The cyclodextrin sugammadex and anaphylaxis to rocuronium: is rocuronium still potentially allergenic in the inclusion complex form?

Rocuronium, a non-depolarizing neuromuscular blocking drug has a rapid onset of action, a comparatively low potency and, with a more favourable side effects profile than succinylcholine, it has become a popular alternative to that drug for rapid sequence inductions in anaesthesia. The rocuronium-binding cyclodextrin derivative sugammadex, prepared by per-6 substitution of the primary hydroxyls of γ-cyclodextrin with thiol ether-linked propionic acid side chains to extend the hydrophobic cavity to accommodate rocuronium, is used to reverse neuromuscular blockade by encapsulating the drug as an inclusion complex and removing it from the neuromuscular junction to the plasma. It has recently been suggested that sugammadex might also be of value in the management of rocuronium-induced anaphylaxis and this has been potentially supported by recent case reports. However, before sugammadex can be recommended for this purpose, it is important to establish whether or not the allergenic substituted ammonium groups at each end of the rocuronium molecule in the inclusion complex are masked within the cavity or left exposed for interaction with rocuronium-reactive IgE antibodies in the sera of rocuronium-allergic patients. Detailed experimental strategies and experimental protocols to investigate the allergenic potential of the sugammadex-rocuronium inclusion complex are presented and a possible explanation of the apparently rapid and successful reversal of anaphylaxis by administration of sugammadex is advanced and discussed.

Histamine-releasing and allergenic properties of opioid analgesic drugs: resolving the two.

Opioid analgesics are amongst the most commonly administered drugs in hospitals. Whether natural or synthetic, they show some common structural features, morphine-like pharmacological action and binding specificity for complementary opioid receptors. Tramadol differs from the other opioid analgesics in possessing monoaminergic activity in addition to its affinity for the µ opioid receptor. Many opioids are potent histamine releasers producing a variety of haemodynamic changes and anaphylactoid reactions, but the relationship of the appearance of these effects to the histamine plasma concentration is complex and there is no direct and invariable relationship between the two. Studies of the histamine-releasing effects, chiefly centred on morphine, reveal variable findings and conclusions often due to a range of factors including differences in technical measurements, dose, mode of administration, site of injection, the anatomical distribution of histamine receptors and heterogeneity of patient responses. Morphine itself has multiple direct effects on the vasculature and other haemodynamically-active mediators released along with histamine contribute to the variable responses to opioid drug administration. Despite their heavy use and occasional apparent anaphylactic-like side-effects, immunoglobulin E antibody-mediated immediate hypersensitivity reactions to the drugs are not often encountered. Uncertainties associated with skin testing with these known histamine-releasers, and the general unavailability of opioid drug-specific immunoglobulin E antibody tests contribute to the frequent failure to adequately investigate and establish underlying mechanisms of reactions by distinguishing anaphylactoid from true anaphylactic reactions. Clinical implications for diagnosis of reactions and some speculations on the rarity of true Type 1 allergies to these drugs are presented.

Drug-specific cyclodextrins with emphasis on sugammadex, the neuromuscular blocker rocuronium and perioperative anaphylaxis: implications for drug allergy.

Cyclodextrins, oligosaccharides linked in a circular arrangement around a central cavity, are used extensively in the pharmaceutical industry to improve drug delivery. Their usefulness depends on their capacity to form a drug inclusion, or host-guest, complex within the cavity. In an attempt to improve the delivery of the widely used neuromuscular blocking drug (NMBD) rocuronium, a rocuronium inclusion complex was formed with a chemically modified γ-cyclodextrin. The high binding affinity and specificity of the modified carrier (named sugammadex) for rocuronium (and other aminosteroid NMBDs) led to its use in anaesthesia as an innovative and useful agent for rapid reversal of rocuronium-induced neuromuscular block by sequestering the drug as an inclusion complex. This, in turn, led to the suggestion that sugammadex might be useful to remove the NMBD from the circulation of patients experiencing rocuronium-induced anaphylaxis, a suggestion subsequently supported in case reports where traditional treatment had failed. Successful resuscitations suggested that sugammadex might be a valuable new treatment for such intractable cases but, given the inappropriateness of clinical trials, confirmation or refutation will have to await the slow accumulation of results of individual case reports. Important questions related to antibody accessibility of drug allergenic structures on the rocuronium-sugammadex inclusion complex, and the competition between sugammadex and IgE antibodies (both free and cell bound) for rocuronium, also remain and can be investigated in vitro. The sugammadex findings indicate that the use of carrier molecules such as the cyclodextrins to improve drug delivery will sometimes give rise to changed immunologic and allergenic behaviour of some drugs and this will have to be taken into account in preclinical drug safety assessments of drug-carrier complexes. The possibility of encapsulating and removing other allergenic drugs, e.g., penicillins and cephalosporins, in cases of difficult-to-reverse anaphylaxis to these drugs is discussed.

