Pharmacokinetic studies of drug absorption have been hindered by the need to separate pulmonary absorption from that occurring in the gastrointestinal tract. Drug will be swallowed following oropharyngeal deposition when the aerosol is fired, and the dose administered by this route may be greater than that entering the lungs. In addition drug impacting on the upper airways may be cleared by the mucociliary escalator and swallowed at a later time. Pulmonary absorption is expected to be fast since the drug arrives rapidly at the target site, compared to the delay involved in transit through the gastrointestinal tract. Studies involving salbutamol administered from a pressurized aerosol showed that peak plasma levels were reached 3-5 hours after dosing, but in this case the peak plasma level was probably related to the gastrointestinal absorption of the swallowed part of the dose36. Another study involving terbutaline indicated that after inhalation, the peak plasma level was reached within 30 to 60 minutes37. In this experiment ingested charcoal was used to prevent absorption from the gastrointestinal tract; without charcoal the peak plasma level was reached at 1-6 hours. This confirms that absorption from the airways is more rapid than from the gut. However, it may be possible that the peak plasma concentration results from absorption from the oral and pharyngeal mucosa for some drugs.

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Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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