In vivo photodegradation of chlorpromazine

Chemical Synthetic Platform for Chlorpromazine Oligomers That Were Reported as Photo-degradation Products of Chlorpromazine

A synthetic platform for chlorpromazine (CPZ) oligomers, which could be generated via photo-reaction of CPZ, is essential to promote their biological and structural studies. In this paper, the first synthetic platform for CPZ oligomers is described. A photo-irradiation experiment of CPZ to confirm whether the structure of the CPZ dimer generated by the photo-irradiation was identical to that prepared by our synthetic method is also reported.

ESR studies on the effect of cholesterol on chlorpromazine interaction with saturated and unsaturated liposome membranes

In this study, the effects of chlorpromazine (CPZ) on lipid order and motion in saturated (DMPC, DMPG) and unsaturated (SOPC) liposome membranes were investigated by electron spin resonance (ESR) spin labeling technique. We have shown that above the main phase transition temperature of membrane lipids (T(M)), CPZ slightly increases lipid order in membranes without cholesterol, whereas below T(M) it has a strong opposite effect. Addition of 30 mol% of cholesterol into DMPC and SOPC membranes changes significantly the CPZ effects both above and below T(M). Additionally, above T(M), the ordering effect of CPZ on pure SOPC membrane is stronger at pH 7.4 than at pH 9.0, whereas below T(M), as well as in the presence of cholesterol, pH does not seem to play a role in CPZ effect on both membranes. Because of the strong influence of membrane composition on CPZ effect on membranes, the use of cholesterol as a marker of CPZ photosensitized reactions has been discussed.

Isolation and structural elucidation of degradation products of alprazolam: photostability studies of alprazolam tablets

Accelerated thermal, hydrolytic, and photochemical degradations of alprazolam were performed under several reaction conditions. The stress studies revealed the photolability of the drug as the most adverse stability factor; the main photodegradation products were isolated and properly characterized as: triazolaminoquinoleine; 5-chloro-[5"-methyl-4H-1,2,4-triazol-4-yl]benzophenone, and 1-methyl-6-phenyl-4H-s-triazo-[4,3-alpha][1,4]benzodiazepinone. Accelerated pH-dependent studies show that the photoinstability increases as the pH decreases; at pH 9.0, photodegradation does not occur, therefore, the photochemical degradation of alprazolam was performed in buffered solutions at pH 2.0 and 3.6. The higher rate of reaction was observed at pH = 2.0; consequently, acidic conditions should be avoided and appropriate light protection is recommended during the drug-development process, storage, and handling. The main degradation route for alprazolam tablets is also photochemical.

Chlorpromazine-induced increase in dipalmitoylphosphatidylserine surface area in monolayers at room temperature

The Langmuir technique revealed that the surface area of acidic glycerophospholipids (dipalmitoylphosphatidylserine, -glycerol, and dipalmitoylphosphatidic acid) in monolayers increased dramatically when micromolar concentrations of the antipsychotic drug chlorpromazine (CPZ) were present in the subphase. Monolayers of neutral glycerophospholipids (dipalmitoylphosphatidylcholine and -ethanolamine) did not show such a large effect with CPZ. Compared to CPZ, millimolar concentrations of the monovalent cations Li+, K+, Na+, Rb+, and Cs+ did not appear to influence the dipalmitoylphosphatidylserine monolayer, suggesting that the effect of CPZ, a monovalent cationic amphophile, was due to an interaction with the acyl chains of the lipids. In addition, the effect of CPZ was reduced by 150 mM Na+, suggesting that the sodium cations might screen the negatively charged headgroups from an electrostatic interaction with the positively charged drug molecule. Two CPZ analogs, chlorpromazine sulfoxide and CPZ with 2 carbons in the side chain, were also studied. These observations suggest that part of the biological effects of CPZ, being antipsychotic and/or side effects, may be due to CPZ's action on the acidic glycerophospholipids in nerve cell membranes.

