Neurologic sequelae associated with foscarnet therapy

Neurological and Psychiatric Adverse Effects of Antimicrobials

Antimicrobials are a widely used class of medications, but several of them are associated with neurological and psychiatric side effects. The exact incidence of neurotoxicity with anti-infectives is unknown, although it is estimated to be < 1%. Neurotoxicity occurs with all classes of antimicrobials, such as antibiotics, antimycobacterials, antivirals, antifungals and antiretrovirals, with side effects ranging from headaches, anxiety and depression to confusion, delirium, psychosis, mania and seizures, among others. It is important to consider these possible side effects to prevent misdiagnosis or delayed treatment as drug withdrawal can be associated with reversibility in most cases. This article highlights the different neurotoxic effects of a range of antimicrobials, discusses proposed mechanisms of onset and offers general management recommendations. The effects of antibiotics on the gut microbiome and how they may ultimately affect cognition is also briefly examined.

Seizures in HIV: The case for special consideration

Purpose

This study aimed to determine the rate, cause and management of seizures in the context of potential ART–ASD interactions in a cohort of HIV + individuals.

Methods

Records of 604 HIV + patients were reviewed and those reporting epilepsy/seizure diagnosis were further evaluated.

Results

This cohort exhibited a seizure rate of 2.4%. HIV + patients treated for epilepsy displayed low serum ASD levels and failed to achieve seizure control. They were more likely to disengage from Neurology follow-up.

Conclusion

For HIV + patients presenting with seizures/epilepsy the ASD prescription and the provision of supplementary support services needs to be carefully considered.

•

ID and Neurology services should be involved in the evaluation and treatment of seizures in the context of HIV infection.

•

ART-ASD interactions could have been the cause of ineffective treatment and other poor outcomes in this small cohort.

•

In this group of patients it is important to apply published guidelines when it comes to making treatment decisions.

•

Counseling and supportive services need to be provided to ensure engagement with services and adherence to treatment.

Treatment of alpha and beta herpesvirus infections in solid organ transplant recipients

INTRODUCTION

Human herpesviruses frequently cause infections in solid organ transplant (SOT) recipients. Areas covered: We provide an overview of the clinical impact of alpha and beta herpesviruses and highlight the mechanisms of action, pharmacokinetics, clinical indications, and adverse effects of antiviral drugs for the management of herpes simplex virus, varicella zoster virus and cytomegalovirus. We comprehensively evaluated key clinical trials that led to drug approval, and served as the foundation for management guidelines. We further provide an update on investigational antiviral agents for alpha and beta herpesvirus infections after SOT. Expert commentary: The therapeutic armamentarium for herpes infections is limited by the emergence of drug resistance. There have been major efforts for discovery of new drugs against these viruses, but the results of early-phase clinical trials have been less than encouraging. We believe, however, that more antiviral drug options are needed given the adverse side effects associated with current antiviral agents, and the emergence of drug-resistant virus populations in SOT recipients. Likewise, optimized use and strategies are needed for existing and novel antiviral drugs against alpha and beta-herpesviruses in SOT recipients.

Varicella zoster: an update on current treatment options and future perspectives

INTRODUCTION

Varicella zoster virus is a highly contagious virus that causes a primary infection known as varicella (chickenpox) that may reactivate years later to cause herpes zoster (HZ or shingles). After shingles heal, patients may develop post-herpetic neuralgia (PHN), neuropathic pain syndrome that can cause significant suffering for years and is often refractory to treatment.

AREAS COVERED

The wide range of treatment and management options for varicella, HZ and PHN are reviewed and discussed. PubMed was the database used for the literature search.

EXPERT OPINION

Antiviral therapy effectively treats acute varicella and HZ. However, PHN is still difficult to manage, especially with the numerous treatment measures that do not work consistently in all patients. The best approach is to prevent the complication from occurring in the first place by preventing HZ with the HZ vaccine, which have decreased the burden of illness caused by VZ and the incidence of HZ. Unlike the varicella vaccine, the uptake for the HZ vaccine is very low and thereby more patients over the age of 50 years should be encouraged to receive the vaccine to reduce the risk of developing HZ. Initiating treatment with gabapentin and antiviral concomitantly as soon as the rash develops may reduce the severity of complications but there is a lack of data showing these medications preventing the development of PHN.

Antiviral drugs for viruses other than human immunodeficiency virus

Most viral diseases, with the exception of those caused by human immunodeficiency virus, are self-limited illnesses that do not require specific antiviral therapy. The currently available antiviral drugs target 3 main groups of viruses: herpes, hepatitis, and influenza viruses. With the exception of the antisense molecule fomivirsen, all antiherpes drugs inhibit viral replication by serving as competitive substrates for viral DNA polymerase. Drugs for the treatment of influenza inhibit the ion channel M(2) protein or the enzyme neuraminidase. Combination therapy with Interferon-α and ribavirin remains the backbone treatment for chronic hepatitis C; the addition of serine protease inhibitors improves the treatment outcome of patients infected with hepatitis C virus genotype 1. Chronic hepatitis B can be treated with interferon or a combination of nucleos(t)ide analogues. Notably, almost all the nucleos(t) ide analogues for the treatment of chronic hepatitis B possess anti-human immunodeficiency virus properties, and they inhibit replication of hepatitis B virus by serving as competitive substrates for its DNA polymerase. Some antiviral drugs possess multiple potential clinical applications, such as ribavirin for the treatment of chronic hepatitis C and respiratory syncytial virus and cidofovir for the treatment of cytomegalovirus and other DNA viruses. Drug resistance is an emerging threat to the clinical utility of antiviral drugs. The major mechanisms for drug resistance are mutations in the viral DNA polymerase gene or in genes that encode for the viral kinases required for the activation of certain drugs such as acyclovir and ganciclovir. Widespread antiviral resistance has limited the clinical utility of M(2) inhibitors for the prevention and treatment of influenza infections. This article provides an overview of clinically available antiviral drugs for the primary care physician, with a special focus on pharmacology, clinical uses, and adverse effects.

