Drugs, alcohol and driving.

Driving a car is a complex psychomotor and perceptual task which is subject to impairment by many factors. Several workers have studied the potential effects of drugs and alchol in crash production by epidemiological and laboratory studies. Both types of studies have yielded useful data but their limitations must be borne in mind when applying the results in pratice. Alcohol is obviously the most common single cause of traffic accidents. A progessively increased risk with increasing blood alcohol levels is well documented; fatigue and/or drugs increase this risk. Drugs are related much more infrequently to traffic accidents although on the basis of statistics, there is a potential risk with drug use. However, drugs alone are not as important as alcohol. The most significant drugs as regards driving risk are obviously certain antianxiety agents, hypnotics, stimulants, hallucinogens, marihuana, lithium and narcotic analgesics, as well as ganglionic blocking agents, insulin and sulphonylurea derivates. Patients should not drive after taking these drug until they are objectively fully alert and capable. Anticholinergics, antihistamines, antidepressants, antipsychotics, phenybutazone, indomethacin, alpha-methyldopa, and beta-blockers may in some cases cause central side effects (e.g. drowsiness) strong enough to affect driving performance. After starting therapy with these drugs, or after a significant change in dose, driving should be avoided until it is known that unwanted effects do not occur. Psychotropic drugs may enhance the deleterious effect of alcohol, and with most hypnotics there is still an effect the next morning. Some drugs (e.g. anticonvulsants or antiparkinsonian drugs) may make driving safer, but the disease (epilepsy, Parkinsonism, cardiovascular diseases, psychic disorders, etc.) ofter precludes driving. Clinicians should warn their patients about an impairment of driving skills if this is likely to occur due to the drug or the illness concerned.     

Drug-related lupus. Incidence, mechanisms and clinical implications.

Adverse side effects to drugs and chemicals in which immune mechanisms may be responsible have been described in drug-related lupus (DRL). The spectrum of drugs that may elicit DRL includes such classes as the hydrazines, arylamines, and chemicals that can be metabolised to amines. The 2 major pathways of metabolism--acetylation and N-hydroxylation--are described in detail. The events leading to autoantibody production are not well understood; however, specific consideration of the genetic makeup of patients who are candidates for treatment with these drugs may help identify those at risk of developing DRL.     

The second Lilly Prize Lecture, University of Newcastle, July 1977. beta-Adrenergic receptor blockade in hypertension, past, present and future.

All beta-adrenoceptor blocking drugs that have been described share the common property of being competitive inhibitors. They differ in their associated properties, the presence or absence of cardioselectivity, membrane stabilizing activity, and partial agonist activity. Recently some beta-adrenoceptor blocking drugs have been reported which also possess alpha-adrenoceptor blocking activity. The associated properties have been used as a basis for classifying beta-adrenoceptor blocking drugs (Fitzgerald, 1969, 1972). The presence or absence of cardioselectivity is most useful for dividing beta-adrenoceptor blocking drugs. The non-selective drugs (Division I) can be further divided according to the presence or absence of intrinsic sympathomimetic activity (ISA) and membrane stabilizing activity (Fitzgerald's groups I-IV). Group I possess both membrane activity and ISA, e.g. alprenolol, oxprenolol, group II just membrane action, e.g. propanolol, group III ISA but no membrane action, e.g. pindolol. Fitzgerald placed pindolol in group I but should be placed in group III as it possesses a high degree of beta-adrenoceptor blocking potency in relation to its membrane activity (Prichard, 1974). Finally drugs in group IV have neither ISA nor membrane action, e.g. sotalol, timolol. The cardioselective drugs (Division II) can be similarly sub-divided into groups I-IV according to the presence or absence of ISA or membrane action (Fitzgerald grouped all these together as group V). Lastly there are new beta-adrenergic receptor blocking drugs which in addition have alpha- adrenergic receptor blocking properties (Division III).     

Antiarrhythmic drug classifications. A critical appraisal of their history, present status, and clinical relevance.

