Chloroquine, quinine, procaine, quinidine, tricyclic antidepressants, and methylxanthines as prostaglandin agonists and antagonists

The associations between caffeine treatment and common preterm morbidities: a retrospective cohort analysis

Introduction

Caffeine is one of the most used drugs in the neonatal intensive care units (NICUs). It is widely regarded as beneficial in preventing many morbidities by reducing apnea of prematurity and improving respiratory functions.

Methods

Premature infants with gestational ages >25 and <32 weeks who were hospitalized in the NICU between 2008 and 2013 and survived up to discharge were retrospectively analyzed. Infants treated with prophylactic caffeine were compared with historical controls born in 2008 and did not receive caffeine treatment. Maternal and neonatal characteristics and common neonatal morbidities were recorded.

Results

A total of 475 patients were analyzed. The patients receiving caffeine were classified as Group 1 (n = 355), and the patients not receiving caffeine were classified as Group 2 (n = 120). Despite the higher incidence of respiratory distress syndrome requiring surfactant therapy and a longer duration of respiratory support in Group 2, the rates of bronchopulmonary dysplasia (BPD) and most other common morbidities were quite comparable. The frequency of apnea was statistically lower in the group that received caffeine prophylaxis (p < 0.01).

Conclusion

In this retrospective cohort analysis, we found that caffeine prophylaxis significantly decreased apnea attacks however does not prevent respiratory morbidity such as BPD.

Pharmacotherapy in Bronchopulmonary Dysplasia: What Is the Evidence?

Bronchopulmonary Dysplasia (BPD) is a multifactorial disease affecting over 35% of extremely preterm infants born each year. Despite the advances made in understanding the pathogenesis of this disease over the last five decades, BPD remains one of the major causes of morbidity and mortality in this population, and the incidence of the disease increases with decreasing gestational age. As inflammation is one of the key drivers in the pathogenesis, it has been targeted by majority of pharmacological and non-pharmacological methods to prevent BPD. Most extremely premature infants receive a myriad of medications during their stay in the neonatal intensive care unit in an effort to prevent or manage BPD, with corticosteroids, caffeine, and diuretics being the most commonly used medications. However, there is no consensus regarding their use and benefits in this population. This review summarizes the available literature regarding these medications and aims to provide neonatologists and neonatal providers with evidence-based recommendations.

What is bronchopulmonary dysplasia and does caffeine prevent it?

Bronchopulmonary dysplasia (BPD) is among the most severe complications of very premature birth. Clinical and laboratory studies indicate that lung immaturity, inflammatory lung injury, and disordered lung repair are the primary mechanisms responsible for the development of BPD. Caffeine, initiated within the first 10 days after birth, is one of few drug therapies shown to significantly decrease the risk of BPD in very low birth weight infants. This benefit is likely derived, at least in part, from reduced exposure to positive airway pressure and supplemental oxygen with caffeine therapy. Additional cardiorespiratory benefits of caffeine that may contribute to the lower risk of BPD include less frequent treatment for a PDA, improved pulmonary mechanics, and direct effects on pulmonary inflammation, alveolarization, and angiogenesis. Routine administration of caffeine is indicated in the vast majority of very low birth weight infants. However, current preventative strategies including widespread use of caffeine do not avert BPD in all cases. As such, there is continued need for novel methods to further reduce the risk of BPD in very low birth weight infants.

Hydroxychloroquine in COVID-19 Patients: Pros and Cons

The pandemic of COVID-19, caused by SARS-CoV-2, has recently overwhelmed medical centers and paralyzed economies. The unparalleled public distress caused by this pandemic mandated an urgent quest for an effective approach to manage or treat this disease. Due to their well-established anti-infectious and anti-inflammatory properties, quinine derivatives have been sought as potential therapies for COVID-19. Indeed, these molecules were originally employed in the treatment and prophylaxis of malaria, and later in the management of various autoimmune rheumatic and dermatologic diseases. Initially, some promising results for the use of hydroxychloroquine (HCQ) in treating COVID-19 patients were reported by a few in vitro and in vivo studies. However, current evidence is not yet sufficiently solid to warrant its use as a therapy for this disease. Additionally, the therapeutic effects of HCQ are not without many side effects, which range from mild gastrointestinal effects to life-threatening cardiovascular and neurological effects. In this review, we explore the controversy associated with the repurposing of HCQ to manage or treat COVID-19, and we discuss the cellular and molecular mechanisms of action of HCQ.

