Chapter 6
Metabolic Complications Of Antiretroviral Therapy

David H. Spach, MD

Overview   TOP

What is meant by metabolic complications of antiretroviral therapy (ART)?

Metabolic complications refers to a group of adverse drug reactions that have been associated with long-term use of antiretroviral drugs, which include:

• Lipid abnormalities
• Lipodystrophy
• Lactic acidosis
• Hyperglycemia
• Decreased bone mineral density

Each adverse reaction is more commonly associated with a specific class of antiretroviral drugs, and the agents within the class that cause the reactions do so with variable frequencies. In most cases, the pathophysiologic mechanism of the changes is unknown. The classes of drugs associated with each major adverse reaction are listed in Table 6-1.

What metabolic toxicities should you monitor for in patients taking ART?

Recommendations for monitoring patients for ART-related metabolic complications, listed in Table 6-2, are discussed in detail in the sections below.

Lipid Abnormalities   TOP

What antiretroviral medications adversely affect lipid levels?

Available data suggest that drugs in the protease inhibitor (PI) class have the greatest adverse effect on triglycerides, total cholesterol, and low-density lipoprotein (LDL) cholesterol levels. The mechanism remains unclear. Among the PIs, ritonavir (RTV) and ritonavir-boosted regimens appear to have the greatest impact on triglycerides and total cholesterol levels. Because some patients who receive ritonavir had no significant changes whereas others have dramatic increases, genetic predisposition may play a major role. The PI atazanavir (ATV) does not significantly affect lipid levels. The impact of nucleoside reverse transcriptase inhibitors (NRTIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs) on lipid levels has not been well defined, but the impact appears much less than changes associated with PIs. In 96-week data from a trial that compared stavudine (d4T) plus lamivudine (3TC) plus efavirenz (EFV) with tenofovir (TDF) plus lamivudine plus efavirenz, those patients in the stavudine arm had significantly higher cholesterol and triglyceride levels. The NNRTI nevirapine (NVP) has no adverse affect on lipids, and the changes with efavirenz are variable. Patients receiving PIs should undergo regular monitoring of lipid levels (see Table 6-2).

Do antiretroviral drugs cause an increase in cardiovascular disease?

Several isolated case reports initially suggested ART could lead to cardiovascular disease, including death from myocardial infarction, in HIV-infected patients. More recent aggregate data from over 20,000 patients in cohort studies indicate the risk related to ART is low and substantially lower than the risk of smoking (Friss-Moller, et al, 2003). In addition, in a large study that involved more than 36,000 veterans, investigators found the benefit of these drugs far outweighed the risks. Because cardiovascular disease may take 10-15 years to manifest, investigators will need long-term followup of individuals who have received ART to determine the long-term impact.

Should you treat abnormal lipid levels in HIV-infected persons?

Although prospective studies have not clearly defined the long-term adverse cardiovascular effects associated with hyperlipidemia in HIV-infected persons, abnormal lipid levels appear to pose the same long-term risks as have been well established in persons who do not have HIV infection and thus need to be managed appropriately (see Table 6-3). Accordingly, clinicians should address abnormal lipid levels and the individual patient risks, including prior cardiovascular events, smoking, hypertension, diabetes, family history, obesity, and baseline lipid levels. The potential interventions include 1) switching to a regimen less likely to cause abnormal lipids (if possible without sacrificing antiviral effectiveness), 2) implementing dietary changes, 3) using a lipid-lowering agent according to recommendations in Table 6-4, and 4) addressing other lifestyle habits that affect cardiovascular risk, such as smoking and exercise.