Classifications of antiarrhythmic drugs have developed because of a need to organize the large number of agents available according to pharmacological properties of clinical relevance. The current classification is a hybrid of classification systems developed in the early 1970s. It subdivides drugs according to 4 major pharmacological actions: (a) depression of phase 0 sodium current; (b) antagonism of adrenergic effects on the heart; (c) prolongation of of action potential duration; and (d) calcium channel blockade. Further subdivision of sodium channel blockers is based on the kinetics of sodium channel blockade and drug effects on action potential duration. A critical analysis of selected aspects of the clinical actions of antiarrhythmic drugs indicates the value of the current classification, as well as some limitations in its ability to separate drugs into distinct groups with characteristic clinical properties. The strengths of the current classification are due to the clinical importance of the pharmacological properties on which it is based. These results in electrophysiological actions, indications, and adverse effects that are typical for each group of drugs. The limitations of the current system relate to the propensity of individual drugs to have actions of more than one class simultaneously, the way that the various actions of a given drug are dependent on concentration, rate, and tissue type, and to problems in subclass definition. Some of these shortcomings could be alleviated by returning to the concept, originally put forward by Singh and Vaughan Williams, of classes of drug action rather than classes of drug per se. This approach would be pharmacologically more realistic than trying to assign each antiarrhythmic agent to a single unique class, would be better able to incorporate the complexities of drug action, and would potentially be more flexible. The wide use of antiarrhythmic drug classifications attests to their value, and suggests that they are likely to continue to be important in the future.     

Urinary screening for alprazolam, triazolam, and their metabolites with the EMIT d.a.u. benzodiazepine metabolite assay

Alprazolam (Xanax) and triazolam (Halcion) are relatively new triazolobenzodiazepines that are anxiolytic and hypnotic. This study assesses the reactivity of these drugs and their major metabolites in the EMIT d.a.u. benzodiazepine metabolite assay. Analytical standards of drugs and metabolites and urine specimens from patients receiving these drugs were analyzed by EMIT. Alprazolam and alpha-OH alprazolam gave an equivalent response to the EMIT low calibrator between 0.2 and 0.3 microgram/mL. Triazolam and alpha-OH triazolam were reactive between 0.3 and 0.5 microgram/mL. The assay was positive in 24 out of 27 random urine specimens from alprazolam-treated patients and in 8 out of 19 urine specimens from triazolam-treated patients. Positive urine results were confirmed by measuring the major urinary metabolites alpha-OH alprazolam and alpha-OH triazolam by HPLC. The study demonstrates that the EMIT assay can detect significant amounts of alprazolam and metabolites in the urine. The assay was negative in 58% of the specimens from individuals receiving triazolam, however.     

Dopamine receptor blockade and the neuroleptics, a crystallographic study.

The X-ray structures of 12 drugs of the tricyclic class having varying pharmacological profiles have been examined in detail in an attempt to rationalize the known structure-activity relations of neuroleptic drugs with respect to their ability to block dopamine receptors in the brain. Further evidence is presented in support of the theory that the neuroleptics are able to block dopamine receptors because of a conformational complementarity between certain portions of these drugs and dopamine.     

P450 enzymes. Inhibition mechanisms, genetic regulation and effects of liver disease.

Multiple hepatic P450 enzymes play an important role in the oxidative biotransformation of a vast number of structurally diverse drugs. As such, these enzymes are a major determinant of the pharmacokinetic behaviour of most therapeutic agents. There are several factors that influence P450 activity, either directly or at the level of enzyme regulation. Drug elimination is decreased and the incidence of drug interactions is increased when there is competition between 2 or more drugs for oxidation by the same P450 enzyme. The available knowledge concerning the relationship between the presence of certain functional groups within the drug structure and inhibition of P450 activity is increasing. In many instances, it is possible to associate inhibition with certain drug classes, e.g. antimycotic imidazoles and macrolide antibiotics. Disease states, especially those with hepatic involvement, and the genetic makeup of the individual are conditions in which some P450s may be downregulated (that is, the enzyme concentrations in liver are decreased), with associated slower rates of drug elimination. In these individuals, dosages of drugs that are substrates for downregulated P450s should be decreased. Exposure to environmental pollutants as well as a large number of lipophilic drugs can result in induction (upregulation) of P450 enzyme activity. This raises the issue of previous approaches to the study of P450 induction in vivo. The use of human hepatocyte preparations in culture is a promising new direction that could assist the determination of modifications to drug therapy necessitated by exposure to inducing agents. Until such information is obtained, however, the use of drugs known to increase the microsomal expression of particular P450s, and increase associated drug oxidation capacity in humans, should be used with caution.     

