Foscarnet and crystals in glomerular capillary lumens

A Systematic Review of the Reported Complications Related to Facial and Upper Extremity Vascularized Composite Allotransplantation

INTRODUCTION

Twenty three years after the first successful upper extremity transplantation, the role of vascularized composite allotransplantation (VCA) in the world of transplantation remains controversial. Face and upper extremity reconstruction via transplantation have become successful options for highly selected patients with severe tissue and functional deficit when conventional reconstructive options are no longer available. Despite clear benefit in these situations, VCA has a significant potential for complications that are more frequent when compared to visceral organ transplantation. This study intended to perform an updated systematic review on such complications.

MATERIALS AND METHODS

MEDLINE database via PubMed, Embase and Cochrane Library were searched. Face and upper extremity VCA performed between 1998 and 2021 were included in the study. Relevant media and press conferences reports were also included. Complications related to face and upper extremity VCA were recorded and reviewed including their clinical characteristics and complications.

RESULTS

One hundred fifteen patients underwent facial (43%) or upper extremity (57%) transplantation. Overall, the surgical complication rate was 23%. Acute and chronic rejection was identified in 89% and 11% of patients, respectively. Fifty eight percent of patients experienced opportunistic infection. Impaired glucose metabolism was the most common immunosuppression-related complication other than infection. Nineteen percent of patients ultimately experienced partial or complete allograft loss.

CONCLUSIONS

Complications related to VCA are a significant source of morbidity and potential mortality. Incidence of such complications is higher than previously reported and should be strongly emphasized in patient consent process. Strict patient selection criteria, complex preoperative evaluation, consideration of alternatives, and thorough disclosure to patients should be routinely performed prior to VCA indication.

Relationship between renal dysfunction and electrolyte abnormalities in hematopoietic stem cell transplant patients treated with foscarnet

This study aimed to investigate the relationship between renal dysfunction and electrolyte abnormalities, which are adverse events of foscarnet used for cytomegalovirus infection. Of the Ninety hematopoietic stem cell transplantation patients, 32 who met the selection criteria were enrolled in this retrospective study. The study patients were divided into two groups according to whether they developed renal dysfunction. The incidences of hypocalcemia, hypokalemia, and hypomagnesemia with an increase of grade 2 or higher in the renal dysfunction group were 45.5%, 18.2%, and 27.3%, respectively. Additionally, in the renal dysfunction group, a significant correlation was observed between creatinine and calcium (r = -0.458, p = 0.0244) and between creatinine and potassium (r = -0.520, p = 0.0092). This study shows that renal dysfunction and electrolyte abnormalities may be closely related in HSCT patients receiving foscarnet; thus, it is a report that may contribute to the safety of continuous foscarnet treatment.

Prediction of drug-induced kidney injury in drug discovery

Drug induced kidney injury is one of the leading causes of failure of drug development programs in the clinic. Early prediction of renal toxicity potential of drugs is crucial to the success of drug candidates in the clinic. The dynamic nature of the functioning of the kidney and the presence of drug uptake proteins introduce additional challenges in the prediction of renal injury caused by drugs. Renal injury due to drugs can be caused by a wide variety of mechanisms and can be broadly classified as toxic or obstructive. Several biomarkers are available for in vitro and in vivo detection of renal injury. In vitro static and dynamic (microfluidic) cellular models and preclinical models can provide valuable information regarding the toxicity potential of drugs. Differences in pharmacology and subsequent disconnect in biomarker response, differences in the expression of transporter and enzyme proteins between in vitro to in vivo systems and between preclinical species and humans are some of the limitations of current experimental models. The progress in microfluidic (kidney-on-chip) platforms in combination with the ability of 3-dimensional cell culture can help in addressing some of these issues in the future. Finally, newer in silico and computational techniques like physiologically based pharmacokinetic modeling and machine learning have demonstrated potential in assisting prediction of drug induced kidney injury.