On the origin and specificity of antibodies to neuromuscular blocking (muscle relaxant) drugs: an immunochemical perspective.

Following the demonstration 25 years ago that substituted ammonium groups on neuromuscular blocking drugs (NMBDs) are the main allergenic structures recognized by IgE antibodies in the sera of some patients who experience anaphylaxis during anaesthesia, immunoassays for these drugs were quickly applied to supplement skin tests in the diagnostic assessment of suspected adverse reactions to anaesthetic agents. Many subjects who react to an NMBD do so on first exposure and this led to the speculation that the origin of allergic sensitization is an environmental agent(s) or another drug containing an ammonium ion. Direct antibody binding and hapten inhibition studies revealed that morphine, which contains a tertiary amino group, was strongly recognized by IgE in sera from anaphylactic patients and a morphine-solid phase immunoassay was found to be superior to NMBD-based assays for the detection of NMBD-reactive IgE antibodies. Extensive inhibition experiments indicate the likelihood of antibody combining site heterogeneity with recognition at the fine structural level of features additional, and adjacent to, ammonium ions. Further quantitative investigations are needed to identify these neighbouring groups on different NMBDs. Recent work has implicated the morphine analogue pholcodine as the sensitizing agent in Norway where, unlike Sweden, anaphylactic reactions to NMBDs are not uncommon and the medicament is available over-the-counter. This has led to the suggestion that allergenic sensitization to the ammonium group of pholcodine may account for the different incidences of anaphylaxis during anaesthesia in the two countries. This work is subjected to critical review and some alternative speculations on the nature and origin of the sensitizing agent(s) are presented.

beta-Lactam allergenic determinants: fine structural recognition of a cross-reacting determinant on benzylpenicillin and cephalothin.

BACKGROUND: An appreciation of the structural heterogeneity of allergenic determinants on penicillins and cephalosporins reveals the importance of side-chain groups and their involvement in many allergies to beta-lactam drugs. Although allergenic cross-reactions between penicillins and cephalosporins are known to occur, the precise molecular bases of such recognitions and cross-sensitivities have rarely been studied and identified. OBJECTIVES: The unexpected finding of a high incidence of positive IgE antibody reactions with both benzylpenicillin and cephalothin prompted serological and immunochemical studies to identify the chemical basis of antibody recognition of these drugs from the two different families of beta-lactam antibiotics. METHODS: Adsorption studies were employed to identify whether or not a single population of antibodies was involved in the recognition of benzylpenicillin and cephalothin. Identification of the fine structural features recognized by IgE antibodies was investigated by quantitative hapten inhibition studies employing carefully selected beta-lactam drugs, analogues and some other structurally related chemicals. RESULTS: Adsorption studies with penicilloic acid-solid phase clearly established that a single population of cross-reacting antibodies recognized both benzylpenicillin and cephalothin. Quantitative inhibition findings, especially with phenylacetic acid and 2-thiopheneacetic acid and with cephaloridine and cefoxitin, which have the same (2-thienyl)methyl side-chain as cephalothin, implicated the methylene group as the focus of the allergenic determinant recognized on benzylpenicillin and cephalothin. In addition to the methylene group, recognition graded into neighbouring structures including the amide group and extended weakly to the beta-lactam ring. CONCLUSIONS: Results confirmed that structural features as small as a methylene group may be allergenically important. In the present case, this group, making up only part of the different side-chains on benzylpenicillin and cephalothin, together with neighbouring structures extending toward the beta-lactam ring, accounted for the cross-reactivity seen between structures that, at first sight, appear to be not closely related. Such subtle, small, common structural features are likely to be immunologically recognized and implicated in allergic reactions to other drugs, including beta-lactam antibiotics.

