Dosing and uses of Midrin (isometheptene/dichloralphenazone/acetaminophen)
Adult dosage forms and strengths
isometheptene/dichloralphenazone/acetaminophen
capsule: Schedule IV
- 65mg/100mg/325mg
Migraine Headache
2 capsules PO at onset of headache, then 1 capsule PO q1hr until headache relieved up to a cumulative dose of 5 capsules/12 hr
Tension Headache
1-2 capsules PO q4hr; not to exceed 8 capsules/24 hr
Pediatric dosage forms and strengths
Safety and efficacy not established
Midrin (isometheptene/dichloralphenazone/acetaminophen) adverse (side) effects
Frequency not defined
Rash
Transient dizziness
Warnings
Contraindications
Hypersensitivity
Hepatitis or severe hepatic/renal impairment
Glaucoma
Severe renal impairment
Hypertension
Heart disease
Hepatic impairment
Within 14 days of MAO inhibitors
Cautions
Risk of hepatotoxicity higher in alcoholics, or with use of more than one acetaminophen-containing product
Acetaminophen: Risk for rare, but serious skin reactions that can be fatal; these reactions include Stevens-Johnson Syndrome (SJS), toxic epidermal necrolysis (TEN), and acute generalized exanthematous pustulosis (AGEP); symptoms may include skin redness, blisters and rash
G6PD deficiency
May cause sedation; avoid driving car or operating machinery
May increase respiratory depressant effects; caution with head injury, COPD, or other conditions with decreased respiratory drive
Controlled substance (dichloralphenazone); may cause tolerance/dependence
Caution in cardiovascular disease, hepatic impairment, G6PD deficiency
Pregnancy and lactation
Pregnancy category: C
Lactation: Excreted in breast milk; caution advised
Dichloralphenazone: prodrug of chloral hydrate and phenazone; trichloroethanol (active metabolite of chloral hydrate), acetaminophen, and phenazine are excreted in breast milk
According to the American Academy of Pediatrics, chloral hydrate and acetaminophen are compatible with breastfeeding
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Midrin (isometheptene/dichloralphenazone/acetaminophen)
Mechanism of action
Isometheptene: Elicits sympathomimetic effect; constricts dilated cerebral/cranial arterioles
Dichloralphenazone: Elicits mild sedative effect; reduces emotional response to painful stimulus
Acetaminophen: Inhibitis prostaglandin sythesis in CNS and may block peripheral pain impulse generation; acts on hypothalamus to antipyresis