Multiple Pathways for Pathological Calcification in the Human Body

Biomineralization of skeletal components (e.g., bone and teeth) is generally accepted to occur under strict cellular regulation, leading to mineral-organic composites with hierarchical structures and properties optimized for their designated function. Such cellular regulation includes promoting mineralization at desired sites as well as inhibiting mineralization in soft tissues and other undesirable locations. In contrast, pathological mineralization, with potentially harmful health effects, can occur as a result of tissue or metabolic abnormalities, disease, or implantation of certain biomaterials. This progress report defines mineralization pathway components and identifies the commonalities (and differences) between physiological (e.g., bone remodeling) and pathological calcification formation pathways, based, in part, upon the extent of cellular control within the system. These concepts are discussed in representative examples of calcium phosphate-based pathological mineralization in cancer (breast, thyroid, ovarian, and meningioma) and in cardiovascular disease. In-depth mechanistic understanding of pathological mineralization requires utilizing state-of-the-art materials science imaging and characterization techniques, focusing not only on the final deposits, but also on the earlier stages of crystal nucleation, growth, and aggregation. Such mechanistic understanding will further enable the use of pathological calcifications in diagnosis and prognosis, as well as possibly provide insights into preventative treatments for detrimental mineralization in disease.

Nephrotoxicity of Antimicrobials and Antibiotics

Medication-induced nephrotoxicity remains one of the most common causes of acute kidney injury (AKI) among hospitalized patients. Within the extensive group of medications associated with AKI, antibiotics and other antimicrobials are well recognized triggers of structural and functional renal impairment. Clinical manifestations range from mild forms of tubular injury to significant deterioration of kidney function requiring acute renal replacement therapy. Several mechanisms are described, although the most frequent are acute interstitial nephritis, acute tubular necrosis, intratubular crystal deposition, and proximal/distal tubulopathy with electrolyte wasting abnormalities. General risk factors for antimicrobial-induced AKI include pre-existing chronic kidney disease, and concomitant use of medication with nephrotoxic potential. Prevention and early recognition of AKI represent the standard approach to mitigate AKI and avoid morbidity.

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.

Foscarnet, zidovudine and dolutegravir combination efficacy and tolerability for late stage HIV salvage therapy: A case-series experience

Salvage therapy including foscarnet (PFA), zidovudine (ZDV) and an optimized background ART (OBT) has been shown to be effective in patients with advanced HIV infection, and no therapeutic options. Dolutegravir (DTG) may offer a more active combination. Objective was to describe efficacy and tolerability of PFA-ZDV-DTG containing regimen. In our cohort, we identified patients who: (i) had plasma HIV-1 RNA load (pVL) >50 c/ml (>100 for HIV-2) on combination ART (cART); (ii) had at least 1 PI/r, 1 NRTI, 1 NNRTI (for HIV-1), and at least 1 raltegravir resistance mutations; (iii) were naive to DTG; and (iv) initiated on a PFA-ZDV-DTG containing-regimen with 48 weeks (W48) of follow-up. Out of 5 patients, 2 were infected with HIV-2. At PFA-ZDV-DTG initiation, CD4 cell count was (/mm(3) ) of 64, 40, 10, in HIV-1, and 37, 199, in HIV-2 infected patients; and pVL (log10 c/ml) of 4.8, 5.1, 4.4, in HIV-1, and 3.6, 4.2, in HIV-2 infected patients, respectively. Median OBT genotypic sensitivity score was 1.5 [1-2]. PFA was discontinued in one patient, due to an acute renal failure. At W48, one HIV-1 infected patient had a pVL <50 c/ml and two <200 c/ml; the two HIV-2 infected patients had pVL >100 c/ml. No lack of treatment adherence was observed. In treatment experienced HIV-infected patients, failing cART and without other therapeutic options, a PFA-ZDV-DTG combination therapy could be effective. Renal adverse events should be monitored.

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.

Tubulointerstitial nephropathies in HIV-infected patients over the past 15 years: a clinico-pathological study

BACKGROUND AND OBJECTIVES

The therapy and outcome of HIV infection have dramatically changed over the last 15 years, resulting in a change in renal complications. This study analyzed the characteristics of HIV-infected patients and biopsy-proven tubulointerstitial nephropathies to define disease patterns and therapeutic implications.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A clinico-pathologic retrospective study of 59 consecutive renal biopsies showing predominant tubular and/or interstitial lesions in HIV-infected patients referred to the nephrology department between 1995 and 2011 was performed. HIV-associated nephropathy and vascular diseases were excluded from the study.

RESULTS

Tubulointerstitial nephropathies accounted for 26.6% of 222 native renal biopsies performed in HIV-infected patients. Two pathologic groups were analyzed, tubulopathy and interstitial nephritis, which represented 49% and 51% of tubulointerstitial nephropathies, respectively. Most patients presented with AKI (76.3%) and high-grade proteinuria (57.7%). Drug-related nephrotoxicity was the leading cause (52.5%). Alternative etiologies included infections (15.2%), dysimmune disorders (8.5%), malignancies (3.4%), and chronic (10.2%) and acute (10.2%) tubulointerstitial nephropathies of undetermined origin. Tubulopathy was strongly associated with antiretroviral drug toxicity (75.9%) and mostly caused by tenofovir (55.2%), which was associated with proximal tubular dysfunction (87.5%), overt Fanconi's syndrome (37.5%), and nephrogenic diabetes insipidus (12.5%). Interstitial nephritis was associated with a broader spectrum of pathologic lesions and etiologies.