A review of possible mechanisms of action of the antirheumatic drug, alclofenac.

A number and variety of hypotheses have been proposed to explain the primary mechanism of action of the antirheumatic drugs. A critical review is made of the biochemical and pharmacological parameters which, on current evidence, parallel the clinical activity of the drugs. The numerous chemical mediators of the inflammatory response are discussed, as is the possible role of endoenous anti-inflammatory substances. Particular attention is paid to the plasma protein-binding effects of antirheumatic drugs and the competitive displacement theory of drug action is examined in the light of recent work on the behaviour of L-tryptophan binding in vitro and in vivo. It is suggested that antirheumatic drugs can be differentiated by their influence on the acute-phase protein response and their effects on tryptophan binding. Clinical findings are reviewed to support the proposal that drugs such as alcofenac, which both inhibit the acute-phase response and exert prolonged influence on the binding of tryptophan to plasma proteins, reduce inflammatory activity more profoundly than those drugs which produce symptomatic relief alone. They are capable, therefore, of altering the course of the disease.     

Evaluation of methods to determine protein-binding of drugs. Equilibrium dialysis, ultrafiltration, ultracentrifugation, gel filtration

The reliability of the most important methods to determine protein-binding of drugs was compared. Applying these methods to different drugs solved in bovine plasma or in protein-free solutions the incidence of errors specific for each method was examined. Certain limits are found for the applicability of each method. If these limitations are observed reproducibility differs only slightly within the four methods. Considering all the results, however, the values achieved by equilibrium dialysis appear to come closest to the real extent of binding.     

Poisoning in the elderly. Epidemiological, clinical and management considerations.

Poisoning is a significant problem in the elderly. The majority of poisonings in older people are unintentional and may result from dementia and confusion, improper use of the product, improper storage or mistaken identities. Depression is also common in the elderly and suicide attempts are more likely to be successful in this age group. The elderly patient's recuperative abilities may be inadequate as a result of numerous factors including impaired hepatic or renal function as well as chronic disease processes. General management of poisoning in the elderly parallels management of younger adults, but it is especially important to ascertain underlying medical conditions and concurrent medications. In most poisonings, activated charcoal and cathartic are sufficient. Haemodialysis or haemoperfusion may be required at lower plasma drug concentrations in elderly patients. While the specific indications for antidotes are the same for all age groups, dosage alterations and precautions may need to be considered in the elderly. Drugs most often implicated in poisonings in the elderly include psychotherapeutic drugs, cardiovascular drugs, analgesics and anti-inflammatory drugs, oral hypoglycaemics and theophylline. Cardiovascular and neurological toxicities occur with overdoses of neuroleptic drugs and, more frequently and severely, with cyclic antidepressants. Patients with pre-existing cardiovascular disease are at particular risk of worsening ischaemic heart disease and congestive heart failure. Benzodiazepines only appear to produce significant toxicity during long term administration or in combination with other CNS depressants. Digoxin can cause both chronic and acute intoxication, most seriously cardiac toxicity including severe ventricular arrhythmias, second or third degree heart block or severe refractory hyperkalaemia. Immune Fab antibody is indicated for the management of digoxin toxicity, although patients dependent on the inotropic effect of digoxin may develop heart failure after digoxin Fab antibody administration. Nitrates can cause toxicity including headache, vomiting, hypotension and tachycardia from excessive sublingual, transdermal or intravenous doses. Conduction disturbances and hypotension occur with overdoses of antihypertensive drugs; these effects are mild with angiotensin converting enzyme (ACE) inhibitors, occasionally severe with beta-blockers and of significant concern with calcium channel antagonists. The elderly commonly use aspirin and other salicylates, are more likely to develop chronic intoxications to these agents, and are more susceptible to severe complications such as pulmonary oedema. Salicylate poisoning, recognition of which is often delayed, should be considered in elderly patients with neurological abnormalities or breathing difficulties, especially in the setting of acid-base abnormalities. The clinical effects of NSAID overdose are mild and usually involve the central nervous system and gastrointestinal tract.(ABSTRACT TRUNCATED AT 400 WORDS)     

HPMA copolymer-anticancer drug conjugates: design, activity, and mechanism of action.