Chlorpromazine, a candidate drug for photopheresis

Photopheresis is a therapy for several T-cell-mediated disorders, aiming at a specific immune response against the pathogenic clone of T cells involved. With photopheresis, a mixture of patients' buffy coat and plasma, which contains 8-methoxypsoralen (8-MOP), is diluted with saline and exposed to ultraviolet A radiation (UVA). After the irradiation the treated fraction is reinfused. To improve this therapy and to broaden its scope, insight into the underlying mechanism is essential. Regarding the mechanism, photomodification of biomacromolecules is considered to be crucial in photopheresis. Up to the present, much emphasis has been put on the photobinding to DNA. However, photobinding to proteins can also play an important role in photopheresis, because much of the communication between the various parts of the immune system occurs via protein-protein interactions. In this study we compared the activity of 8-MOP and chlorpromazine (CPZ) in our animal model for photopheresis based on contact hypersensitivity. It proved that CPZ was able to induce specific immune suppression, just as 8-MOP. In addition, photobinding of CPZ and 8-MOP to lymphocytes was determined. It was shown that under conditions relevant for photopheresis the photobinding to DNA of 8-MOP exceeds that of CPZ by a factor of 22. This holds for both rat and human lymphocytes. With the photobinding to proteins it is just the other way round; the photobinding of CPZ exceeded that of 8-MOP by a factor of 23 for rat lymphocytes and 28 for human lymphocytes. This study proves that CPZ is an interesting candidate drug for photopheresis and shows that not only photobinding to DNA is crucial in photopheresis, but photobinding to proteins is important as well.

Horseradish peroxidase-catalyzed sulfoxidation of promethazine and properties of promethazine sulfoxide

Promethazine sulfoxide was obtained with a quantitative yield in a horse radish peroxidase-catalyzed reaction of promethazine and hydrogen peroxide and was also prepared by direct chemical synthesis. The enzymatic sulfoxidation of promethazine was studied in vitro as a function of pH, promethazine, and hydrogen peroxide concentration. Promethazine sulfoxide inhibits with an apparent K(i) of 59.7 microM at pH 5.5 the enzymatic reaction, followed spectrophotometrically, polarographically, potentiometrically, and luminometrically. The reaction was also inhibited by ascorbic acid (K(i) 26.8 microM) and glutathione (K(i) 41.8 microM). The spectrophotometric techniques employed, together with ESR spectrometry, allowed the identification of at least three radical species formed in the course of the reaction. Promethazine sulfoxide is devoid of the antioxidant effect exhibited by promethazine on rat brain synaptosomes. The sulfoxide also lacks photosensitizing action, while retaining the neuroleptic effect of the parent compound.

Photodegradation of some quinolones used as antimicrobial therapeutics

The photostability of the fluoroquinolones ciprofloxacin (CPX), ofloxacin (OFX), and fleroxacin (FLX) toward ultraviolet irradiation (UVA) and room light was investigated in dilute aqueous solutions. A series of photoproducts was observed by high-performance liquid chromatography (HPLC) for all three drugs. As little as 1 h of exposure to room light was enough for the formation of detectable amounts of CPX photoproducts. The major CPX photoproduct was characterized as a dimer by liquid secondary ion mass spectrometry, but its structure was not determined. Since irradiation of CPX results (as cited in ref/11) in a loss of antibacterial activity and since all substances, parent drugs as well as their photoproducts, are potential candidates for undesired drug effects, quinolone drugs should be strictly protected from all light during storage and administration.

UV-radiation protecting efficacy of thiols, studied with UVA-induced binding of 8-MOP and CPZ to rat epidermal biomacromolecules in vivo

The following topically-applied thiols were investigated with regard to their possible UV-radiation protective properties: captopril, cysteamine, ergothioneine, mesna, mercaptopropionylglycine, N-acetyl-cysteine and penicillamine. As a measure for protection the inhibition of in vivo irreversible photobinding of the labelled phototoxic drugs chlorpromazine (CPZ) and 8-methoxypsoralen (8-MOP) to rat epidermal biomacromolecules was used. Ergothioneine, mesna and penicillamine did not show any effect; probably, as a result of their charge they are not able to enter the stratum corneum. Captopril, cysteamine, mercaptopropionylglycine and N-acetylcysteine showed a considerable inhibition of CPZ and 8-MOP photobinding. Captopril and N-acetylcysteine were clearly the most potent whereas cysteamine was the least effective. Captopril, mercaptopropionylglycine and N-acetylcysteine appeared to have a wider action range and to be a more effective protector than dl-alpha-tocopherol and di-butyl-hydroxytoluene. Cysteamine and mercaptopropionylglycine were only capable of protecting the stratum corneum. Captopril and N-acetylcysteine on the other hand showed an additional dose-dependent inhibition of photobinding to the viable epidermis. Gradually with increasing time after application, the protecting efficacy with regard to the viable layer of the epidermis decreased; the duration of protection depending on the dose.

