Comparing doses for the Spiriva Handihaler and Spiriva Respimat is somewhat difficult since the active ingredient (tiotropium) is administered in different dosage forms.
The Spiriva Handihaler is a dry-powder inhaler. The amount of powder inhaled from the punctured capsule is 18 mcg (micrograms) of tiotropium. Spiriva Handihaler is only available in one strength (18 mcg).
The Spiriva Respimat delivers tiotropium as an aerosolized spray. It is available in two strengths:
- 1.25 mcg/actuation
- 2.5 mcg/actuation
Although the dose from Spiriva Respimat is clearly less than that of the Spiriva Handihaler, it is far better absorbed.
The prescribing information for Spiriva Respimat states the following in regard to getting a comparable dose to the Handihaler:
"A dedicated pharmacokinetic study in patients with COPD evaluating once-daily tiotropium delivered from the RESPIMAT inhaler (5 mcg) and as inhalation powder (18 mcg) from the HandiHaler resulted in a similar systemic exposure between the two products."
So, for the Spiriva Respimat, a dose of 5mcg (two inhalations of the 2.5 mcg strength) is essentially equal to a18 mcg dose from the Spiriva Handihaler.
From Handihaler To Respimat
In regard to your question specifically, you are correct that two inhalations of Spiriva Respimat 1.25 mcg (a total dose of 2.5 mcg), is not considered equivalent to one 18 mcg dose from the Handihaler.
As discussed in the section above, the equivalent dose (in terms of systemic exposure to tiotropium) to one 18 mcg Handihaler dose is two inhalations of Spiriva Respimat 2.5 mcg (a total dose of 5 mcg).
While the dose you are being switched to (two inhalations of1.25 mcg) is less than what you were using with the Handihaler, it is important to consider what you are using it for, the treatment of asthma or COPD. This is important because the FDA-approved dose is different for each condition.
The following are the FDA-approved doses for Spiriva Respimat:
- Asthma: 2 inhalations of Spiriva Respimat 1.25 mcg once-daily (total dose of 2.5 mcg)
- COPD: 2 inhalations of Spiriva Respimat 2.5 mcg once-daily (total dose of 5 mcg)
If you are using Spiriva Respimat for asthma, your doctor has you on the correct dose per the FDA-approved indications (2 inhalations of the 1.25 mcg strength once-daily).
If you are concerned you are not on the correct dose of Spiriva Respimat (especially since it is lower than your previous Handihaler dose), be sure to talk with your doctor about it. Perhaps it was a mistake or they have a rationale for the dose they prescribed.
If you are interested in learning more about the difference between Spiriva Handihaler and Spiriva Respimat, we wrote an article on that very subject, which can be found here.
SummaryTwo inhalations of Spiriva Respimat (tiotropium) 2.5 mcg (5 mcg total dose) produces similar systemic concentrations to Spiriva Handihaler 18 mcg.