Caffeine: an evidence-based success story in VLBW pharmacotherapy

Apnea of prematurity (AOP) is a common and pervasive problem in very low birth weight infants. Methylxanthines were reported >40 years ago to be an effective therapy and, by the early 2000s, caffeine had become the preferred methylxanthine because of its wide therapeutic index, excellent bioavailability, and longer half-life. A clinical trial to address unresolved questions and toxicity concerns, completed in 2004, confirmed significant benefits of caffeine therapy, including shorter duration of intubation and respiratory support, reduced incidence of chronic lung disease, decreased need for treatment of patent ductus arteriosus, reduced severity of retinopathy of prematurity, and improved motor and visual function. Cohort studies have now further delineated the benefits of initiation of therapy before 3 days postnatal age, and of higher maintenance doses to achieve incremental beneficial effects. This review summarizes the pivotal and in particular the most recent studies that have established the safety and efficacy of caffeine therapy for AOP and other respiratory and neurodevelopmental outcomes. Caffeine has a very favorable benefit-to-risk ratio, and has become one of the most prescribed and cost-effective pharmacotherapies in the NICU.

Shifting the boundaries for early caffeine initiation in neonatal practice: Results of a prospective, multicenter study on very preterm infants with respiratory distress syndrome

Background

There is growing evidence that supports the benefits of early use of caffeine in preterm neonates with RDS; however, no formal recommendations specifying the exact timing of therapy initiation have been provided.

Objectives

We compared neonatal outcomes in infants receiving early (initial dose on the 1st day of life) and late (initial dose on day 2+ of life) caffeine therapy.

Methods

Using data from a prospective, cohort study, we identified 986 infants ≤32 weeks’ gestation with RDS and assessed the timing of caffeine therapy initiation, need for ventilatory support, mortality and incidence of typical complications of prematurity. To adjust for baseline severity, the early and late caffeine groups were propensity score (PS) matched to 286 infants (1:1). Clinical outcomes were compared between the PS-matched groups.

Results

Early treatment with caffeine citrate was associated with a significantly reduced need for invasive ventilation (71.3% vs 83.2%; P = 0.0165) and total duration of mechanical ventilation (mean 5 ± 11.1 days vs 10.8 ± 14.6 days; P = 0.0000) and significantly lower odds of intraventricular hemorrhage (IVH) (OR 0.4827; 95% CI 0.2999–0.7787) and patent ductus arteriosus (PDA) (OR 0.5686; 95% CI 0.3395–0.9523). The incidence of bronchopulmonary dysplasia (BPD) (36.4% vs 45.8%) and rates of moderate and severe BPD were not significantly different between the two groups. The mortality rates were comparable between the two groups (8.6% vs 8.5%, P = ns)

Conclusion

Early caffeine initiation was associated with a decreased need for invasive ventilatory support and lower incidence of IVH and PDA.

Systematic review and meta-analysis of clinical outcomes of early caffeine therapy in preterm neonates

AIMS

This study evaluated the therapeutic outcomes of early versus late caffeine therapy in preterm neonates.

METHODS

We performed a systematic literature search in PubMed, Embase, CINAHL and CENTRAL from inception to 30 June 2016 to identify studies investigating the use of early caffeine therapy (initiated at less than 3 days of life) in preterm infants. Effect estimates were combined using random-effects meta-analysis. The primary outcomes for this study were bronchopulmonary dysplasia and mortality.

RESULTS

The initial search found 4066 citations, of which 14 studies enrolling a total of 64 438 participants were included. The time of initiation of early caffeine therapy varied from the first 2 h to 3 days postnatal. Early caffeine therapy reduced the risk of bronchopulmonary dysplasia in both cohort studies (RR: 0.80, 95% CI: 0.66 to 0.96) and randomized controlled trials (RR: 0.67, 95% CI: 0.56 to 0.81). In cohort studies, neonates treated early with caffeine also showed decreased risks of patent ductus arteriosus, brain injury, retinopathy of prematurity and postnatal steroid use. However, the mortality rate was increased.