Table 6-4. Summary of National Cholesterol Education Program Treatment Recommendations Based on LDL Cholesterol*

Risk Category	Initiate Therapeutic Lifestyle Changes†	Consider Drug Therapy	LDL** cholesterol goal	Non-HDL** cholesterol goal
With CHD or CHD** risk equivalent (10-year risk >20%, noncoronary atheroslerotic vascular disease, or type 2 diabetes mellitus)	100 mg/dL ( 2.6 mmol/L)	130 mg/dL ( 3.4 mmol/L) 100¨C129 mg/dL (2.6¨C3.3 mmol/L): therapy optional	<100 mg/dL (<2.6 mmol/L)	<130 mg/dL (<3.4 mmol/L)
2 or more risk factors (10-year risk <20%)‡	130 mg/dL ( 3.4 mmol/L)	10-year risk of 10%¨C20%: 130 mg/dL ( 3.4 mmol/L) 10-year risk of <10%: ( 160 mg/dL ( 4.1 mmol/L)	<130 mg/dL (<3.4 mmol/L)	<160 mg/dL (<4.1 mmol/L)
0 or 1 risk factor‡	160 mg/dL ( 4.1 mmol/L)	190 mg/dL ( 4.9 mmol/L) 160¨C189 mg/dL (4.1¨C4.9 mmol/L): therapy optional	<160 mg/dL (<4.1 mmol/L)	<190 mg/dL (<4.9 mmol/L)

*	For patients with high triglyceride levels in whom LDL cholesterol cannot be measured, non-HDL cholesterol level (total cholesterol – HDL cholesterol) may be used as an approximation if 30 mg/dL (0.8 mmol/L) is added to the LDL cholesterol threshold. For those with triglyceride levels >200 mg/dL (2.3 mmol/L), the non-HDL cholesterol level is considered a secondary target of therapy and the goals of therapy are as indicated under the heading of non-HDL cholesterol goal.
†	Risk factors include cigarette smoking; hypertension (blood pressure 140/90 mm Hg or taking antihypertension drugs); HDL cholesterol level below 40 mg/dL (1.0 mmol/L); family history of premature CHD (in first-degree male relatives <55 years and first-degree female relatives <65 years); age (>45 years for men and >55 years for women). Risk factor equivalent: diabetes. If HDL cholesterol is over 60 mg/dL (1.6 mmol/L), subtract 1 risk factor from the total.
‡	Therapeutic lifestyle changes refer to reducing saturated fat and cholesterol intake; enhancing the reduction in LDL cholesterol level by the use of plant stanols/sterols and increased soluble fiber; weight reduction; and increased physical activity.
**	CHD, coronary heart disease; HDL, high-density lipoprotein; LDL, low-density lipoprotein; VLDL, very low-density lipoprotein.

What statins are recommended for treating patients on PIs?

Significant drug interactions may occur with PIs and lipid-lowering statins; for patients on PI-based ART, most experts consider pravastatin and atorvastatin as preferred statins and avoid using lovastatin or simvastatin. Initial therapy should consist of a low dose of either pravastatin (20 mg po qd) or atorvastatin (10 mg po qd), with monitoring of response to therapy and, if required, gradual and cautious increases in doses of the statin. Triglyceride levels in excess of 1000 mg/dL place the patient at risk for developing pancreatitis. Most experts recommend intervening when triglyceride levels exceed 500 mg/dL. Although dietary changes can improve triglyceride levels, most patients with PI-associated hypertriglyceridemia will require pharmacologic intervention. Patients with isolated hypertriglyceridemia should receive a fibric acid derivative, either gemfibrozil (600 mg po bid) or fenofibrate (200 mg po qd). For those who have high triglyceride and LDL cholesterol levels, a statin drug should be used first with the plan of adding a fibric acid derivative after 4 months if the response to the statin is suboptimal. Because both the statin drugs and the fibric acid derivatives can cause rhabdomyolysis, caution should be used if these medications are given concurrently. In patients with severe hypertriglyceridemia refractory to a fibric acid derivative, some experts would recommend a trial of adding fish oil supplements to the lipid-lowering regimen.

Does switching ART improve lipid abnormalities?

Although some antiretroviral medications clearly have a greater adverse impact than others on lipids, modifying the regimen in an attempt to improve the lipid profile is sometimes difficult, mainly because of the need to maintain antiretroviral efficacy. Examples of possible changes likely to improve lipid abnormalities include switching a PI to either nevirapine (NVP) or using the alternative PI atazanavir (ATV). Changing from a PI to efavirenz (EFV) has not produced consistent results. Preliminary data from one study has shown that patients who switched from stavudine (d4T) to tenofovir (TDF) had a significant improvement in cholesterol and triglyceride levels. Future work will better determine whether changes from one nucleoside to another will affect lipid levels.

