-59: 500 mg once daily. GFR <30: 500 mg every other day. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 25%. Child-Pugh C: reduce dose by 50%. |
| Pediatric use | Not recommended for pediatric use; safety and efficacy not established. |
| Geriatric use | No specific dose adjustment required, but monitor renal function and adjust accordingly per renal adjustment guidelines. |
| 1st trimester | Contraindicated due to risk of teratogenicity (pseudoephedrine isomers) |
| 2nd trimester | Contraindicated due to risk of fetal tachycardia and uterine vasoconstriction |
| 3rd trimester | Contraindicated due to risk of premature labor and neonatal irritability |
Clinical note
Comprehensive clinical and safety monograph for MYFED (MYFED).
| Placental transfer | Crosses placenta extensively; achieves fetal concentrations equal to maternal levels |
| Breastfeeding | Excreted into breast milk; may cause irritability and poor feeding in infants. Avoid in nursing mothers with hypertension or premature infants. |
| Lactation Rating | L3 (Moderately Safe) – use with caution |
| Teratogenic Risk | Category C: First trimester risk of major malformations not clearly increased; second and third trimester use associated with fetal tachycardia, premature closure of ductus arteriosus, and oligohydramnios. Avoid in third trimester. |
| Fetal Monitoring | Monitor maternal blood pressure and heart rate regularly. Fetal ultrasound for growth and amniotic fluid index if used in second half of pregnancy. Fetal heart rate monitoring after maternal dosing. |
| Fertility Effects | No conclusive evidence of impaired fertility in males or females. Animal studies show no significant reproductive toxicity at clinically relevant doses. |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to pseudoephedrine or any componentSevere hypertensionSevere coronary artery diseaseNarrow-angle glaucomaUrinary retentionConcomitant use of MAOIs or within 14 days
| Precautions | Use with caution in hypertension, coronary artery disease, hyperthyroidism, diabetes, prostatic hypertrophy, and glaucoma. Avoid in patients with severe or uncontrolled hypertension. Prolonged use may lead to rebound congestion. |
| Food/Dietary | Avoid high-tyramine foods (aged cheese, cured meats, fermented products) as pseudoephedrine may cause hypertensive crisis with MAOIs; do not use MYFED if you have taken an MAOI in the last 14 days. Grapefruit and grapefruit juice may increase anticholinergic effects. |
| Clinical Pearls | MYFED is a combination of pseudoephedrine (decongestant) and triprolidine (antihistamine). Avoid in patients with severe hypertension, coronary artery disease, or narrow-angle glaucoma. Use caution in elderly due to anticholinergic effects (confusion, urinary retention). May cause CNS stimulation or sedation; assess patient's response before driving. |
| Patient Advice | Take MYFED exactly as directed; do not exceed recommended dose due to risk of serious side effects. · Do not use with other products containing pseudoephedrine or other decongestants. · Avoid alcohol and sedatives as they may increase drowsiness. · Do not drive or operate machinery until you know how MYFED affects you. · Stop use and consult doctor if you experience fast, irregular heartbeat, severe dizziness, or difficulty urinating. |
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