Drug-induced thrombocytopenia

Detection of Drug-Induced Thrombocytopenia Signals in Children Using Routine Electronic Medical Records

Background: Drug-induced thrombocytopenia (DITP) is a severe adverse reaction and a significantly under-recognized clinical problem in children. However, for post-marketing pharmacovigilance purposes, detection of DITP signals is crucial. This study aimed to develop a signal detection model for DITP using the pediatric electronic medical records (EMR) data.

Methods: This study used the electronic medical records collected at Beijing Children’s Hospital between 2009 and 2020. A two-stage modeling method was developed to detect the signal of DITP. In the first stage, we calculated the crude incidence by mining cases of thrombocytopenia to select the potential suspected drugs. In the second stage, we constructed propensity score–matched retrospective cohorts of specific screened drugs from the first stage and estimated the odds ratio (OR) and 95% confidence interval (CI) using conditional logistic regression models. The novelty of the signal was assessed by current evidence.

Results: In the study, from a total of 839 drugs, 21 drugs were initially screened as potentially inducing thrombocytopenia. In total, we identified 18 positive DITP associations. Of these, potential DITP risk of nystatin (OR: 1.75, 95% CI: 1.37–2.22) and latamoxef sodium (OR: 1.61, 95% CI: 1.38–1.88) were two new DITP signals in both children and adults. Six associations between thrombocytopenia and drugs including imipenem (OR: 1.69, 95% CI: 1.16–2.45), teicoplanin (OR: 4.75, 95% CI: 3.33–6.78), fusidic acid (OR: 2.81, 95% CI: 2.06–3.86), ceftizoxime sodium (OR: 1.83, 95% CI: 1.36–2.45), ceftazidime (OR: 2.16, 95% CI: 1.58–2.95), and cefepime (OR: 5.06, 95% CI: 3.77–6.78) were considered as new signals in children.

Conclusion: This study developed a two-stage algorithm to detect safety signals of DITP and found eighteen positive signals of DITP, including six new signals in a pediatric population. This method is a promising tool for pharmacovigilance based on EMR data.

Entecavir-associated thrombocytopenia

Entecavir (ETV) is widely used in the treatment of hepatitis B, but there are only a few reports about entecavir-associated thrombocytopenia, and it is considered as an immediate response and inappropriate to continue the treatment with other nucleoside analogues. Now, we report the third case, and this case was delayed response and we switched to treatment with tenofovir (TDF). There was a 66-year-old female who was infected with hepatitis B virus (HBV). Her platelet count decreased from 111*10⁹/L to 3*10⁹/L and was prone to gum bleeding and skin ecchymosis after she received ETV treatment for 88 days. As a treatment option, ETV was replaced by TDF immediately, frequent platelets transfusions and thrombopoietin were applied for several days, daily prednisone of 50 mg was concomitantly taken, and then platelet count improved after 10 days. She was diagnosed with entecavir-associated thrombocytopenia after analysis of the temporal relationship and exclusion of other causes of thrombocytopenia by blood and bone marrow examinations. Our case suggested that the platelet count should be monitored regularly in patients during ETV treatment, and it may be a feasible option to choose TDF to maintain antiviral treatment when entecavir-associated thrombocytopenia occurs.