Lypodystrophy   TOP

What is lipodystrophy?

Although lipodystrophy was first reported in the mid-1990's, investigators have not agreed on a standardized, objective definition for this disorder. Most researchers and clinicians loosely define lipodystrophy as any significant change in body morphology that does not result from either weight gain or weight loss. The general term lipodystrophy now typically includes 3 subsets of morphologic changes: generalized fat accumulation, focal fat accumulation, and fat atrophy. Fat accumulation most often occurs in the abdominal, breast, or dorsocervical region. Fat atrophy most often occurs as buccal fat pad atrophy (facial wasting) or subcutaneous fat wasting in the buttocks or extremities. Because a standardized definition for lipodystrophy is lacking, the incidence varies depending on the exact criteria investigators use to define lipodystrophy in their specific study. Tests for abnormalities in body fat distribution have included computed tomography (CT) scanning, magnetic resonance imaging (MRI), bioelectrical impedance analysis (BIA), DEXA (dual energy x-ray absorptiometry) scans, and anthropometric measurements. The CT and MRI tests are generally considered the most accurate, but not practical for routine screening purposes, primarily because of their high cost. Anthropometric measurements can estimate visceral adipose tissue and subcutaneous adipose tissue and can easily be performed in the clinic without major costs. Despite the many options available for measuring abnormalities in fat distribution, no technique has shown adequate sensitivity and specificity to recommend performing routinely.

What causes lipodystrophy in HIV-infected persons?

Despite intense investigation, the exact pathogenesis of lipodystrophy remains unclear. Initial reports linked PI use with lipodystrophy, but subsequent reports have identified lipodystrophy in patients who had never received a PI. Several studies have shown that the most important risk factors for development of lipodystrophy are a history of severe immune suppression (nadir CD4 count <100 cells/mm³), older age, prolonged use of antiretroviral drugs, and highly active antiretroviral therapy. Investigators have found that patients with lipodystrophy often have high insulin levels and evidence of insulin resistance, a finding that suggests insulin resistance is associated with lipodystrophy, but does not prove that insulin resistance causes lipodystrophy. Many clinicians have observed that fat accumulation is more often associated with PI-based therapy, whereas fat wasting has been most closely linked to NRTIs, particularly stavudine (d4T). In 96-week data from a trial that compared stavudine plus lamivudine (3TC) plus efavirenz (EFV) with tenofovir (TDF) plus lamivudine plus efavirenz, those patients in the stavudine arm had substantially higher rates of lipodystrophy.

Can fat redistribution be reversed?

First, it is important to evaluate the severity of the lipodystrophy, the degree to which the patient is bothered by the body changes, and how strongly the patient wants to try to reverse the lipodystrophy. Although fat redistribution does not appear to directly alter health outcome, many patients experience notable unfavorable changes in their phyical appearance that may affect their quality of life. Morever, these changes in body appearance may broadcast their HIV diagnosis. That lipodystrophy changes thus may even lead some to stop their antiretroviral medications. If lipodystrophy develops, there are 3 treatment options: 1) Switch therapy, meaning a substitution for the implicated drug. This usually involves a substitute for stavudine (d4T) if lipoatrophy has developed or a change to a non-PI-based regimen if fat accumulation has occurred. Initial results with switches showed limited success, and when there was a response it took a long time. More promising results were seen in a recent study in which replacing stavudine (d4T) with abacavir (ABC) or zidovudine (AZT) resulted in significant improvement after 48 weeks in patients with stavudine-induced lipoatrophy (McComsey, et al, 2004). 2) Drug therapy is another option. Metformin, thiazolidinediones, testosterone, other anabolic steroids, and growth hormone have been used with partial success with fat accumulation, but all have drawbacks and do not address the underlying lipoatrophy. 3) The third option is plastic surgery, which may be particularly useful for buccal fat atrophy or dorsothoracic fat accumulations; however, results have been highly variable, and these procedures are usually regarded as cosmetic surgery and not covered by insurance companies.