CONCLUSIONS

The findings suggest that early caffeine therapy is associated with reduced incidence of bronchopulmonary dysplasia and may help decrease the burden of morbidities in preterm infants.

Hydroxychloroquine in patients with inflammatory and erosive osteoarthritis of the hands (OA TREAT): study protocol for a randomized controlled trial

Background

Osteoarthritis (OA) is a heterogeneous group of conditions with disturbed integrity of articular cartilage and changes in the underlying bone. The pathogenesis of OA is multifactorial and not just a disease of older people. Hydroxychloroquine (HCQ) is a disease-modifying anti-rheumatic drug (DMARD) typically used for the treatment of various rheumatic and dermatologic diseases. Three studies of HCQ in OA, including one abstract and one letter, are available and use a wide variety of outcome measures in small patient populations. Despite initial evidence for good efficacy of HCQ, there has been no randomized, double-blind, and placebo-controlled trial in a larger patient group. In the European League Against Rheumatism (EULAR), evidence-based recommendations for the management of hand OA, HCQ was not included as a therapeutic option because of the current lack of randomized clinical trials.

Methods/Design

OA TREAT is an investigator-initiated, multicenter, randomized, double-blind, placebo-controlled trial. A total of 510 subjects with inflammatory and erosive hand OA, according to the classification criteria of the American College of Rheumatology (ACR), with recent X-ray will be recruited across outpatient sites, hospitals and universities in Germany. Patients are randomized 1:1 to active treatment (HCQ 200 to 400 mg per day) or placebo for 52 weeks. Both groups receive standard therapy (non-steroidal anti-inflammatory drugs [NSAID], coxibs) for OA treatment, taken steadily two weeks before enrollment and continued further afterwards. If disease activity increases, the dose of NSAID/coxibs can be increased according to the drug recommendation. The co-primary clinical endpoints are the changes in Australian-Canadian OA Index (AUSCAN, German version) dimensions for pain and hand disability at week 52. The co-primary radiographic endpoint is the radiographic progression from baseline to week 52. A multiple endpoint test and analysis of covariance will be used to compare changes between groups. All analyses will be conducted on an intention-to-treat basis.

Discussion

The OA TREAT trial will examine the clinical and radiological efficacy and safety of HCQ as a treatment option for inflammatory and erosive OA over 12 months. OA TREAT focuses on erosive hand OA in contrast to other current studies on symptomatic hand OA, for example, HERO [Trials 14:64, 2013].

Trial registration

ISRCTN46445413, date of registration: 05-10-2011.

Pharmacology of Chloroquine and Hydroxychloroquine

The 4-aminoquinolines are weak bases that are completely absorbed from the gastrointestinal tract, sequestered in peripheral tissues, metabolized in the liver to pharmacologically active by-products, and excreted via the kidneys and the feces. The parent drugs and metabolites are excreted with a half-life of elimination of approximately 40 days. However, slow release from sequestered stores of the drugs means that after discontinuation, they continue to be released into the plasma for years. Correct dosing is based on the ideal body weight of the patient, which depends on height. The 4AQs diminish autoimmunity without compromising immunity to infections.

The postoperative analgesic efficacy of preperitoneal continuous wound infusion compared to epidural continuous infusion with local anesthetics after colorectal cancer surgery: a randomized controlled multicenter study

BACKGROUND

Open colorectal cancer (CRC) surgery induces severe and prolonged postoperative pain. The optimal method of postoperative analgesia in CRC surgery has not been established. We evaluated the efficacy of preperitoneal continuous wound infusion (CWI) of ropivacaine for postoperative analgesia after open CRC surgery in a multicenter randomized controlled trial.

METHODS

Candidates for open CRC surgery randomly received preperitoneal CWI analgesia or continuous epidural infusion (CEI) analgesia with ropivacaine 0.2% 10 mL/h for 48 hours after surgery. Fifty-three patients were allocated to each group. All patients received patient-controlled IV morphine analgesia.