Fine structural recognition specificities of IgE antibodies distinguishing amoxicilloyl and amoxicillanyl determinants in allergic subjects.

IgE antibodies in the sera of subjects allergic to beta-lactam antibiotics detect a spectrum of specificities ranging from side-chain groups to an entire penicillin or cephalosporin molecule. In addition to such structural heterogeneity of allergenic determinants, IgE antibodies in the sera of different allergic subjects show heterogeneous recognition responses. Detailed immunochemical studies were carried out on the sera of penicillin-allergic subjects that showed selective and unexpected reactions with the frequently prescribed penicillin, amoxicillin. Antibodies from one subject reacted only with the amoxicilloyl determinant while IgE from another subject showed multiple reactivity with penicilloyl and penicillanyl determinants of different penicillins but not with the amoxicilloyl determinant. Quantitative hapten inhibition studies revealed that the combining sites of the former antibodies were complementary to amoxicillin in a form that permits binding to the hydroxyaminobenzyl side-chain and the thiazolidine ring carboxyl. These conditions are satisfied with the drug in the '-oyl' but not in the '-anyl' form which involves linkage through the 2-carboxyl of the thiazolidine ring. With the second serum, adsorption studies showed that the wide-ranging reactivity of IgE was due to a single population of antibodies that detected a common specificity on the different penicillins. Combining site studies revealed clear recognition of the benzyl portion of the side-chain of benzylpenicilloyl, benzylpenicillanyl, ampicilloyl, ampicillanyl and amoxicillanyl determinants when free antibody access to the side-chain was possible but little or no recognition of the ring hydroxyl of amoxicillin. Such uninhibited access may not occur, however, when amoxicillin is conjugated in the '-oyl' form since opening the beta-lactam ring allows increased flexibility and rotation of the molecule and the possibility of close association of the hydroxyaminobenzyl side-chain of amoxicillin with the linked peptide carrier. In such close steric association, H-bonding involving the ring hydroxyl and amino acids of the carrier may prevent antibody access to the side-chain region of the amoxicilloyl determinant.

Anaphylactic or anaphylactoid reactions in patients undergoing cardiac surgery.

OBJECTIVE: To examine the clinical features, treatment, and outcome of anaphylactic and anaphylactoid reactions during cardiac surgery. DESIGN: Retrospective descriptive study. SETTING: A specialized referral anesthetic allergy clinic at a university teaching hospital. PARTICIPANTS: Twenty-three cardiac surgical patients referred after reactions resembling anaphylaxis. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The database of the anesthetic allergy clinic was examined, and the data for patients who developed anaphylactic or anaphylactoid reactions were collated and summarized. Twenty-three cardiac surgical patients who experienced signs of anaphylactic or anaphylactoid reactions during anesthesia and surgery from 8 cardiac surgical centers in a major city were referred to the clinic. Cephalosporin antibiotics (30%) and gelatin solutions (Hemaccel) (26%) were the most common (56%) causes of the reactions. Most reactions occurred before the start of cardiopulmonary bypass. Although metaraminol was the first vasopressor used in 18 of 23 patients, it was not effective in 14 patients. Response to epinephrine was immediate and effective in 88% of cases. Rapid placement onto cardiopulmonary bypass facilitated a good outcome and permitted all but one operation to proceed as planned. No intraoperative or postoperative deaths were recorded. CONCLUSION: Of the anaphylactic and anaphylactoid reactions, 60% occurred before cardiopulmonary bypass, and these were caused by antibiotics and gelatin solution. The results from this limited database showed that cardiac surgery proceeded without complications after cardiovascular collapse caused by anaphylactic or anaphylactoid reactions. Rapid institution of cardiopulmonary bypass may be life-saving and should be considered.

Wake-promoting and sleep-suppressing actions of hypocretin (orexin): basal forebrain sites of action.