Lactic Acidosis   TOP

What are ART-related hyperlactatemia and lactic acidosis?

ART-related abnormalities of serum lactate levels (hyperlactatemia) range from asymptomatic hyperlactatemia to symptomatic hyperlactatemia with mild acidosis, to fulminant lactic acidosis, liver failure, and death. In addition, some patients develop hepatic steatosis. The development of fulminant lactic acidosis, although very rare, has clearly emerged as one of the most dreaded adverse effects associated with ART.

What antiretroviral drugs cause hyperlactatemia?

Hyperlactatemia and lactic acidosis result from abnormal mitochondrial toxicity caused by NRTIs that inhibit the critical enzyme mitochondrial DNA polymerase gamma. There is no evidence that NNRTIs or PIs cause mitochondrial toxicity or abnormalities in serum lactate levels. In vitro data and retrospective clinical data show that stavudine (d4T) and didanosine (ddI) are the most likely medications in the NRTI class to cause this complication, especially if used together. Zidovudine poses some risk but significantly less than either stavudine or didanosine. Tenofovir (TDF), abacavir (ABC), emtricitabine (FTC), and lamivudine (3TC) appear to pose the least risk of causing lactic acidosis. Identified risk factors, in addition to the use of NRTIs, include pregnancy, female gender, obesity, or concurrent treatment with ribavirin, hydroxyurea, or metformin.

How do you collect and interpret a serum lactate test?

The normal serum lactate level is <2 mmol/dL. Proper blood collection and appropriate transport are essential for obtaining an accurate result. The patient should not exercise for 24 hours prior to the test and should be well hydrated, and should rest for at least 5 minutes prior to the blood draw. The blood should be drawn without tourniquet and the patient should be instructed not to clench his or her fist. The sample should be submitted promptly for processing using a pre-chilled fluoride-oxalate tube transported on ice. The specimen should be processed within 4 hours after being drawn.
For interpretation, levels of 2-5 mmol/dL are often associated with no symptoms, levels of 5-10 mmol/dL are usually associated with symptoms that require discontinuation of NRTIs, and levels of >10 mmol/dL are associated with a fatality of >30% and require immediate intervention. Abnormal levels should usually be confirmed.

How do you diagnose lactic acidosis?

Routine monitoring of serum lactate levels in asymptomatic patients is not recommended (see Table 6-2), but obtaining a serum lactate level is critical if hyperlactatemia is suspected (see previous question for correct technique). Patients with mild increases in serum lactate levels generally do not have significant symptoms, and if symptoms are present, they are most likely nonspecific. With more severe increases in serum lactate levels, patients may have marked fatigue, nausea, anorexia, vomiting, abdominal pain, dyspnea, and hyperventilation. Although a chemistry panel may show a decreased serum bicarbonate level or increased anion gap level, some reports have documented patients with severe lactic acidosis who do not have abnormal serum bicarbonate or increased anion gap measurements. CT scan of the liver may show enlargement and fatty infiltration.

How do you manage severe hyperlactatemia or lactic acidosis?

Patients with severe hyperlactatemia or lactic acidosis should immediately discontinue ART (see Table 6-3). Seriously ill patients may require IV bicarbonate, mechanical ventilation, or dialysis. Most respond to drug withdrawal. Case reports have suggested improvement in lactic acidosis with use of compounds such as riboflavin, thiamine, L-carnitine, or co-enzyme Q, with the benefit hypothetically resulting from improvement in mitochondrial function; however, the use of these agents to prevent hyperlactatemia and lactic acidosis has not been studied. Unfortunately, even after discontinuing ART, recovery from lactic acidosis typically takes about 8 weeks, since regeneration of severely damaged mitochondria is a prolonged process.

Once a lactic acidosis episode is resolved, can a patient resume ART?