Thrombocytopenia and Critical Care Medicine

Platelet transfusions play an important role in the treatment of critically ill patients. Like any blood component, however, there are various aspects of platelet transfusion therapy that need be considered by the intensivist. These include the proper dose and type of platelet component to infuse, as well as the route and method of administration. Methods to reduce the volume of the transfused platelets, for example, must ensure that the infused platelets will be functional and viable, posttransfusion. Treatment and diagnosis of the HLA alloimmunized recipient can pose a serious challenge to the clinician and an obstacle to adequate platelet therapy. An ICU patient for whom an adequate posttransfusion platelet increment cannot be achieved is at great risk of suffering a fatal hemorrhage. The ICU physician should be aware of the techniques used in modern transfusion practice to avoid having to deal with this complication. Adverse reactions to platelet transfusion include not only serologic ones, but those related to febrile and allergic complications, as well as infectious complications. The latter group includes diseases caused by infection with cytomegalovirus, bacteria, and a cadre of viruses including HIV and hepatitis. The clinical approach to thrombocytopenia in the ICU will be covered in some detail in an effort to review many of the conditions associated with recipient thrombocytopenia, including ITP, TTP, dilutional thrombocytopenia, DIC, surgery, HELLP syndrome, and drug-induced thrombocytopenia. Unfortunately the treatment approaches traditionally used are not always derived from evidence-based studies. This review covers many of these topics in an attempt to help physicians become better able to manage thrombocytopenia in the ICU and thus provide the best transfusion therapy for their patients.

Thrombocytopenia and its Related Factors: A Hospital-based, Cross-sectional Study

Introduction: The objective of this study was to explore the association between thrombocytopenia and its related factors. Materials and Methods: This was a hospital-based, cross-sectional study. We retrospectively analysed the medical records of all patients who received periodic health examinations at a medical centre located at Taichung in Taiwan between 2000 and 2004. In all, 5585 subjects were included for further analysis. A complete physical examination, laboratory survey and abdominal ultrasonography were performed on each subject. The t-test, chi-square test and multivariate logistic regression analysis were used. Results: The subjects consisted of 3123 men (55.9%) and 2462 women (44.1%). The mean age was 49.4 ± 12.3 years (range, 20 to 87). The overall prevalence of thrombocytopenia was found to be 0.5%, higher in men than in women (0.6% vs 0.4%, P = 0.504). After controlling for the other covariates, multivariate logistic regression analysis exhibited that the factors significantly related to thrombocytopenia were increasing age (OR, 1.04; 95% CI, 1.004-1.08), anti-HCV positive (OR, 5.24; 95% CI, 2.08-13.20), liver cirrhosis (OR, 7.93; 95% CI, 2.28-27.62), and splenomegaly (OR, 18.86; 95% CI, 6.86-51.87). Conclusion: It is advisable to further check the hepatic status, if thrombocytopenia is noted. Key words: Hepatitis C, Liver cirrhosis, Splenomegaly, Thrombocytopenia

Drug-induced thrombocytopenia

Drug-induced thrombocytopenia was first described in the 19th century, yet our understanding of its pathogenesis continues to evolve. The list of drugs implicated in drug-induced thrombocytopenia is extensive and growing. Many, if not most, of these medications induce thrombocytopenia by immune mechanisms. Because the degree of thrombocytopenia can put patients at risk for serious bleeding, a prompt diagnosis is key to clinical management. The laboratory approach to diagnosing drug-induced thrombocytopenia is 2-pronged. First, nondrug causes of thrombocytopenia must be ruled out. Second, testing for drug-dependent platelet antibodies, available at specialized reference laboratories, often can identify the offending medication, although usually not in time for initial clinical management. Once a medication is suspected of causing thrombocytopenia, it must be discontinued promptly, and the patient should be monitored closely. Thrombocytopenia generally resolves quickly after offending medication withdrawal, and the prognosis of drug-induced thrombocytopenia is then excellent.

Fine specificity of drug-dependent antibodies reactive with a restricted domain of platelet GPIIIA