The hypocretins (orexins) are a newly identified peptide family comprised of two peptides, hypocretin-1 and hypocretin-2. Recent observations suggest an involvement of these peptides in the regulation of behavioral state. For example, these peptides are found in a variety of brain regions associated with the regulation of forebrain neuronal and behavioral activity states. Furthermore, when infused into the lateral ventricles in awake animals, hypocretin-1 elicits increased duration of waking beyond that observed in vehicle-treated animals. Previous studies have been limited to an examination of the sleep-wake effects of hypocretin-1 in awake animals. Currently, the sleep-wake effects of hypocretin-2 and the extent to which hypocretins can initiate waking in the sleeping animal remain unclear. To better characterize the wake-promoting actions of the hypocretins, the current studies examined the sleep-wake effects of varying doses (0.007, 0.07 and 0.7 nmol) of hypocretin-1 and hypocretin-2 when administered into sleeping rats (e.g. remote-controlled infusions). Infusions of hypocretin-1 and hypocretin-2 into the lateral ventricles elicited a short latency (0.7 nmol hypocretin-1; 93+/-30 s from the start of the 120-s infusion) increase in electroencephalographic, electromyographic, and behavioral indices of waking. These infusions also produced substantial decreases in slow-wave and rapid-eye movement sleep. Hypocretin-1 was more potent than hypocretin-2 in these actions. Interestingly, hypocretin-1 infused into the fourth ventricle elicited less robust waking which occurred with a longer latency than infusions into the lateral ventricles. These latter observations suggest a forebrain site of action participates in hypocretin-1-induced waking. Within the forebrain, a variety of basal forebrain structures, including the medial preoptic area, the medial septal area and the substantia innominata, receive a moderate hypocretin innervation. Therefore, additional studies examined the sleep-wake effects of bilateral hypocretin-1 infusions into these basal forebrain structures. Robust increases in waking were observed following infusions into, but not outside, the medial septal area, the medial preoptic area and the substantia innominata. These results indicate a potentially prominent role of hypocretins in sleep-wake regulation via actions within certain basal forebrain structures and are consistent with studies indicating a prominent role of hypocretins in sleep/arousal disorders.

Amylin infusion into rat nucleus accumbens potently depresses motor activity and ingestive behavior.

Amylin, a calcitonin gene-related peptide-like peptide coreleased with insulin, exerts anorexic effects on central administration. Because previous studies revealed dense amylin binding in the nucleus accumbens (Acb), we investigated the behavioral effects of amylin infusions (10, 30, and 100 ng/side) into Acb subregions. Intra-Acb shell amylin infusions decreased ambulation, rearing, feeding, and drinking in either food-deprived rats or water-deprived rats; motor activity was affected more potently than ingestive behavior. Moreover, intra-Acb shell amylin reduced motor activity in nondeprived rats tested in the absence of food or water, indicating that the expression of amylin's effects is independent of drive or proximal incentives. Intra-Acb core amylin infusions in water-deprived rats also decreased ambulation and water intake, although anterior Acb placements were associated with smaller motor effects, regardless of Acb subregion. In contrast to amylin's effects, intra-Acb shell infusions of orexin-A (50, 100, and 500 ng/side) had no effects on motor activity, feeding, or drinking. Hence the Acb may be a target for behavioral regulation by satiety-related peptides like amylin.

Studies on the mechanism of multiple drug allergies. Structural basis of drug recognition.

The multiple drug allergy syndrome, that is, allergic recognition of a variety of drugs that may be both pharmacologically and structurally different, has been little studied and, consequently, the underlying mechanism(s) is unknown. The molecular basis of drug recognition by IgE antibodies found in the sera of subjects exhibiting multiple allergic drug sensitivities was studied by direct binding and quantitative hapten inhibition assays in experiments employing a wide range of carefully selected drugs and other chemicals. Drug recognition was shown to be related to the presence of tertiary and quaternary mono-, di- and trialkyl amino groups, but only if the alkyl groups were 'small' viz., methyl or, perhaps, ethyl. Primary, secondary, and tertiary (with R = 'large' alkyl) groups showed no direct antibody binding or antibody inhibitory activities. Near-neighbour effects of amide and hydroxyl groups appeared to promote weaker antigenic recognition. Results indicate that the antibody recognition and clinical drug allergy spectra of at least some subjects with multiple drug allergies are due to wide ranging immunological cross-reactivities with drugs containing tertiary amino and quaternary ammonium groups which are present in many different pharmacologically active agents. Separate populations of antibodies to other non-cross reacting drugs, for example, beta-lactam antibiotics, may also be present in the sera of such subjects.

