Lipid soluble quaternary ammonium

This technique involves the extraction of the anion of an organic acid as its ion pair with a lipid soluble quaternary ammonium cation (in our case, this... 

Use. A solution of this oil-soluble quaternary ammonium salt in chloroform or ethyl acetate quantitatively extracts polar, anionic lipids such as steroid conjugates from aqueous solution by a process of anion exchange. 

Trospium chloride, a quaternary ammonium drug (Fig. 7.45), appears to be a substrate of P-gp, and it can be taken up by cells quicky [597]. The evidence for transmembrane diffusion appears substantial. The molecule is very soluble in water (>50 mg/mL), but not in lipids (9.2 pg/mL in mineral oil) the octanol-water log Kp is —1.22 [598]. The human intestinal absorption (HIA) is 11% the molecule is not metabolized. In cell intestinal patch uptake studies, trospium is absorbed from a... 

Quaternary ammonium compounds are less lipid-soluble and therefore tend to cause fewer central atropine-like side-effects, whereas peripheral side-effects... 

The oximes contain a quaternary ammonium group that contributes to their acidity and their strong binding to the inhibited enzyme. This appears to be a key structural element in known reactivators, but it tends to make them poorly soluble in lipids. Practically, this means that the drugs are slowly absorbed from the gastrointestinal tract, have difficulty entering the brain, do not easily enter hepatic cells to be biotransformed, and are not reabsorbed from the renal tubular urine. 

Glasses exist that fnnction as selective electrodes for many different monovalent and some divalent cations. Alternatively, a hydrophobic membrane can be made semiper-meable if a hydrophobic molecnle called an ionophore that selectively binds an ion is dissolved in it. The selectivity of the membrane is determined by the structnre of the ionophore. Some ionophores are natnral products, such as gramicidin, which is highly specific for K+, whereas others such as crown ethers and cryptands are synthetic. Ions such as, 1, Br, and N03 can be detected using quaternary ammonium cationic surfactants as a lipid-soluble counterion. ISEs are generally sensitive in the 10 to 10 M range, but are not perfectly selective. The most typical membrane material used in ISEs is polyvinyl chloride plasticized with dialkylsebacate or other hydrophobic chemicals. 

The interaction of dmgs in the charged form with other ions to form absorbable species with a high lipid solubility is a possible explanation for the ability of molecules such as quaternary ammonium compounds, ionised under all pH conditions, to be usefully absorbed. The origin of the ions which pair with dmg ions is not clear, but there is evidence that ion-pair formation will aid absorption. 

Orally administered corticosteroids are effective in the treatment of chronic bronchial asthma. The inhalation route has been widely used in attempts to avoid systemic side-effects, such as adrenal suppression, but evidence suggests that inhaled steroids are absorbed systemically to a significant extent. The respiratory tract epithelium has permeability characteristics similar to those of the classical biological membrane, so lipid-soluble compounds are absorbed more rapidly than lipid-insoluble molecules. Cortisone, hydrocortisone and dexamethasone are absorbed rapidly by a nonsaturable diffusion process from the lung, the half-time of absorption being of the order of 1-1.7 min. Quaternary ammonium compounds, hippurates and mannitol have absorption half-times, in contrast, of between 45 and 70 min. 

Antimuscarinics having a quaternary ammonium group are incompletely absorbed from the gut since these are completely ionized. The tertiary amine antimuscarinics are readily absorbed from the gut. The presence of food may reduce absorption. Quaternary ammonium antimuscarinics exhibit poor lipid solubility, do not cross the blood-brain barrier, and thus exhibit minimal central nervous system (CNS) effects. Also due to their poor lipid solubility they do not penetrate the eye and are unlikely to appear in the milk. Atropine and other tertiary amines are capable of crossing the CNS. Atropine is capable of crossing the placenta and has been stated to distribute into milk in small quantities. It is oxidized primarily in the liver. Atropine is apparently metabolized in the liver to tropic acid, tropine, and possibly esters of tropic acid and glucuronide conjugate. 

Cerilpyridiniutii chloride is the 1-hexadecylpyridinium chloride (USP/NF-. Eur.Ph.-, BP-, and Martindate-compliant). Lin et al. (33) compared the primaiy ocular and dermal irritations of several quaternary ammonium compounds. They concluded that the irritancy of these compounds is likely to be related to their solubility in addition to their cationic characteristics. Only celylpyridinium chloride is very soluble in both lipids and w er. It appears that not all of the quaternary ammonium compounds studied are irritant, but celylpyridinium chloride was severely irritating to the skin of the test animal. In a recent work. Green et al. (34) confirmed that ophthalmic medications containing celylpyridinium chloride are potentially hazardous to the comeal endothelium. 

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