The design, synthesis and properties of N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers as carriers of anticancer drugs are reviewed. Macromolecular therapeutics based on HPMA copolymers are biocompatible, preferentially accumulate in tumors, and possess a higher anticancer efficacy than low molecular weight drugs. Novel designs of HPMA copolymer carriers resulted in long-circulating conjugates and gene and oligonucleotide delivery systems. HPMA copolymer based macromolecular therapeutics were active against numerous cancer models and are in clinical trials. The data obtained indicated that macromolecular therapeutics activated different signaling pathways and possessed a different mechanism of action than free drugs. This bodes well for the success of future research aimed at identification of new intracellular molecular targets as a basis for the design of the second generation of macromolecular therapeutics.     

Drug-induced respiratory disorders: incidence, prevention and management.

Various drugs are associated with adverse respiratory disorders (ARDs) ranging in severity from mild, moderate to severe and even fatal. Cardioselective and nonselective beta-blockers, calcium antagonists and dipyridamole can induce asthma. ACE inhibitors are mainly associated with cough. Amiodarone is related to a form of interstitial pneumonitis (IP) which can be fatal, tocainidine and flecainidine to a form of IP, and hydrochlorothiazide to a form of IP and pulmonary oedema. Antiasthmatic drugs can be associated with a paradoxical bronchospasm, while leukotriene antagonists are linked to the development of Churg-Strauss syndrome. Nonsteroidal anti-inflammatory drugs including aspirin (acetylsalicylic acid) may induce asthma. Gold is mainly related to IP, penicillamine to IP, systemic lupus erythematosus, bronchiolitis obliterans, and Goodpasture's syndrome. Acute respiratory reactions to nitrofurantoin include dyspnoea, cough, IP, and pleural effusion while IP and fibrosis are common in chronic reactions. Other antibacterials mainly evoke pneumonitis, pulmonary infiltrates and eosinophilia, and bronchiolitis obliterans. ARDs are similar for most categories of cytotoxic agents, with chronic pneumonitis and fibrosis being the most common. Noncardiogenic pulmonary oedema occurs as the most common respiratory complication in opioid agonist addiction. Psychotropic drugs such as phenothiazides, butyrophenones and tricyclic antidepressants can also induce pulmonary oedema. Oral contraceptives may produce asthma exacerbation, while long term use and/or high doses of postmenopausal hormone replacement therapy increase the risk of asthma. Bromocriptine is mainly associated with pleural effusion, while methysergide is usually associated with pleural effusion and fibrosis. Some anorectic agents have been linked to the development of primary pulmonary hypertension. The possibility of the occurrence of ARDs should be taken into account in each individual patient. Although in most cases the adverse effects are unpredictable, they can be reduced to a minimum or prevented if some drugs are avoided or stopped in time.     

Drug-induced nephrotoxicity. Aetiology, clinical features and management

There is a growing number of hospitalised patients who develop a drug-induced renal problem because increasing numbers of potent drugs have been added to the therapeutic arsenal in recent years. The 3 clinical syndromes that can be recognised in drug-induced nephropathy are acute renal failure, chronic interstitial nephritis and the nephrotic syndrome. The first can be caused by prerenal problems, acute interstitial nephritis, acute tubular necrosis and intratubular obstruction. The most important drugs that cause prerenal failure are NSAIDs, captopril and cyclosporin. NSAIDs inhibit the synthesis of prostaglandins, and consequently vasoconstriction of the afferent arteriole leads to lowering of the glomerular filtration rate (GFR); captopril blocks the formation of angiotensin II (which also leads to a lower GFR), and should be used with caution in patients with stenotic renal arteries; cyclosporin causes vasoconstriction of the afferent arteriole, which is probably mediated by the sympathetic system. Combinations of these drugs result in increased nephrotoxicity. The drugs most likely to cause acute interstitial nephritis are antibiotics and NSAIDs. Normally, signs of an allergic reaction are also present. Acute interstitial nephritis is usually self-limiting, but in some studies it is claimed that steroids may promote recovery. Four important causal agents of acute tubular necrosis are aminoglycosides, amphotericin B, radiocontrast agents and cyclosporin. Approximately half of the cases of drug-induced renal failure are related to the use of aminoglycosides: generally, 10 days after start of treatment a nonoliguric renal failure develops, with recovery after withdrawal of the drug in almost all cases. The aminoglycosides are particularly nephrotoxic when combined with other nephrotoxic drugs. 80% of amphotericin B-treated patients develop renal insufficiency, a percentage that increases as the cumulative dose exceeds 5g. It is because of its unique antifungal properties that there are still some indications for the use of this highly nephrotoxic drug; the high percentage of nephrotoxicity can probably be prevented in part by sodium loading. The nephrotoxicity of radiocontrast agents is largely dependent on renal function: from 0.6% in patients with normal renal function to 100% in patients with a serum creatinine above 400 mumol/L. Diabetes mellitus does not add greatly to the risk of radiocontrast nephrotoxicity. The nephrotoxicity of cyclosporin is dose-dependent and reversible, although there are some reports of irreversibility after long term use. Cyclosporin can also result in nephrotoxicity in combination therapy.(ABSTRACT TRUNCATED AT 400 WORDS)     