Ganciclovir-resistant cytomegalovirus encephalitis in a bone marrow transplant recipient

A 20-year-old patient, who received a bone marrow transplant in order to treat metachromatic leukodystrophy (MLD), succumbed to cytomegalovirus (CMV) encephalitis. After CMV viremia developed, the patient received ganciclovir, but he was switched to foscarnet when ganciclovir resistance was suspected. Foscarnet was discontinued because of concern about its potential central nervous system toxicity. Autopsy samples of brain and cerebrospinal fluid contained CMV DNA with a UL97 mutation (M460V) known to confer ganciclovir resistance. No foscarnet resistance mutations were found.

A double-blind placebo-controlled crossover trial of intravenous magnesium sulfate for foscarnet-induced ionized hypocalcemia and hypomagnesemia in patients with AIDS and cytomegalovirus infection

Foscarnet (trisodium phosphonoformate hexahydrate) is an antiviral agent used to treat cytomegalovirus disease in immunocompromised patients. One common side effect is acute ionized hypocalcemia and hypomagnesemia following intravenous administration. Foscarnet-induced ionized hypomagnesemia might contribute to ionized hypocalcemia by impairing excretion of preformed parathyroid hormone (PTH) or by producing target organ resistance. Prevention of ionized hypomagnesemia following foscarnet administration could blunt the development of ionized hypocalcemia. To determine whether intravenous magnesium ameliorates the decline in ionized calcium and/or magnesium following foscarnet infusions, MgSO(4) at doses of 1, 2, and 3 g was administered in a double-blind, placebo-controlled, randomized, crossover trial to 12 patients with AIDS and cytomegalovirus disease. Overall, increasing doses of MgSO(4) reduced or eliminated foscarnet-induced acute ionized hypomagnesemia. Supplementation, however, had no discernible effect on foscarnet-induced ionized hypocalcemia despite significant increases in serum PTH levels. No dose-related, clinically significant adverse events were found, suggesting that intravenous supplementation with up to 3 g of MgSO(4) was safe in this chronically ill population. Since parenteral MgSO(4) did not alter foscarnet-induced ionized hypocalcemia or symptoms associated with foscarnet, routine intravenous supplementation for patients with normal serum magnesium levels is not recommended during treatment with foscarnet.

Foscarnet-induced electrolyte abnormalities in a bone marrow transplant patient receiving parenteral nutrition

Cytomegalovirus (CMV) is a serious complication of immunosuppressed patients receiving bone marrow transplantation. Foscarnet, a pyrophosphate analog, has been used in the treatment of CMV infections. Renal impairment and electrolyte abnormalities are potential adverse reactions associated with the use of foscarnet. We report a case of significant electrolyte changes after initiation of foscarnet in a bone marrow transplant patient receiving parenteral nutrition.

HIV infection and seizures

New-onset seizures are frequent manifestations of central nervous system disorders in patients infected with human immunodeficiency virus (HIV). Seizures are more common in advanced stages of the disease, although they may occur early in the course of illness. In the majority of patients, seizures are of the generalised type. Status epilepticus is also frequent. Associated metabolic abnormalities increase the risk for status epilepticus. Cerebral mass lesions, cryptococcal meningitis, and HIV-encephalopathy are common causes of seizures. Phenytoin is the most commonly prescribed anticonvulsant in this situation, although several patients may experience hypersensitivity reactions. The prognosis of seizure disorders in HIV-infected patients depends upon the underlying cause.

Medical causes of seizures

Seizures are commonly encountered in patients who do not have epilepsy. Factors that may provoke such seizures include organ failure, electrolyte imbalance, medication and medication withdrawal, and hypersensitive encephalopathy. There is usually one underlying cause, which may be reversible in some patients. A full assessment should be done to rule out primary neurological disease. Treatment of seizures in medically ill patients is aimed at correction of the underlying cause with appropriate short-term anticonvulsant medication. Phenytoin is ineffective in the management of seizures secondary to alcohol withdrawal, and in those due to theophylline or isoniazid toxicity. Control of blood pressure is important in patients with renal failure and seizures. Non-convulsive status epilepticus should be considered in any patient with confusion or coma of unclear cause, and electroencephalography should be done at the earliest opportunity. Most ill patients with secondary seizures do not have epilepsy, and this should be explained to patients and their families. Only those patients with recurrent seizures and uncorrectable predisposing factors need long-term treatment with anticonvulsant medication.

Neurotoxicodynamics of the interaction between ciprofloxacin and foscarnet in mice

The potential for convulsions induced by the coadministration of ciprofloxacin (CPFX) and foscarnet (PFA) may be due not to a change in the distribution of CPFX to the brain but to a potential CPFX-induced inhibition of gamma-aminobutyric acid (GABA)-GABA(A) receptor binding in the presence of PFA.