RESULTS

Over the 72-hour period after the end of surgery, CWI analgesia was not inferior to CEI analgesia. The difference of the mean visual analog scale score between CEI and CWI patients was 1.89 (97.5% confidence interval = -0.42, 4.19) at rest and 2.76 (97.5% confidence interval = -2.28, 7.80) after coughing. Secondary end points, morphine consumption and rescue analgesia, did not differ between groups. Time to first flatus was 3.06 ± 0.77 days in the CWI group and 3.61 ± 1.41 days in the CEI group (P = 0.002). Time to first stool was shorter in the CWI than the CEI group (4.49 ± 0.99 vs 5.29 ± 1.62 days; P = 0.001). Mean time to hospital discharge was shorter in the CWI group than in the CEI group (7.4 ± 0.41 and 8.0 ± 0.38 days, respectively). More patients in the CWI group reported excellent quality of postoperative pain control (45.3% vs 7.6%). Quality of night sleep was better with CWI analgesia, particularly at the postoperative 72-hour evaluation (P = 0.009). Postoperative nausea and vomiting was significantly less frequent with CWI analgesia at 24 hours (P = 0.02), 48 hours (P = 0.01), and 72 hours (P = 0.007) after surgery evaluations.

CONCLUSIONS

Preperitoneal CWI analgesia with ropivacaine 0.2% continuous infusion at 10 mL/h during 48 hours after open CRC surgery provided effective postoperative pain relief not inferior to CEI analgesia.

Hydroxychloroquine: from malaria to autoimmunity

Quinine was first recognized as a potent antimalarial agent hundreds of years ago. Since then, the beneficial effects of quinine and its more advanced synthetic forms, chloroquine and hydroxychloroquine, have been increasingly recognized in a myriad of other diseases in addition to malaria. In recent years, antimalarials were shown to have various immunomodulatory effects, and currently have an established role in the management of rheumatic diseases, such as systemic lupus erythematosus and rheumatoid arthritis, skin diseases, and in the treatment of chronic Q fever. Lately, additional metabolic, cardiovascular, antithrombotic, and antineoplastic effects of antimalarials were shown. In this review, we discuss the known various immunomodulatory mechanisms of antimalarials and the current evidence for their beneficial effects in various diseases and in potential novel applications.

Hydroxychloroquine in systemic lupus erythematosus and rheumatoid arthritis and its safety in pregnancy

INTRODUCTION

The antimalarial drug hydroxychloroquine (HCQ) is widely used to treat various rheumatic diseases. Many autoimmune diseases occur in women of child-bearing age who may become pregnant while on therapy, which raises concerns regarding the teratogenicity of HCQ and its effect on the outcome of the pregnancy. There is a lack of data regarding the safety of HCQ during pregnancy.

AREAS COVERED

In this review, the authors attempt to identify relevant publications by searching MEDLINE, Cochrane database, Ovid-Currents Clinical Medicine, Ovid-Embase:Drugs and Pharmacology, EBSCO, Web of Science and SCOPUS using the search terms HCQ and/or pregnancy. A basis for the mechanism of action of HCQ is provided.

EXPERT OPINION

HCQ has been shown by numerous studies over the past 15 years to be efficacious in the treatment of autoimmune diseases, including systemic lupus erythematosus, discoid lupus erythematosus and rheumatoid arthritis. HCQ does not appear to be associated with any increased risk of congenital defects, spontaneous abortions, fetal death, prematurity or decreased numbers of live births in patients with autoimmune diseases. Therefore, in the author's opinion, HCQ is safe for the treatment of autoimmune diseases during pregnancy.

Intraperitoneal use of local anesthetic in laparoscopic cholecystectomy: systematic review and metaanalysis of randomized controlled trials

BACKGROUND/PURPOSE

With the advent of minimally invasive gallbladder surgery, and now with natural orifice techniques emerging, visceral nociception has been neglected as a cause of postoperative pain. A systematic review and metaanalysis was carried out to investigate the use of intraperitoneal local anesthetic (IPLA) in order to assess its role in laparoscopic cholecystectomy (LC). The aim of this systematic review was to appraise the clinical effects of this modality.

METHODS

Comprehensive searches were conducted independently without language restriction. Studies were identified from the following databases from inception to September 2009: Cochrane Central Register of Controlled Trials (CENTRAL/CCTR), Cochrane Library, Medline, PubMed, Excerpta Medica Database (EMBASE), and Cumulative Index to Nursing and Allied Health Literature (CINHAL). Relevant meeting abstracts and reference lists were manually searched. Data analysis was performed using Review Manager Version 5.0 software.