Quinoline-containing antimalarials--mode of action, drug resistance and its reversal. An update with unresolved puzzles.

Malaria constitutes one of the major health threats in the tropical and sub-tropical areas of the world. Yet, few advances were made in recent years in revealing the mode of action of the common and most economically affordable antimalarial drugs, the schizontocidal 4-aminoquinolines. Data presented indubitably repudiate the previous notions that these drugs act by either halting the feeding of the parasite on its host erythrocyte cytosol or repressing nucleic acid synthesis due to intercalation into the parasite's DNA. A novel target for drugs is outlined, i.e. they are shown to inhibit in vitro the release of iron from acidified host cell cytosol, consisting mostly of hemoglobin, a process that could provide this trace element to the parasite. Resistance to quinoline-containing drugs is the principal reason for the present resurgence of malaria. Drug-resistant parasites accumulate less of these weak base-like drugs in the acidic digestive vacuoles. A kinetic model is presented, indicating that diminishing drug accumulation is due to decreased vacuolar proton pump activity and is not a result of a putative multidrug resistance (MDR) efflux pump. Findings to date on the molecular biology of parasite mdr genes are reviewed. These indicate no correlation between gene expression or mutations and phenotypic drug resistance. Reversal of parasite drug resistance by relevant compounds in MDR cancer cells seems to involve mechanism(s) different from the inhibition of the MDR pump in cancer cells.     

Drug-induced oesophageal disorders: pathogenesis, incidence, prevention and management.

Drug-induced injury of the oesophagus is a common cause of oesophageal complaints. 'Pill-induced' oesophagitis is associated with the ingestion of certain drugs and accounts for many cases of erosive oesophagitis. To date, more than 70 drugs have been reported to induce oesophageal disorders. Antibacterials such as doxycycline, tetracycline and clindamycin are the offending agents in more than 50% of cases. Other commonly prescribed drugs that cause oesophageal injury include aspirin (acetylsalicylic acid), potassium chloride, ferrous sulfate, quinidine, alprenolol and various steroidal and nonsteroidal anti-inflammatory agents. However, many physicians and even more patients are not aware of this problem. Capsules or tablets are commonly delayed in their passage through the oesophagus. Highly caustic coatings, direct medication injury and poor oesophageal clearance of pills can lead to acute inflammation. Oesophageal damage occurs when the caustic contents of a drug remain in the oesophagus long enough to produce mucosal lesions. Taking medications at bedtime or without fluids is a common cause of oesophagitis. The possibility of drug-related damage should be suspected in all cases of oesophagitis, chest pain and dysphagia. History and gastrointestinal endoscopy will confirm the diagnosis. Treatment is supportive, although acid reduction is used frequently as an adjunct. This review reflects the current state of knowledge in this field.     

Design, monitoring, and analysis issues relative to adverse events.

In the clinical development of new drugs for market approval, it is frequently impossible to design trials to provide definitive information about safety--particularly about adverse events. It is possible, however, to design most trials to provide definitive information about efficacy. Efficacy trials with new drugs should therefore be monitored for safety, and the safety profile described within and across trials. Confidence intervals are recommended as the appropriate statistical methodology for doing this. Such intervals provide an interval estimate on the unknown incidences of adverse experiences among patients who could be treated with each regimen, as well as permit a conclusion that two regimens are different.     

Drug-induced cutaneous photosensitivity: incidence, mechanism, prevention and management.