For those patients who recover from an episode of lactic acidosis, the optimal management of their subsequent ART remains unclear. For those patients who clearly need ART, the safest option would be to use a regimen that does not contain an NRTI, such as lopinavir plus ritonavir plus efavirenz (LPV/r + EFV), saquinavir plus ritonavir (SQV + RTV), or indinavir plus ritonavir plus efavirenz (IDV + RTV + EFV). Available data suggest tenofovir (TDF), lamivudine (3TC), emtricitabine (FTC), and abacavir (ABC) are the NRTIs least likely to cause severe hyperlactatemia or lactic acidosis. In a report of 17 patients who developed symptomatic hyperlactatemia while receiving stavudine (d4T), the patients were rechallenged with abacavir or zidovudine; none of the 17 had a recurrence of symptomatic hyperlactatemia. Nevertheless, providers should obtain expert consultation and also observe the patient closely when restarting a new regimen that includes one or more NRTIs in any patient with a history of lactic acidosis.

Other Metabolic Complications   TOP

Does ART cause hyperglycemia and diabetes?

Although several studies have shown that PIs can have a direct effect on glucose metabolism, predominantly by increasing insulin resistance, it remains unclear whether ART significantly increases the risk for developing diabetes mellitus. Available data would suggest that ART, particularly with PIs, likely causes a slightly increased risk of developing overt diabetes mellitus. Routine monitoring for hyperglycemia is recommended for any patient on a PI-based regimen (see Table 6-3). Studies of patients with hyperglycemia and insulin resistance have consistently shown that switching from a PI to either nevirapine (NVP), efavirenz (EFV), or abacavir (ABC) will significantly improve the hyperglycemia and insulin resistance. Nevertheless, further study is needed to better clarify the risk of a patient's developing diabetes mellitus while taking a PI and the long-term clinical benefit of switching from a PI to a regimen that causes less insulin resistance.

Does ART cause abnormalities in bone density?

Several retrospective reports have suggested that ART may cause decreases in bone mineral density and, rarely, avascular necrosis. Recently, the relationship between ART and decreases in bone mineral density has become very controversial and prospective studies are needed to resolve the issue. From a clinical perspective, avascular necrosis should be suspected when a patient complains of focal bone pain; either CT or MRI can confirm the diagnosis. Avascular necrosis most often involves the femoral or humeral head, can consist of necrosis at a single or multiple sites, does not respond to medical therapy, and typically requires surgical intervention (see Table 6-3). There are no data regarding modifying an ART regimen either to prevent avascular necrosis or to improve the condition once it has already developed.

• Metabolic complications include the long-term consequences of antiretroviral agents: lactic acidosis (due to NRTIs [nucleosides]), dyslipidemia (usually due to PIs), insulin resistance (usually due to PIs), fat redistribution (usually due to NRTIs and PIs).
• All PIs except atazanavir (ATV) are associated with variable increases in the LDL cholesterol and/or triglycerides.
• Cardiovascular risks of dyslipidemia associated with PI therapy are assumed to be the same as for persons without HIV infection; they are usually managed with lifestyle changes (smoking cessation, diet modifications, and exercise) and, if necessary, lipid-lowering drugs; if statins are used, pravastatin or atorvastatin are preferred to avoid drug interactions with the PIs.
• Patients receiving PIs should have blood lipids and glucose monitored at baseline, at 3-6 months and then at least annually, and more frequently depending on other risks and severity of abnormalities.
• ART is associated with fat redistribution, both fat accumulation (abdomen, breasts, dorsocervical) and fat wasting (buccal fat with face thinning, buttocks, and extremities). These changes can result in major unfavorable changes in physical appearance and can have a significant impact on quality of life.
• There are no effective treatments for reversing fat redistribution. Discontinuing or switching therapy has moderate effect at best and improvement requires a very long time; with face thinning the best results are with discontinuing stavudine (d4T) early.
• Lactic acidosis is a result of mitochondrial toxicity caused by prolonged use of NRTIs, primarily stavudine (d4T), didanosine (ddI) and to a lesser degree zidovudine (AZT).
• The usual symptoms of lactic acidosis are fatigue, abdominal pain, nausea, and weight loss; the usual laboratory finding is a serum lactate exceeding 5 mmol/dL. The main treatment is to discontinue the implicated drugs or switch to NRTIs that are less likely to cause this.
• Type 2 diabetes is an occasional complication of PI therapy due to insulin resistance. Monitoring should include fasting blood glucose at baseline and at 5-8 months with subsequent measurements depending on risk and prior results.
  