RESULTS

Thirty randomized controlled trials were identified for review. The clinical heterogeneity of IPLA use was high. However, there appeared to be reduced pain, opioid use, and need for rescue analgesia, and reduced postoperative cortisol and glucose responses.

CONCLUSION

There is evidence in favor of IPLA in LC. Further trials of this modality in LC are not needed as these are unlikely to reduce clinical heterogeneity. IPLA should be trialled as future minimally invasive surgical techniques approach.

New concepts in antimalarial use and mode of action in dermatology

Although chloroquine, hydroxychloroquine and quinacrine were originally developed for the treatment of malaria, these medications have been used to treat skin disease for over 50 years. Recent clinical data have confirmed the usefulness of these medications for the treatment of lupus erythematosus. Current research has further enhanced our understanding of the pharmacologic mechanisms of action of these drugs involving inhibition of endosomal toll-like receptor (TLR) signaling limiting B cell and dendritic cell activation. With this understanding, the use of these medications in dermatology is broadening. This article highlights the different antimalarials used within dermatology through their pharmacologic properties and mechanism of action, as well as indicating their clinical uses. In addition, contraindications, adverse effects, and possible drug interactions of antimalarials are reviewed.

Antidepressants, prostaglandins and the prevention and treatment of cancer

Among the putative mechanisms of carcinogenesis are up-regulation of cyclooxygenase, the synthesis and expression of oncogenes, viral activation, signal disruption, failed apoptosis, tumor initiation and promotion, angiogenesis, metastasis, immunosuppression, telomerase activity and autoimmunity. All are regulated by prostaglandins. Observable and radiographic regression of cancer has been documented in patients taking non-steroidal, anti-prostaglandin drugs such as indomethacin and ibuprofen. Antidepressants, too, have prostaglandin-inhibiting properties, and in vivo and in vitro evidence of their antineoplastic actions is emerging.

Necrobiosis lipoidica diabeticorum treated with chloroquine

Necrobiosis lipoidica diabeticorum (NLD) is an idiopathic granulomatous skin disorder. We review previously described therapies from the recent literature and report the first case of successful treatment of NLD with oral chloroquine.

Salicylate and quinine affect the central nervous system

Spontaneous local field potential (LFP) spindle frequencies in cat primary auditory cortex (AI) were estimated from the LFP-trigger autocorrelogram before and after application of sodium salicylate and quinine sulfate. A significant decrease (from 8.7 Hz to 7.6 Hz) was observed. The best modulation frequencies for 251 single units recorded in AI response to periodic click train stimulation also decreased (from 10 Hz to 8.6 Hz) after application of these tinnitus-inducing drugs. The results strongly suggest a central effect of salicylates and quinine in addition to their peripheral ototoxic effects.

Antimalarials in rheumatic diseases

The antimalarials hydroxychloroquine and chloroquine remain established and effective agents for the treatment of rheumatoid arthritis and systemic lupus erythematosus. Although the mechanisms of action remain uncertain, evidence is accumulating that the antirheumatic and immunological effects of the antimalarials are related to their massive distribution into the cellular acid-vesicle system. These drugs are attracting new interest because their relative safety recommends their use in early rheumatoid arthritis and as a component of second-line antirheumatic drug combinations. The absence of data examining the effect of antimalarials upon radiological progression of rheumatoid arthritis needs to be rectified. Recent understanding of the pharmacokinetics of these drugs reveals that steady-state concentrations are not achieved for at least 3-4 months. Preliminary information also suggests a relationship between blood concentrations and effect. Taken together, these data suggest that more effective dosage regimens will be possible when therapeutic concentration ranges are properly established.

Unification of the findings in schizophrenia by reference to the effects of gestational zinc deficiency

The hypothesis presented here suggests that schizophrenia is caused by the action of gestational zinc deficiency on genetically susceptible foetuses. The psychosis seen is suggested to be due to a combination of dietary or otherwise induced zinc deficiency and lack of zinc releasing capacity in the hippocampus. A non genetic but transmissable immune defect is suggested to be relevant to psychosis and to the nonmendelian pattern of inheritance of the disorder.