The interaction of sunlight with drug medication leads to photosensitivity responses in susceptible patients, and has the potential to increase the incidence of skin cancer. Adverse photosensitivity responses to drugs occur predominantly as a phototoxic reaction which is more immediate than photoallergy, and can be reversed by withdrawal or substitution of the drug. The bias and inaccuracy of the reporting procedure for these adverse reactions is a consequence of the difficulty in distinguishing between sunburn and a mild drug photosensitivity reaction, together with the patient being able to control the incidence by taking protective action. The drug classes that currently are eliciting a high level of adverse photosensitivity are the diuretic, antibacterial and nonsteroidal anti-inflammatory drugs (NSAIDs). Photosensitising chemicals usually have a low molecular weight (200 to 500 Daltons) and are planar, tricyclic, or polycyclic configurations, often with heteroatoms in their structures enabling resonance stabilisation. All absorb ultraviolet (UV) and/or visible radiation, a characteristic that is essential for the chemical to be regarded as a photosensitiser. The photochemical and photobiological mechanisms underlying the adverse reactions caused by the more photoactive drugs are mainly free radical in nature, but reactive oxygen species are also involved. Drugs that contain chlorine substituents in their chemical structure, such as hydrochlorthiazide, furosemide and chlorpromazine, exhibit photochemical activity that is traced to the UV-induced dissociation of the chlorine substituent leading to free radical reactions with lipids, proteins and DNA. The photochemical mechanisms for the NSAIDs that contain the 2-aryl propionic acid group involve decarboxylation as the primary step, with subsequent free radical activity. In aerated systems, the reactive excited singlet form of oxygen is produced with high efficiency. This form of oxygen is highly reactive towards lipids and proteins. NSAIDs without the 2-arylpropionic acid group are also photoactive, but with differing mechanisms leading to a less severe biological outcome. In the antibacterial drug class, the tetracyclines, fluoroquinolones and sulfonamides are the most photoactive. Photocontact dermatitis due to topically applied agents interacting with sunlight has been reported for some sunscreen and cosmetic ingredients, as well as local anaesthetic and anti-acne agents. Prevention of photosensitivity involves adequate protection from the sun with clothing and sunscreens. In concert with the preponderance of free radical mechanisms involving the photosensitising drugs, some recent studies suggest that diet supplementation with antioxidants may be beneficial in increasing the minimum erythemal UV radiation dose.     

Acebutolol, atenolol, and propranolol and metabolic responses to acute hypoglycaemia in diabetics.

In a double-blind crossover study the symptomatic and metabolic effects of propranolol, acebutolol, and atenolol were studied during insulin-induced hypoglycaemia in diabetics treated with diet or hypoglycaemic tablets. All the drugs prevented tachycardia, but did not affect the other symptoms of hypoglycaemia. Propranolol delayed the recovery of the blood glucose concentration and impaired the secondary rise in the concentrations of blood lactate and non-esterified fatty acids in diet-treated diabetics. Acebutolol potentiated the hypoglycaemic effect of insulin in tablet-treated diabetics (mean difference of blood glucose concentration 0.7 mmol/l (12.6 mg/100 ml)) and this difference was maintained during the recovery phase4 the blood lactate response was also impaired. Atenolol did not differ perceptibly from placebo in its effect on the metabolic responses to acute hypoglycaemia. The results may be explained by differences in the known pharmacological actions of these drugs. They support the hypothesis that beta-adrenoreceptor blocking drugs that are highly beta1 specific and without membrane-stabilising activity should be safer than the non-selective drugs when used in diabetic patients at risk from hypoglycaemia.     

Dopamine receptor sequences. Therapeutic levels of neuroleptics occupy D2 receptors, clozapine occupies D4.

Dopamine (DA) D2, D3, and D4 receptors are targets for antipsychotic drugs. The recent cloning, deoxyribonucleic acid sequencing, and brain location of these receptors provide new insight on the DA hypothesis of schizophrenia, particularly for the basis of antipsychotic therapy of schizophrenia. In schizophrenia brain tissue, D2 receptors are elevated and have lost the link to D1 receptors. Brain positron-emission tomography studies of patients may also reveal elevated D2, depending on the method used. Hallucinations and positive symptoms are blocked when about 70% of the D2 receptors are occupied by neuroleptic drugs. An analysis of the literature indicates that therapeutic concentrations of antipsychotic drugs (in the patient's cerebrospinal fluid or plasma water) act primarily at D2 receptors, with the exception of clozapine, which acts at D4 receptors.