CONCLUSIONS

In this series, tubulointerstitial nephropathies accounted for 26.6% of renal diseases in HIV-infected patients. Considering the therapeutic implications of diagnoses of drug toxicity, infection, and dysimmune syndromes, this study underscores the importance of monitoring renal parameters in HIV-infected patients and points to the relevance of kidney biopsy to allow an accurate diagnosis.

Shedding light on the chemical diversity of ectopic calcifications in kidney tissues: diagnostic and research aspects

In most industrialized countries, different epidemiologic studies show that chronic renal failure is dramatically increasing. Such major public health problem is a consequence of acquired systemic diseases such as type II diabetes, which is now the first cause for end stage renal failure. Furthermore, lithogenic diseases may also induce intratubular crystallization, which may finally result in end-stage renal failure (ESRF). Up to now, such rare diseases are often misdiagnosed. In this study, based on twenty four biopsies, we show that SR µFTIR (Synchrotron Radiation-µFourier transform infrared) spectroscopy constitutes a significant opportunity to characterize such pathological µcalcifications giving not only their chemical composition but also their spatial distribution in the tissues. This experimental approach offers new opportunities to the clinicians to describe at the cell level the physico-chemical processes leading to the formation of the pathological calcifications which lead to ESRF.

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.

Drug-induced glomerulopathies

Normal renal function depends upon an intact glomerular apparatus. Many drugs and chemicals are capable of damaging the glomerulus, causing its increased permeability to large molecules. Glomerular lesions are usually responsible for proteinuria and the nephrotic syndrome. This also holds true for the drug-induced glomerulopathies, of which membranous glomerulo-nephritis is the most frequent type of lesion encountered. Apart from this, several cases of different glomerular changes such as focal segmental glomerulosclerosis and crescentic glomerulonephritis have also been reported. The drug-induced glomerulopathies are probably immune mediated. This is, for instance, reflected in the fact that patients with drug-induced nephritic syndrome frequently have the HLA-B8 and DR3 antigens. In depth information is provided for the previously mentioned disorders.

Antiretroviral therapy and the kidney: balancing benefit and risk in patients with HIV infection

The widespread introduction of highly active antiretroviral therapy (HAART) has revolutionised the treatment and course of HIV infection, with complications of chronic HIV infection and HAART playing an increasingly important role in morbidity and mortality. Both HIV infection and HAART have been associated with the development of acute and chronic kidney disease. The incidence of HIV-associated nephropathy, the classic kidney disease of HIV, reached a plateau following the introduction of HAART, consistent with the pathogenic role of direct viral infection of the kidney. At the same time, antiretroviral agents and related therapies have demonstrated a range of nephrotoxic effects, including crystal-induced obstruction, lactic acidosis, tubular toxicity, interstitial nephritis and electrolyte abnormalities. This article reviews the impact of HAART on the epidemiology of HIV-related kidney disease, the potential nephrotoxicity of specific antiretroviral agents and related medications, and guidelines for monitoring kidney function in HAART-treated patients.

Antiviral Drug-Induced Nephrotoxicity

Drug-induced kidney injury is a major side effect in clinical practice, frequently leading to acute renal failure (ARF). It accounts for more than 2% to 15% of cases of ARF in patients admitted to the hospital or in the intensive care unit, respectively. The exact frequency of nephrotoxicity induced by antiviral drugs is difficult to determine. Antiviral drugs cause renal failure through a variety of mechanisms. Direct renal tubular toxicity has been described with a number of new medications with unique effects on epithelial cells of the kidney. These include cidofovir, adefovir dipivoxil, and tenofovir, as well as acyclovir. Additionally, crystal deposition in the kidney may promote the development of renal failure. Several different drugs have been described to induce crystal nephropathy, including acyclovir and the protease inhibitor indinavir. Renal injury associated with antiviral drugs involves diverse processes having effects on the renal transporters, as well as on tubule cells. In this article, we review the pathogenesis of antiviral drug-induced kidney injury, common nephrotoxic renal syndromes, and strategies for preventing kidney injury.

