Routes, Dosage Forms, and Average Onsets of Action

I am frequently asked by healthcare professionals (i.e. physicians, physician assistants, nurses, nurse practitioners, pharmacists) about Routes, Dosage Forms, and the Average Onsets of Action. When it comes to designing and engineering a personal medicated product for a patient, choosing the correct dosage form and route is critical: age, weight, hospice, pediatric, women, men, etc. — each variable is taken into consideration.

Intravenous (IV)
Dosage Form: Aqueous solutions, emulsions
Onset of Action: Within 60 seconds
Intramuscular (IM)
Dosage Form: Aqueous solutions, oily solutions, suspensions
Onset of Action: 15 to 30 minutes for aqueous solutions
Subcutaneous (Sub-Q)
Dosage Form: Aqueous solutions, suspensions, implants
Onset of Action: 15 to 60 minutes for aqueous solutions
Sublingual
Dosage Form: Tablets, solutions, aerosols
Onset of Action: 1 to 3 minutes
Buccal
Dosage Form: Tablets, lozenges (troches), chewing gum
Onset of Action: 2 to 3 minutes
Oral
Dosage Form: Tablets, solutions, suspensions
Onset of Action: 30 to 60 minutes for immediate release (IR) dosage forms
Rectal
Dosage Form: Suppositories, ointment, creams, solutions, suspensions, foams
Onset of Action: 30 to 60 minutes
Vaginal
Dosage Form: Inserts, creams, gels, tablets, rings
Onset of Action: Slow for systemic effects
Skin (transdermal)
Dosage Form: Patches, ointments, gels
Onset of Action: 1 to 4 hours
Nose
Dosage Form: Aerosolized solutions or suspensions
Onset of Action: Within 10 minutes
Lung
Dosage Form: Aerosolized solutions, suspensions, or powders
Onset of Action: Within 5 minutes

Adapted from Chambers Fox S. Remington Education: Pharmaceutics. Fairford, UK; Pharmaceutical Press: 2014.