Structural determinants of antibiotic allergy.

Allergies to antibiotics, mainly the beta-lactam antibiotics (penicillins and cephalosporins), are a common, costly, and potentially dangerous clinical problem encountered in everyday practice. Although studies on the role of non-beta-lactam antibiotics in allergic diseases, particularly the development of specific diagnostic tests and the immunochemical identification of allergenic structures, have been too few and relatively superficial, the situation with the beta-lactam antibiotics is much more advanced. Good progress has been made in identifying the spectra of allergenic determinants recognized by IgE antibodies in the sera of subjects sensitized to penicillins and cephalosporins, and this is aiding the development of an appropriate battery of drug conjugates for use as diagnostic agents. Patient-sensitivity responses to the beta-lactam antibiotics are frequently heterogeneous, and this factor must be taken into account for any diagnostic strategy or future therapy with a penicillin or cephalosporin.

Chemistry of drug allergenicity.

Of the very large number and variety of drugs used in medicine, those that are frequently implicated in immediate allergic reactions are relatively small in number and include neuromuscular blocking drugs used in anaesthesia, beta-lactam antibiotics, some other antibacterial agents including broad-spectrum antibiotics and quinolones and, less often, some narcotics. Structure-activity and immunochemical investigations have been most numerous and detailed for neuromuscular blocking drugs and beta-lactams, particularly penicillins. For the former group of drugs, morphine is proving to be a useful agent for the in-vitro detection of clinically relevant neuromuscular blocking drug-- as well as morphine- and fentanyl-reactive IgE antibodies. The employment of so-called 'major' and 'minor' determinants for a range of different penicillins and cephalosporins has revealed previously unsuspected heterogeneity in patient recognition responses, and has reinforced findings on the allergenic importance of side-chain groups. Many reports have been published on anaphylaxis to chlorhexidine, and progress in identifying allergenic determinants is reviewed together with the still inadequately understood subject of IgE antibody recognition of quinolone antibacterial agents.

Fatal anaphylaxis following jack jumper ant sting in southern Tasmania.

The "jack jumper" ant (Myrmecia pilosula) is a major cause of anaphylaxis in Tasmania. We describe four deaths attributed to stings by this ant between 1980 and 1999. All victims were men aged 40 years or over with significant comorbidities; two were taking angiotensin-converting enzyme inhibitors, which may increase risk of severe anaphylaxis. Three victims had known ant-sting allergy, but only one carried adrenaline, which he did not use. Another believed he was protected by previous attempts at hyposensitisation with whole ant-body extract. There is potential to prevent deaths by careful education of people with known allergy, prescribing of adrenaline for auto-injection and development of an effective hyposensitisation therapy.

In vitro reactivity of penicilloyl and penicillanyl albumin and polylysine conjugates with IgE-antibody.

Penicilloylated (BPO) and penicillanylated (BPA) poly-L-lysine (PLL) and human serum albumin (HSA) were prepared and characterized by penamaldate assay and proton NMR spectroscopy. The conjugates were coupled to nitrocellulose (NC) discs and cyanogen bromide activated paper discs and their in vitro reactivities with serum IgE antibodies were examined. Results showed that on paper discs, 55.3 and 83% of the sera reacted with PLL conjugates of BPO and BPA, respectively, while 41.5 and 58.1% reacted with HSA conjugates. On NC discs, HSA conjugates gave better results, 75.6 and 70.7%, respectively for BPO and BPA, compared with 38.6 and 50%, respectively for the PLL conjugates. Overall, the BPA-PLL conjugate on paper discs proved to be the most reactive preparation. Addition of the BPO-PLL paper disc preparation detected more positive sera (85.1%) and we believe that the combined use of these two specificities offers the best test for the detection of penicillin-reactive IgE antibodies.

Reaction with, and fine structural recognition of polyamines by human IgE antibodies.