Drug-Induced Renal Failure in the ICU

Drug-induced renal failure is a frequent complication in the setting of ICU. Generally spoken pathomechanisms leading to drug-induced renal failure can be divided into hemodynamic effects, epithelial toxicity or crystalline nephropathy. The risk of drug-induced renal failure is increased by any form of hypovolemia (i.e. true hypovolemia or reduced effective circulating volume), older age, pre-existent renal impairment, and concomitant application of two or more nephrotoxins. This article reviews drugs most frequently responsible for renal failure in the ICU and discusses preventive measures. (Int J Artif Organs 2004; 27: 1034-42)

Foscarnet-induced crystalline glomerulonephritis with nephrotic syndrome and acute renal failure after kidney transplantation

Foscarnet nephrotoxicity has been reported to be associated with acute tubulointerstitial nephritis. Crystals in glomerular capillary lumens have also been observed in patients with acquired immunodeficiency syndrome who were treated with foscarnet for cytomegalovirus disease. We describe a kidney transplant recipient who developed a nephrotic syndrome with microscopic hematuria and nonoliguric acute renal failure within 15 days after starting foscarnet therapy for cytomegalovirus infection. A kidney biopsy specimen showed the presence of crystals in all glomeruli and in proximal tubules. Fourier transform infrared microscopy analysis demonstrated that crystals were made from several forms of foscarnet salts: mixed calcium and sodium salts, and unchanged trisodium foscarnet salts. Renal function and proteinuria spontaneously improved, and a second transplant biopsy performed 8 months after the first one revealed fibrotic organization of half of the glomeruli and of interstitial tissue, and crystal vanishing. We were thus able to provide proof of the possible precipitation of foscarnet in a transplanted kidney.

Irreversible glomerular lesions induced by crystal precipitation in a renal transplant after foscarnet therapy for cytomegalovirus infection

AIMS

Foscarnet is an antiviral agent used to treat cytomegalovirus infection in AIDS patients and in transplant recipients. In most cases, foscarnet induces reversible tubulo-interstitial lesions which can be avoided by correct hydration. We report the first case of crystal foscarnet precipitation within glomerular capillaries in a renal transplant.

METHODS AND RESULTS

The recipient, a 49-year-old man, developed a nephrotic syndrome with haematuria and an acute renal failure after foscarnet therapy for cytomegalovirus (CMV) infection. The polarization examination of the first graft biopsy revealed the presence of birefringent crystals within glomeruli and tubules. Infrared analysis attested to the presence of trisodium foscarnet salts and mixed sodium calcium salts coloured by Von Kossa's reaction. A second biopsy showed glomerular sclerosis, interstitial fibrosis, tubular atrophy and crystal vanishing. Polymerase chain reaction (PCR) in situ applied to this biopsy confirmed the diagnosis of cytomegalovirus infection.

CONCLUSIONS

These adverse effects might be the result of a toxic synergy between foscarnet and other drugs. In cases with crystalline precipitation, graft biopsy remains the best mean of diagnosis and follow-up of glomerular damage.

Antiviral efficacy and toxicity of ribavirin and foscarnet each given alone or in combination in the murine AIDS model

The antiviral efficacy and toxicity of ribavirin, foscarnet (PFA), and combinations of both drugs at two different doses have been evaluated in the murine AIDS (MAIDS) model. Our results clearly demonstrated that infected mice treated with ribavirin at 100 mg/ kg/day were protected against splenomegaly, lymphadenopathy, and hypergammaglobulinemia whereas PFA alone at 180 or 360 mg/kg/day did not afford any protection. Treatment with drug combinations showed protective effects similar to those observed with ribavirin alone. Hyperplasia and deorganization of the lymphoid architecture were noted in spleen and lymph nodes of infected mice compared to those of the uninfected group. However, treatment with ribavirin restored the lymphoid tissue architecture and reduced the emergence of germinal centers. Electron microscopic examination of renal cortex of animals treated with PFA at 360 mg/kg/day revealed clear mitochondrial necrosis (bursting of mitochondria) of the distal tubules and vacuolization of the proximal tubules which was more striking with combination therapy. Regarding hematotoxicity, PFA did not cause significant hematotoxicity at both doses, whereas ribavirin was hematotoxic at both doses (50 and 100 mg/kg/day), this toxicity being more evident at the higher dose. In conclusion, treatment with ribavirin showed clear efficacy against MAIDS whereas PFA had no efficacy. Furthermore, ribavirin treatment caused hematoxicity and PFA treatment resulted in nephrotoxicity.

