Phenolic groups, drugs containing

Nickel and Weber [30] reported aqueous titrations of carboxylic acids, phenols, acidic drugs containing NH groups, cationic acids (ammonium salts) in dimethyl-formamide solution against 0.1 M potassium hydroxide aqueous solution as the... 

Huck WC, Stecher G, Scherz H and Bonn G. 2005. Analysis of drugs, natural and bioactive compounds containing phenolic groups by capillary electrophoresis coupled to mass spectrometry. Electrophoresis 26(7-8) 1319-1333. 

Partition coefficient ofun-ionised compound at acidic pH Octanol/water ca 631. Other drugs containing phenolic ester group metipranolol, vitamin E, benorylate, dipivefrin. 

A number of common drugs contain the phenol functional group. These include paracetamol (pFCa 9.5), morphine (pKa 9.9) and levothyroxine (thyroxine) (pKa 10). Since these phenolic drugs are 50% ionised when the pH equals their pKa, it follows from the rule of thumb introduced in Chapter 1 that they will only ionise to approximately 1% at the pH of blood (7.4). See Figure 3.6. 

Drugs containing phenolic groups include the analgesics morphine (and related opiates) and paracetamol as well as the bronchodilator salbutamol, widely used in the treatment of acute asthma. See Figure 8.9. 

Drugs that contain two phenolic groups, such as adrenaline (epinephrine) and other catecholamines such as noradrenaline (norepinephrine) and isoprenaline are particularly susceptible to oxidation and have to be formulated at acidic pH. All of these compounds are white crystalline solids that darken on exposure to air. Adrenaline forms the red coloured compound adrenochrome on oxidation (Figure 8.10), which can further polymerise to give black compounds similar in structure to melanin, the natural skin pigment. Injections of adrenaline that develop a pink colour, or that contain crystals of black compound, should not be used for this reason. Adrenaline for injection is formulated as the acid tartrate... 

Derivatization of drugs containing alcoholic or phenolic hydroxy groups... 

Chemical formulations mainly deal with the direct irritating properties of drugs containing phenolic or acidic groups. For example, to eliminate gastric irritation produced... 

Modifying drug metabolism and excretion 174 Drugs containing phenolic groups 174... 

Terpenes are polymers of the 5-carbon compound isoprene (Figure 1.12) and, as such, generally display properties similar to those of hydrocarbons. Terpenoids are substituted terpenes (i.e. contain additional chemical groups, such as an alcohol, phenols, aldehydes, ketones, etc.). Only a few such substances could be regarded as true drugs. Terpenes, such as limonene, menthol and camphor, form components of various essential oils with pseudo-pharmaceutical uses. A number of these molecules, however, exhibit anti-tumour activity, of which taxol is by far the most important. 

Because most drugs exist in a reduced form, there may be an increased instability when the solution is consistently introduced into an atmosphere of 20% oxygen. The pH of the solution may effect the oxidation of phenolic and sulfhydryl group containing drugs because it is principally the ionized form of these drugs that participate in the oxidation (11). For example, epinephrine is only slowly oxidized at pH < 4 but rapidly degrades under alkaline pH conditions. 

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