Biological activity and anti-prostaglandin effects of prostaglandin analogue, ent-11-epi-15-epi PGE2 methyl ester

The biological activity and anti-prostaglandin property of the prostaglandin analogue, ent-11-epi-15-epi PGE2 methyl ester, were studied on isolated guinea pig ileum. Ent-11-epi-15-epi PGE2 methyl ester contracted guinea pig ileum and produced a concentration-response curve parallel to that of PGE2. However, the former exhibited a lower maximal effect than PGE2. At concentrations greater than 10(-6)M, ent-11-epi-15-epi PGE2 methyl ester selectively antagonized contractile actions of PGE2 and PGE2 alpha without affecting contractions induced by acetylcholine. These observations suggest that the PG analogue acted like a competitive antagonist to PGE2 and PGF2 alpha on guinea pig ileum in vitro.

Action of mefloquine on agonist-induced contractions of the guinea-pig isolated ileum

1. Responses of the guinea-pig isolated ileum to cumulative concentrations of acetylcholine (ACh), histamine (H), and prostaglandin E2 (PGE2) were obtained in the presence or absence of mefloquine or quinine. 2. The effects of increasing the external calcium concentration and the presence of a low concentration (1.8 nmol/l) of PGE2 on the mefloquine- and quinine-induced inhibition of the ACh cumulative dose-response curves were also investigated. 3. Mefloquine (1-10 mumol/l) and quinine (50-100 mumol/l) both caused a dose-dependent non-parallel right shift of the log concentration-response curve of every agonist. Mefloquine is a more potent inhibitor of PGE2-induced responses whereas quinine inhibited all three agonist-induced responses to the same extent. 4. Increasing the external calcium concentration enhanced the inhibitory effects of both drugs on ACh-induced responses. Pre-incubation with 1.8 nmol/l PGE2 had a similar effect. 5. The actions of mefloquine on ACh- and H-induced contractions are non-specific, like other antimalarials, but its greater inhibitory action on PGE2 may involve a more complex effect.

Lithium and immune function

Lithium has potent antiviral and immunostimulating properties which are probably consequences of its actions on prostaglandin synthesis. Although lithium has considerable potential in the prophylaxis of some viral illnesses and other manifestations of defective immune function, it is, paradoxically, capable of activating autoimmune mechanisms in predisposed patients.

Antioxidant action of antimalarials

The effects of antimalarials, chloroquine and quinacrine, on the generation of reactive oxygen species were examined both in polymorphonuclear leucocytes and in the xanthine-xanthine oxidase system. Antimalarials showed inhibitory effects on the production of reactive oxygen species probably by affecting cell functions, such as membrane phospholipid methylation. It is suggested that antimalarial agents can work as antioxidants at the site of inflammation protecting against auto-oxidative tissue damage with resultant anti-inflammatory effects.

Inhibition of the metabolism and motility of human spermatozoa by various alkaloids

The ability of several alkaloids to inhibit the metabolism and motility of human spermatozoa has been investigated. Of the agents tested, chloroquine was the most effective in inhibiting sperm metabolism (production of carbon dioxide and lactic acid) and motility. It was active at a concentration of 3.6 x 10(-5)M. Quinine and Quinacrine were active at concentrations of 5 x 10(-4)M and emetine required concentrations as high as 3.6 x 10(-3)M to achieve an inhibitory effect. Detailed studies with emetine showed that the time needed for inhibition of sperm motility was inversely proportional to the drug concentration and directly related to the sperm density. In addition, the inhibition was shown not to be reversible.