Foscarnet alters antidiuretic hormone-mediated transport

Therapy with foscarnet is associated with acute renal failure. Prior studies have emphasized foscarnet's proximal tubular toxicity, but there have been isolated reports of foscarnet-induced nephrogenic diabetes insipidus. As a phosphate analog, foscarnet is a competitive inhibitor of NaPO4 cotransport. However, foscarnet's effect on antidiuretic hormone (ADH)-induced transport has not been previously investigated. We studied foscarnet's modulation of transport in the toad urinary bladder. Foscarnet at 10 microM to 10 mM did not alter basal water or urea flux. Urea transport induced by a maximal dose of ADH (24 mIU/ml) was inhibited by 0.1 to 5.0 mM foscarnet. In tissues challenged with 0.5 to 1.0 mIU of ADH per ml, 1.0 to 10 mM foscarnet increased water flow but did not alter urea flux. Foscarnet also increased water flow induced by 1.0 to 10 microM forskolin. In tissues pretreated with 10 microM naproxen, foscarnet did not alter water flow induced by 0.5 to 1.0 mIU of ADH per ml or forskolin. These results indicate that foscarnet stimulates water flow induced by 0.5 to 1.0 mIU of ADH per ml at a site proximal to that of the generation of cyclic AMP and inhibits urea flux induced by a maximal dose of ADH at a separate site. In humans, foscarnet nephrotoxicity is likely not limited to the proximal nephron, but extends to the collecting duct. Patients receiving foscarnet should be closely monitored for disorders of urinary concentration.

Foscarnet-Associated Penile Ulcerations

Objective:

To report a case of foscarnet-induced penile ulcerations and review literature related to this adverse effect.

Data Sources:

Case reports and review articles identified by a computerized search (MEDLINE) and manual search (Index Medicus).

Data Synthesis:

Foscarnet is a pyrophosphate analog antiviral agent that is approved by the Food and Drug Administration for treating cytomegalovirus retinitis in patients with AIDS. It also is used investigationally for other indications and human herpesvirus infections. Adverse effects include nephrotoxicity, anemia, ionized calcium abnormalities, and penile ulcerations. The majority of penile ulcers have developed within two weeks following initiation of foscarnet therapy with dosages of 180–200 mg/kg/d. Most cases required discontinuation of foscarnet to resolve the penile lesions. A postulated mechanism for this effect is inflammatory contact dermatitis from exposure to urine with elevated concentrations of foscarnet. We report a case of foscarnet-induced penile ulcerations that resolved after discontinuing this agent.

Conclusions:

Foscarnet can induce penile ulcerations. Increased awareness of this phenomenon, along with meticulous genital hygiene and urination practices, are required for its prevention.

Foscarnet. A review of its antiviral activity, pharmacokinetic properties and therapeutic use in immunocompromised patients with cytomegalovirus retinitis

The pyrophosphate analogue, foscarnet, selectively inhibits the DNA polymerase of human herpes viruses, including cytomegalovirus, and the reverse transcriptase of HIV. Viral replication is therefore prevented, but resumes when the drug is cleared from infected cells. In vitro, the combination of foscarnet and zidovudine (azidothymidine) has an additive effect against cytomegalovirus and acts synergistically against HIV. An improvement in cytomegalovirus retinitis is obtained in over 85% of affected AIDS patients during foscarnet induction therapy, but relapse usually occurs within a month of ceasing treatment. There is a similar duration of remission during maintenance therapy given for 5 days each week, but this can be extended 4- to 5-fold with daily administration of higher doses. In allograft recipients, progression of retinitis can be halted by foscarnet until immune function recovers and eradicates the virus. The incidence of acute renal failure, which is common during foscarnet therapy, may be reduced by dosage adjustment and adequate prehydration. Anaemia, phlebitis, nausea and vomiting, and disturbances in serum calcium and phosphate levels, perhaps resulting from uptake of foscarnet into bone or chelation with ionised calcium, have also been associated with administration of the drug. Cytomegalovirus retinitis is difficult to treat, with few therapeutic options available. Although treatment with foscarnet produces some severe adverse effects, with care these can be minimised, and the drug produces clinical improvement in a large proportion of patients; this is a highly encouraging finding at this stage in its development. Preliminary comparative data indicate that foscarnet and ganciclovir are similarly effective, but foscarnet may have some theoretical advantages in AIDS patients since it can be used in combination with zidovudine without potentiating myelosuppression.