Drug-induced immune thrombocytopenia is caused by drug-dependent antibodies (DDAbs) that bind tightly to platelet glycoproteins only when drug is present. How drugs mediate this interaction is not yet resolved. Several studies indicate that sites recognized by DDAbs tend to cluster in specific structural domains, suggesting they may recognize a limited number of distinct epitopes. To address this issue, we characterized the binding sites for 16 quinine-dependent antibodies thought on the basis of preliminary studies to be possibly specific for a single epitope on glycoprotein IIIa (GPIIIa). Fourteen of the antibodies reacted with a 29-kDa GPIIIa fragment comprising only the GPIIIa hybrid and plextrin-semaphorin-integrin homology domains. However, studies with mutant GPIIIa and the blocking monoclonal antibody AP3 showed that the 14 DDAbs recognize at least 6 and possibly more distinct, but overlapping, structures involving GPIIIa residues 50 to 66. The findings suggest that even antibodies specific for restricted domains on a target glycoprotein may each have a slightly different fine specificity; ie, "unique" epitopes recognized by DDAbs may be rare or nonexistent. The observations are consistent with a recently proposed model in which drug reacts noncovalently with both target protein and antibody to promote binding of an otherwise nonreactive immunoglobulin.

Drug-induced immune thrombocytopenia

Thrombocytopenia can have several causes, including the use of certain drugs. The mechanism behind drug-induced thrombocytopenia is either a decrease in platelet production (bone marrow toxicity) or an increased destruction (immune-mediated thrombocytopenia). In addition, pseudothrombocytopenia, an in vitro effect, has to be distinguished from true drug-induced thrombocytopenia. This article reviews literature on drug-induced immune thrombocytopenia, with the exception of thrombo-haemorrhagic disorders such as thrombotic thrombocytopenic purpura and heparin-induced thrombocytopenia and thrombosis. A literature search in PubMed combined with a check of the reference lists of all the retrieved articles resulted in 108 articles relevant to the subject. The drug classes that are most often associated with drug-induced immune thrombocytopenia are cinchona alkaloid derivatives (quinine, quinidine), sulfonamides, NSAIDs, anticonvulsants, disease modifying antirheumatic drugs and diuretics. Several other drugs are occasionally described in case reports of thrombocytopenia; an updated review of these case reports can be found on the internet. A small number of epidemiological studies, differing largely in the methodology used, describe incidences in the magnitude of 10 cases per 1 000 000 inhabitants per year. No clear risk factors could be identified from these studies. The underlying mechanism of drug-induced immune thrombocytopenia is not completely clarified, but at least three different types of antibodies appear to play a role (hapten-dependent antibodies, drug-induced, platelet-reactive auto-antibodies and drug-dependent antibodies). Targets for drug-dependent antibodies are glycoproteins on the cell membrane of the platelets, such as glycoprotein (GP) Ib/IX and GPIIb/IIIa. Diagnosis of drug-induced immune thrombocytopenia may consist of identifying clinical symptoms (bruising, petechiae, bleeding), a careful evaluation of the causal relationship of the suspected causative drug, general laboratory investigation, such as total blood count and peripheral blood smear (to rule out pseudothrombocytopenia), and platelet serology tests. The sensitivity of these tests is dependent on factors such as the concentration of the drug in the test and the potential sensitisation of the patient by metabolites instead of the parent drug. Drug-induced immune thrombocytopenia can be treated by withholding the causative drug and, in severe cases associated with bleeding, by platelet transfusion. Although drug-induced thrombocytopenia is a relatively rare adverse drug reaction, its consequences may be severe. Therefore it is important to extend our knowledge on this subject. Future research should focus on the identification of potential risk factors, as well as the exact mechanism underlying drug-induced thrombocytopenia.

Frequency and management of thrombocytopenia with the glycoprotein IIb/IIIa receptor antagonists

Glycoprotein IIb/IIIa receptor antagonists (GPRAs) are widely used in the management of a variety of patients with acute coronary syndromes. Major adverse reactions to these agents include bleeding and thrombocytopenia. Immune mechanisms responsible for severe thrombocytopenia seen with GPRAs have been hypothesized for all 3 agents currently available in the United States, although specific laboratory tests are not available for use in routine practice. A review of published research for GPRA-induced thrombocytopenia (GIT) is provided. Although the incidence of severe GIT is relatively low, the implications for patients are potentially life threatening. Prompt recognition of severe thrombocytopenia is essential to facilitate the necessary care of patients. Treatment strategies include the modification of drug regimens and other interventions targeting the reduction of immediate bleeding risk and the provision of supportive care measures. A review of published research supporting the conservative use of corticosteroids and intravenous gamma globulin in this syndrome is provided. Clinicians identifying severe thrombocytopenia after GPRA exposure are encouraged to report these events, following national and institutional guidelines.