Human IgE antibodies from nine allergic subjects were found to react with poly-L-lysine (PLL) and other polyamines. Radioimmunoassay inhibition studies indicated that the two amino groups, but not the carboxyl, in lysine contributed to the antibody binding and 4-aminomethyl-1,8-octanediamine, a compound containing three primary amino groups, was a better inhibitor than compounds containing only two primary amino groups. Ethylamine showed weak but clear inhibition indicating that even a single amino group could bind to the antibody combining site. Substituted ethanolamine and quaternary ammonium compounds were well recognized by some sera but with others, substitution hampered recognition. Inhibition studies with compounds containing an amino and a carboxyl group at different distances revealed that an adjacent carboxyl group interfered with recognition of the amino group by some IgE antibodies. IgE binding to PLL was examined at different pHs and ionic strengths. Binding was greatest at pH 5-6 to 8 and decreased markedly outside this range. Ionic strengths higher than 0.3 M significantly diminished the binding. These results indicated that binding of specific antibody to polyamine was due to electrostatic interactions of positively charged amino groups in the polyamine with the antibody combining site. These results may be relevant to mechanisms underlying recognition of some allergens in some atopic conditions.

Anaphylaxis to chlorhexidine. Case report. Implication of immunoglobulin E antibodies and identification of an allergenic determinant.

BACKGROUND: There are many reports of allergic reactions, including anaphylaxis, following exposure to chlorhexidine. Reactions may occur via contact with the skin and mucous membranes or from catheters treated with the antibacterial agent. Apart from implicating chlorguanide in immunoglobulin (Ig) E antibody-binding studies on serum from an anaphylactic patient, little work has been done on the molecular basis of recognition of the agent in sensitive subjects. OBJECTIVES: The molecular basis of IgE-binding to chlorhexidine was closely examined with the view of defining its fine structural recognition features by antibodies from a subject who experienced anaphylaxis following contact with the antiseptic. METHODS: Tryptase determinations, different drug-solid phases, immunoassays and quantitative hapten inhibition studies with chlorhexidine and selected structural analogues were employed together with serum from the anaphylactic patient. Results were analysed to define the complete drug allergenic determinant and to identify the important structural features complementary to the IgE antibody combining sites. RESULTS: The subject's serum tryptase levels sampled after the reaction were elevated and employment of a chlorhexidine-EA Sepharose solid phase showed the presence of serum IgE antibodies to the drug. Lack of inhibition by 4-chlorophenol and other selected substituted phenyl compounds showed that the terminal groups at each end of the chlorhexidine molecule, alone, did not account for antibody recognition of the antibacterial agent. Although chlorguanide and alexidine, the structures of which each comprise part of the chlorhexidine molecule, showed significant inhibition of the binding of IgE antibodies to chlorhexidine, neither compound was as potent an inhibitor as chlorhexidine itself. Two molecules of chlorguanide make up the symmetrical molecule of chlorhexidine while the interior structure of alexidine (that is excluding the terminal 2-ethylhexyl groups) is identical to part of the chlorhexidine molecule. CONCLUSIONS: Taken together, for this patient, these results lead to the conclusion that the whole chlorhexidine molecule is complementary to the IgE antibody combining sites and that the 4-chlorophenol, biguanide and hexamethylene structures together comprise the allergenic determinant. Hence, like one of the trimethoprim determinants identified, but unlike most drug allergenic determinants identified so far, the chlorhexidine allergenic determinant identified here encompasses the entire molecule.

Immunoassays in the diagnosis of anaphylaxis to neuromuscular blocking drugs: the value of morphine for the detection of IgE antibodies in allergic subjects.

Radioimmunoassays (RIAs) for IgE antibodies to specific neuromuscular blocking drugs (NMBDs) are an important tool in the diagnosis of anaphylaxis during anaesthesia although they are performed in only a few laboratories throughout the world. NMBDs bind to antibodies by their substituted ammonium ions. We measured serum IgE antibodies to morphine and specific NMBDs in 347 patients with suspected anaphylaxis using blood specimens sent for mast cell tryptase assays. Morphine, which has a single substituted ammonium group, avidly binds in vitro to antibodies that react with NMBDs. The morphine RIA proved to be both a more sensitive and efficient test for the detection of IgE antibodies to NMBDs than the specific NMBD RIAs. We have adopted the morphine RIA in our laboratory in preference to the specific RIAs and predict that use of this single assay will become widespread for the in vitro diagnosis of allergic sensitivities to NMBDs.