The lungs perform several metabolic functions including
gas exchange
, conversion of angiotensin I to angiotensin II by angiotensin converting enzyme (ACE), inactivation of vasoactive substances, and protein synthesis. Angiotensin converting enzyme is found on the surface of capillary endothelial cells in the lungs.
What drugs are metabolised in the lungs?
Propofol
can be metabolized in the lung but this probably does not contribute significantly to total body metabolism. Other drugs that are biotransformed or metabolized include budesonide, ciclesonide, salmeterol, fluticasone, and theophylline.
Do the lungs metabolize drugs?
The
lungs possess many xenobiotic metabolizing enzymes
which influence the pharmacokinetics and safety of inhaled medicines. Anticipating metabolism in the lungs provides an opportunity to optimize new inhaled medicines and overcome challenges in their development.
How are drugs absorbed in the lungs?
Drug particles deposited in the conducting airways are primarily removed through mucociliary clearance and, to a lesser extent, are absorbed
through the airway epithelium into the blood or lymphatic system
. Ciliated epithelium extends from the trachea to the terminal bronchioles.
Where in the body are most drugs metabolized?
Most drugs must pass through
the liver
, which is the primary site for drug metabolism. Once in the liver, enzymes convert prodrugs to active metabolites or convert active drugs to inactive forms.
Is ACE produced in the lungs?
ACE, angiotensin I and angiotensin II are part of the renin-angiotensin system (RAS), which controls blood pressure by regulating the volume of fluids in the body. ACE is
secreted in the lungs and kidneys
by cells in the endothelium (inner layer) of blood vessels.
Do lungs filter clots?
The
lung is ideally positioned to filter out particulate matter such as
clots, fibrin clumps, and other endogenous and exogenous materials from entering the systemic circulation. This plays an important role in preventing ischaemia or even infarction to vital organs.
Can proteins be inhaled?
In principle, inhalation delivery of proteins offers an
attractive
, noninvasive alternative to injections and other modes of administration; lungs have a large surface area, are quite tolerant of foreign substances, are much more permeable than gastrointestinal and nasal mucosa or skin, and contain protease inhibitors …
How do inhaled drugs enter the bloodstream?
1. Inhalation (including smoking)—
Vapor or smoke goes into the lungs
to be absorbed into the bloodstream as rapidly as it would if it were injected. Smoking produces an extremely rapid high, and effects dissipate quickly.
What is pulmonary drug delivery system?
Pulmonary drug delivery is
a form of drug targeting
, whether to the site of action in the lungs for topically acting drugs, or the site of absorption for systemically acting drugs.
What happens if a drug is not metabolized?
If your body metabolizes a drug too slowly,
it stays active longer
, and may be associated with side effects. Because of this, your doctor may characterize you as being one of four metabolizer types, with respect to a specific enzyme. Poor metabolizers have significantly reduced or non-functional enzyme activity.
How are most drugs eliminated from the body?
Most drugs, particularly water-soluble drugs and their metabolites, are eliminated largely by
the kidneys in urine
. Therefore, drug dosing depends largely on kidney function. Some drugs are eliminated by excretion in the bile (a greenish yellow fluid secreted by the liver and stored in the gallbladder).
What is the primary site of drug absorption in the body?
The small intestine
has the largest surface area for drug absorption in the GI tract, and its membranes are more permeable than those in the stomach.
What cells in the lungs produce ACE?
Whereas ACE is detectable in the entire capillary network of the alveoli in the human lung, ACE2 is primarily produced in
club cells
What does ACE2 do in the lungs?
In addition to its protective role in the cardiovascular system, ACE2 has a direct protective role in
alveolar epithelial cells
. In the lungs ACE2 has numerous physiological functions, most of which are protective against lung injury.
Why do ACE inhibitors cause cough?
ACE inhibition
increases the cough reflex
. The mechanisms underlying ACE inhibitor-induced cough are probably linked to suppression of kininase II activity, which may be followed by an accumulation of kinins, substance P and prostaglandins.