Antimalarials

The antimalarials, chloroquine, hydroxychloroquine, and quinacrine, are used primarily for malaria; but they can be beneficial for cutaneous lupus erythematosus (LE), polymorphous light eruption, solar urticaria, and porphyria cutanea tarda. Antimalarials bind to deoxyribonucleic acid (DNA) which prevents DNA and ribonucleic acid (RNA) polymerase reactions and DNA heat inactivation; and they inhibit the LE cell phenomenon, antinuclear antibody reactions, and suppress lymphocyte transformation. By competing with calcium ion, they stabilize membranes and have an anesthetic effect. Their anti-inflammatory potential is due to their inhibition of hydrolytic enzymes, stabilization of lysosomes, interference with prostaglandin synthesis, blocking of chemotaxis, and antagonism of histamine responses. The antimalarials have no sunscreening properties. The most common toxic effects are cutaneous pigmentation, nausea, vomiting, diarrhea, mild ileus, and cycloplegia. There has been a reluctance to use chloroquine and hydroxychloroquine because of the possibility of retinopathy. However, if the "safe" daily dose limit of chloroquine, 2 mg per pound of body weight, and of hydroxychloroquine, 3.5 mg per pound of body weight, is followed, the chance of retinopathy is slight. Quinacrine does not cause retinopathy, but it has more cutaneous side effects than the other two agents.

The reversibility of cancer: the relevance of cyclic AMP, calcium, essential fatty acids and prostaglandin E1

Transformed cells in culture can be normalised (made to undergo reverse transformation) by exposure to cyclic AMP, prostaglandin (PG) E1 and certain drugs. One of these drugs, thioproline, has been successfully used in treating human cancer. All cancer cells have a number of common characteristics: they exhibit aerobic glycolysis, they fail to show feedback regulation of cholesterol biosynthesis, they do not regulate cytoplasmic calcium levels normally and they produce excessive amounts of 2 series PGs. It has been known since 1975 that transformed cells cannot make PGE1 because of loss of the delta-6-desaturase enzyme which converts linoleic acid to gamma-linolenic acid. There is evidence that PGE1 acting in concert with thromboxane A2 has effects which make it able to reverse all the metabolic abnormalities common to all cancer cells. It is therefore argued that loss of the ability to make PGE1 and/or thromboxane A2 may be the critical step in malignant change in many forms of cancer. Restoration of normal PGE1 synthesis by providing gamma-linolenic or dihomogammal inolenic acids which will by-pass the blocked desaturase, whould be of value in normalising malignant cells and reversing cancer growth. Since this approach is completely non-toxic it is here seriously suggested that it might be used as a first step in treatment of those cancers where current evidence suggests that delay in the administration of orthodox treatment is unlikely to affect prognosis.

The mechanism of coronary artery spasm: roles of oxygen, prostaglandins, sex hormones and smoking

A reduced oxygen supply to the heart causes coronary vasodilatation in the first instance. But if the hypoxia is severe or prolonged, the dilatation passes off and coronary vasospasm develops leading to a vicious circle with a further reduction of myocardial oxygenation. The spasm is associated with increased outflow of prostaglandin (PG)-like material and can be prevented or reversed by inhibitors of PG synthesis such as indomethacin or antagonists of PG action such as chloroquine. The spasm does not appear to be caused by thromboxane (TX) A2 since selective inhibitors of TXA2 synthesis enhance the hypoxic spasm and by themselves can cause spasm even in oxygenated hearts. The mechanism may be related to loss of negative feedback control of the PG pathway by TXA2. Oxygen may enhance TXA2 production and reduce formation of vasoconstrictor PGs, while smoking, because of the formation of carboxyhaemoglobin, may have the opposite effect. Oestradiol and testosterone do not influence the hypoxic spasm but progesterone at physiological concentrations blocks it completely. Progesterone may be the protective female hormone and the increased susceptibility to myocardial infarction in women on oral contraceptives may be related to reduced formation of endogenous progesterone.

Prostaglandins and drug induced agranulocytosis, aplastic anaemia and leukemia

Drug like aspirin, indomethacin, phenylbutazone, chloroquine and quinine have been reported to induce agranulocytosis, aplastic anaemia and leukemia. These drugs are also known to interfere with the prostaglandin system at one point or another. Since prostaglandins are known to be involved in the maturation and differentiation of macrophage-granulocyte progenitor cells, in erythropoietin mediated erythropoiesis and in the functional capabilities of leukocytes, it is proposed here that these haematological abnormalities by these drugs could be due to their affect on the prostaglandin system.

Operation or indomethacin for the premature ductus

Indomethacin constricts the patent ductus arteriosus in approximately 70% of premature infants, but temporarily inhibits synthesis of all prostaglandins. Early toxicity of indomethacin is not prohibitive, but the possibility of late neurological deficits is raised by results of laboratory experiments. As yet, no late toxic effects of indomethacin have been observed. However, this possibility and the low morbidity (less than 2%) and mortality (less than 2%) of surgical ligation of the patent ductus arteriosus in premature infants favor operation except in carefully controlled and limited clinical trials.