Thiols as potential UV radiation protectors: an in vitro study

The following thiols were investigated with regard to their possible UV-radiation protective properties: captopril, cysteamine, ergothioneine, mesna, mercaptopropionylglycine, N-acetylcysteine, and penicillamine. As a measure for protection, the inhibition of in vitro irreversible photobinding of the labeled phototoxic drugs chlorpromazine (CPZ) and 8-methoxypsoralen (8-MOP) to protein and DNA was used. Besides photobinding to biomacromolecules, the photodegradation of CPZ and the formation of promazine (PZH) and hydroxypromazine (PZOH) were measured as well. Because of the H-atom and electron donating capacity of the thiols, the ratio [PZOH]/[PZH] was expected to be decreased and the photodegradation of CPZ was expected to be higher in the presence of thiols. Maximum inhibition of CPZ photobinding ranged for the different thiols between 21-100% (DNA) and 17-87% (human serum albumin). All thiols enhanced the photodegradation of CPZ (19-84%) and inhibited the ratio [PZOH]/[PZH] (90-97%). 8-MOP photobinding to human serum albumin was also clearly inhibited (75-96%), but remarkably less to DNA (2-41%). This study indicates that thiols are able to cope with a variety of reactive species. Scavenging of radicals, quenching of singlet molecular oxygen species and reaction with excited states seem to be essential mechanisms involved with this process.

Photobinding of 8-methoxypsoralen, 4,6,4'-trimethylangelicin and chlorpromazine to Wistar rat epidermal biomacromolecules in vivo

Photoinduced binding of drugs to endogenous biomacromolecules may cause both toxic and therapeutic effects. For example, photobinding of certain phenothiazines to biomolecules possibly underlies their phototoxic and photoallergic potential, whereas photobinding of furocoumarins to epidermal DNA is held responsible for their advantageous effects in the photochemotherapy of psoriasis. Usually, the in vitro photobinding of drugs is investigated. However, under in vivo conditions, the metabolism and distribution of the drug and the light absorption by endogenous compounds will significantly affect the photobinding of drugs to biomolecules. Therefore, in the present study, the photobinding of 8-methoxypsoralen (8-MOP), 4,6,4'-trimethylangelicin (TMA) (two therapeutically used furocoumarins) and chlorpromazine (CPZ) (a member of the phenothiazines) was investigated in vivo. The compounds were applied topically on the shaven skin of Wistar rats; one group was exposed to UVA and the other was kept in a dimly lit environment. Immediately, and at certain time intervals after UVA exposure, members of the two groups were sacrificed. By separating epidermal lipids, DNA/RNA and proteins by a selective extraction method, irreversible binding of 8-MOP, TMA or CPZ to each of these biomacromolecules was determined. In contrast with in vitro experiments, photobinding of CPZ to epidermal DNA/RNA was not found in vivo; apparently the bioavailability in the nucleus is very low. Compared with TMA, 8-MOP was observed to bind more extensively to epidermal DNA/RNA (again in contrast with findings from in vitro experiments) and proteins, but less extensively to lipids. The rates of removal of photobound 8-MOP and TMA were comparable. Photobound CPZ was more slowly removed from epidermal proteins and lipids than the furocoumarins. The observed in vivo photobinding is discussed with respect to the UVA-induced (side) effects of these drugs.

(Systemic) phototoxicity of drugs and other xenobiotics

Xenobiotics extensively used in drugs, cosmetics, food and agricultural chemicals can produce adverse biological effects. These toxic effects are separated into classes, e.g. hepatotoxicity, genotoxicity and neurotoxicity. Skin allergy, part of immunotoxicity, is also a subdivision of toxicology. When light is an essential condition for toxicity, the xenobiotic is called phototoxic. Thus it fits into the logic of toxicology that photoallergic compounds are a subdivision of phototoxic compounds. Phototoxicons as a group do not differ from the group of phototherapeutics with regard to their eventual biological effects. The primary photoreactions, secondary molecular processes, biomolecules involved and cellular and tissue damage are similar. The difference between the two groups is in the appreciation of the photobiological effects: adverse vs. desired. The aim of research is to determine the part of the molecular structure which makes a given compound phototoxic. With that knowledge the structure of the phototoxicon can be changed. This can result in a derivative which still has the desired properties of the parent compound, but is no longer phototoxic. This aim can be reached by combining data from both in vitro and in vivo research. The variety and number of phototoxic compounds is large. This, together with the limited research effort devoted to this subject so far, means that for most phototoxic xenobiotics a relationship between structure and in vivo photoreactivity is not available. In this review, emphasis is placed on xenobiotics whose in vitro and in vivo photochemistry have been studied. Furthermore, possible phototoxic effects which do not concern the skin but involve inner organs (systemic effects) are considered. References in this review mostly concern investigations over the last 10 years. For older literature or for additional information, references to other reviews are given. Important groups of phototoxic xenobiotics not dealt with in this article were already sufficiently covered in the reviews referred to.