Teicoplanin-dependent antibodies: detection and characterization

There are only a few reports of thrombocytopenia associated with clinical doses of teicoplanin, a glycopeptide antibiotic used against Gram-positive bacteria. We investigated 39 patients receiving teicoplanin; 31 were thrombocytopenic with platelet counts between 1-105 x 10(9)/l and 8 were not thrombocytopenic. We identified 14 thrombocytopenic cases (45%) and two (25%) non-thrombocytopenic cases with IgG teicoplanin-dependent platelet-reactive antibodies. Use of glycoprotein (GP) capture enzyme-linked immunosorbent assay with platelets and GPIIb/IIIa transfected Chinese Hamster Ovary cells as well as flow cytometry with GP-deficient platelets indicated that the GPIIb/IIIa complex is a major target antigen of these antibodies.

Thrombocytopenia during valproic acid treatment in young patients with new-onset bipolar disorder

BACKGROUND

To evaluate whether valproic acid (VPA) can cause thrombocytopenia and impaired platelet function in young patients with new-onset bipolar disorder.

METHODS

The authors studied 25 new-onset young bipolar patients. Platelet count, platelet aggregation, platelet release, and bleeding time were evaluated before beginning VPA treatment and at least after 10 months of treatment. The control group consisted of 20 sex-matched and age-matched subjects. Patients were started on VPA at a dose of 250 to 750 mg/d, given in divided doses. Mean dosage of VPA was 1137.5 +/- 241.1 mg/d. Mean VPA total plasma concentration was 61.1 +/- 20 g/mL.

RESULTS

At baseline, no significant differences were observed for platelet count and function between the bipolar group and the control subjects. After 10 months, at the second evaluation, the platelet count was significantly lower in the bipolar patients than in the control subjects: 192.7 +/- 21.4/microL versus 289.8 +/- 23.9/microL; P < 0.0001. An important observation was that platelet counts were negatively correlated with VPA dose (r = -0.47; P = 0.05) and its plasma concentration (r = -0.50; P = 0.05). In the present study, the authors observed impairment in platelet release of ATP and aggregation that correlated with both VPA dosage and plasma levels. Bleeding times were also significantly longer in patients taking VPA compared with control subjects (P < 0.0001).

CONCLUSION

Thrombocytopenia can appear after a few months of therapy and with plasma VPA levels within the therapeutic range.

Treatment of drug-induced thrombocytopenia

Estimates on the incidence of drug-induced thrombocytopenia range 5-40% in patients receiving heparin to < 1% with other causative agents. Systematically assessing drug-induced thrombocytopenia through a series of steps, each step providing additional evidence that the suspected agent is the true cause of thrombocytopenia, is the best way to identify the causative agent. Databases exist to aid in identification of the causative agent. Knowing which medications may be causative agents as well as which are not known to cause drug-induced thrombocytopenia, the aetiologies of drug-induced thrombocytopenia, signs and symptoms of thrombocytopenia and strategies to treat thrombocytopenia associated with specific agents will provide the clinician with the necessary skills to make proper medical decisions.

Assessment of platelet numbers and morphology in the peripheral blood smear

Automated systems are currently in widespread use for the assessment of patients' complete blood counts. The evaluation of the peripheral blood smear, however, still constitutes a pivotal tool in the evaluation of patients with hematologic disorders. This article focuses on disorders affecting the number or morphology of platelets as assessed by evaluation of a peripheral blood smear and also outlines some of their important clinical findings.