Role of prostaglandins in human fertility

One function of prostaglandins in semen may be suppression of an anti-sperm immune response.

A defect in thromboxane A2 synthesis may be a factor predisposing to cancer

A failure of thromboxane (TX) A2 synthesis may be a factor in cancer. Such a loss could explain the susceptibility to mutation, the excess prostaglandin production, the glycolytic mode of metabolism and the deranged calcium pumping characteristic of cancers. Ionising radiation and phorbols both have actions similar to inhibitors of TXA2 synthesis whereas colchicine and oxygen have actions consistent with stimulation of TXA2 synthesis. The concept accounts logically for hitherto unexplained features of cancer and suggests new strategies for the prevention and treatment of cancer.

Complete heart block due to chronic chloroquine toxicity managed with permanent pacemaker

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Prostaglandins and schizophrenia: further discussion of the evidence

It has been proposed that schizophrenia is a prostaglandin-deficiency disease and also that it is a disease of prostaglandin excess. New evidence is reviewed which suggests that 'classic' schizophrenia is due to a specific deficiency of prostaglandin E1 while certain toxic and vitamin-deficiency psychoses may be due to a broader spectrum of prostaglandin deficiency. There is also good evidence that a particular schizophrenic subgroup, which includes catatonic schizophrenia but may not be confirmed to it, is associated with an excess of prostaglandins. Part of the explanation may be that prostaglandin E1 has a 'bell-shaped' dose-response curve with high concentrations having effects similar to those of prostaglandin deficiency.

Inhibition of the algesic effect of bradykinin and acetylcholine by mepacrine

1. The isolated perfused rabbit ear connected to the body by its nerve only was used to investigate the influence of mepacrine on the algesic effect of bradykinin and acetylcholine. For comparison, quinidine was included in this investigation. 2. Infusion of mepacrine or quindine (2-10 microgram/ml) into the rabbit ear reduces the algesic effect of bradykinin as well as of acetylcholine in proportion to the dose. 3. Infusion of postglandin E1 (10 ng/ml) in addition to mepacrine or quinidine restores theinhibited algesic effect of bradykinin more than that of acetylcholine. 4. Mepacrine and quinidine (10 microgram/ml) reduce the brief vasoconstriction elicited by bradykinin in the rabbit ear. 5. The results suggest that mepacrine or quinidine reduce the algesic effect of bradykinin primarily by inhibiting the release of E-type prostaglandins which sensitize pain receptors and secondarily by an unspecific antagonism (local-anaesthetic action). The effect of acetylcholine, however, appears to be reduced mainly by an unspecific antagonism.

Myo-inositol in physiological concentrations stimulates production of prostaglandin-like material

In physiological concentrations myo-inositol stimulated production of prostaglandin (PG)-like material in a rat mesenteric vascular bed preparation. There were five lines of evidence: 1. Inositol potentiated pressor responses to both norepinephrine and potassium in a manner similar to PGE2. 2. Inositol had no potentiating effect in preparations in which endogenous PG production was blocked by indomethacin. 3. Inositol caused no further potentiation in preparations already potentiated by arachidonic acid, the PG precursor. 4. The inhibitory effect of the PG antagonist chloroquine was reduced in an apparently competitive manner by inositol. 5. As indicated by rat stomach bioassay inositol caused a three fold rise in the outflow of PG-like material from the preparation.

The relationships between cyclic AMP, calcium and prostaglandins as second messengers

There is considerable dissatisfaction with present second messenger hypotheses involving cyclic nucleotides and calcium. The recent findings that methyl xanthines and adenosine are prostaglandin antagonists casts doubt on much of the evidence in favour of the cyclic AMP hypothesis. There is evidence that allosteric sites may modify the binding of calcium and cyclic nucleotides to key cellular regulators and that a range of substances including steroids, adenosine and prostaglandins may occupy those sites. This concept introduces much needed flexibility into the second messenger concept, allows many experiments to be reinterpreted and has major implications throughout the biomedical sciences.