Drug Name Citalopram

It is stored instead of NE, but is unable to mimic the functions of the latter. In addition, it stabilizes the axonal membrane, thereby impeding the propagation of impulses into the sympathetic nerve terminals. Storage and release of epinephrine from the adrenal medulla are not affected, owing to the absence of a re-uptake process.
Following its uptake into the body, the drug is distributed in the blood (1) and through it to the various tissues of the body. Distribution may be restricted to the extracellular space (plasma volume plus interstitial space) (2) or may also extend into the intracellular space (3).

 

The central seven-membered ring of the TCAs imposes a 120° angle between the two flanking aromatic rings, in contradistinction to the flat ring system present in phenothiazine type neuroleptics (p. 237). The side chain nitrogen is predominantly protonated at physiological pH.
The tendency for the drug to leave the drug vehicle (V) is higher the more the drug and vehicle differ in lipophilicity (high tendency: hydrophilic D and lipophilic V, and vice versa). Because the skin represents a closed lipophilic barrier, only lipophilic drugs are absorbed. Hydrophilic drugs fail even to penetrate the outer skin when applied in a lipophilic vehicle.