Drug-induced and drug-dependent immune thrombocytopenias

Thrombocytopenia is a frequent comorbid condition in many in hospital patients. In some patients, drugs are the cause of low platelet counts. While cytotoxic effects of anti-tumor therapy are the most frequent cause, immune mechanisms should also be considered. This review addresses thrombocytopenias in four groups. Heparin-dependent thrombocytopenia (HIT), by far the most frequent drug-induced immune-mediated type of thrombocytopenia, has a unique pathogenesis and clinical consequences. HIT is a clinicopathological syndrome in which antibodies mostly directed against a multimolecular complex of platelet factor 4 and heparin cause paradoxical thromboembolic complications. The mechanisms through which heparin can enhance thrombin generation are discussed and treatment alternatives for affected patients are presented in detail. It is of primary importance to recognize these patients as early as possible and to substitute heparin with a compatible anticoagulatory drug, such as hirudin, danaparoid or argatroban. Patients seem to benefit from therapeutic doses of alternative treatment rather than from low-dose prophylactic doses. With the increasing use of glycoprotein (GP) IIb/IIIa inhibitors in patients with acute coronary syndromes, thrombocytopenias are increasingly recognized as an adverse effect of these drugs. Up to 4% of treated patients are affected. Most important, pseudothrombocytopenia, a laboratory artefact, is as frequent as real drug-induced thrombocytopenia and must be excluded before changes in treatment are considered. The pathogenesis of these thrombocytopenias is still debated; an immune mechanism involving preformed antibodies is likely. However, since these antibodies are also detectable in a high percentage of normal controls and of patients not developing thrombocytopenia, their impact is still unclear. Patients with real thrombocytopenia are at an increased risk of bleeding; treatment consists of cessation of the GP IIb/IIIa inhibitor and platelet transfusions in cases of severe hemorrhage. Classic immune thrombocytopenia can be induced by some drugs, e.g. gold, which trigger anti-platelet antibodies indistinguishable from platelet autoantibodies found in autoimmune thrombocytopenia. Drug-induced and drug-dependent immune thrombocytopenia is induced by antibodies recognizing an epitope on platelet GP formed after binding of a drug to a platelet glycoprotein. Still unresolved is whether antibody binding is the consequence of a conformational change of the antigen, the antibody, or both. These antibodies typically react with monomorphic epitopes on platelet GP, but only in the presence of the drug or a metabolite. Although several platelet GP have been identified as antibody target (GPIb/IX, GPV, GP IIb/IIIa), antibodies in an individual patient are highly specific for a single GP. Clinically, these patients present with very low platelet counts and acute, sometimes severe, hemorrhage. Treatment is restricted to withdrawal of the drug and symptomatic treatment of bleeding.

Can drugs cause autoimmune thrombocytopenic purpura?

A wide range of medications can cause life-threatening immune thrombocytopenia (ITP), hemolytic anemia, or neutropenia in sensitive individuals. The antibodies associated with these conditions usually require soluble drug to be present in order to react with the cell membrane glycoproteins for which they are specific. However, some patients make drug-independent antibodies (autoantibodies) as well. Occasionally, only autoantibodies are produced following exposure to a drug. Although drugs and other small molecules can become conjugated to proteins in vivo, which may induce an immune response, only fragmentary information is available to explain how exogenous substances sometimes perturb the immune system in such a way that antibodies capable of causing immune cytopenia are produced. Platelets are affected by drug-induced antibodies more often than any other blood element. For many drug-induced thrombocytopenias, the targeted membrane glycoproteins are readily accessible for laboratory investigation and methods for detecting the responsible antibodies are well developed. Techniques for studying cellular aspects of the immune response induced by drugs through in vitro manipulation of T and B lymphocytes are also advancing rapidly. Studies of drug-induced ITP may provide clues to the general mechanisms whereby drugs and other xenobiotics induce immune diseases. Clinicians should consider the possibility of an exogenous trigger in patients who present with apparent autoimmune thrombocytopenia.