Suggested Resources   TOP

Bozzette SA, Ake CF, Tam HK, Chang SW, Louis TA. "Cardiovascular and cerebrovascular events in patients treated for human immunodeficiency virus infection." N Engl J Med. 2003;348:702-710.

Carr A, Cooper DA. "Adverse effects of antiretroviral therapy." Lancet. 2000;356:1423-1430.

Dube MP. "Disorders of glucose metabolism in patients infected with human immunodeficiency virus". Clin Infect Dis. 2000;31:1467-1475.

Dube MP, Stein JH, Aberg JA, Fichtenbaum CJ, et al: "Guidelines for the evaluation and management of dyslipidemia in human immunodeficiency virus-infected adults receiving antiretroviral therapy: Recommendations of the HIV Medicine Association of the Infectious Disease Society of America and the Adult AIDS Clinical Trials Group." Clin Infect Dis. 2003;37:613-627.

Moyle G, Carr A. "HIV-associated lipodystrophy, metabolic complications, and antiretroviral toxicities." HIV Clin Trials. 2002;3:89-98.

Moyle GJ, Datta D, Mandalia S, Morlese J, Asboe D, Gazzard BG. "Hyperlactataemia and lactic acidosis during antiretroviral therapy: relevance, reproducibility and possible risk factors." AIDS. 2002;16:1341-1349.

Orenstein R. "Presenting syndromes of human immunodeficiency virus." Mayo Clin Proc. 2002;77:1093-1102.

Smith KY. "Selected metabolic and morphologic complications associated with highly active antiretroviral therapy." J Infect Dis. 2002;185 Suppl 2:S123-127.

References   TOP

Friis-Moller N, Sabin CA, Weber R, et al. "Combination antiretroviral therapy and the risk of myocardial infarction". N Engl J Med. 2003;349:1993-2003.

McComsey GA, Ward DJ, Hessenthaler SM, et al. "Improvement in lipoatrophy associated with highly active antiretroviral therapy in human immunodeficiency virus-infected patients switched from stavudine to abacavir or zidovudine: the results of the TARHEEL study." Clin Infect Dis. 2004;38:263-270.

Schambelan M, Benson CA, Andrew Carr A, et al. "Management of metabolic complications associated with antiretroviral therapy for HIV-1 infection: Recommendations of an International AIDS Society-USA Panel." J Acquir Immune Defic Syndr. 2002; 31:257-275.

Cases   TOP

1. A 36-year-old HIV-infected man has received stavudine (d4T) plus lamivudine (3TC) plus indinavir (IDV) for approximately 4 years. This regimen was his first regimen and before starting therapy his HIV RNA was 59,000 copies/mL and his CD4 count was 34 cells/mm³. His antiviral and immunologic response has been excellent, with HIV RNA levels persistently less than 50 copies/mL and a CD4 count that has increased to 526 cells/mm³. In the past 9 months, however, he has developed hyperlipidemia, hyperglycemia, and body fat changes, most notably enlargement of his abdominal region and facial thinning. He has been very hesitant to change his regimen but now comes into the clinic to discuss this matter again.

Question: If he changes his antiretroviral regimen, will he likely continue to have excellent control of HIV?

Answer:
Since this patient has experienced excellent long-term viral suppression and this was his first regimen, it is highly likely that a switch from a PI to a NNRTI (efavirenz [EFV] or nevirapine [NVP]) would maintain continued viral suppression. Similarly, a change from one NRTI to another would likely have no adverse affect on HIV suppression. In patients who have previously developed resistance and are currently on a salvage regimen, changing a medication because of side effects can pose a much greater risk of not maintaining excellent virologic control.

Question: What improvements would he likely expect if he makes a change?

Answer:
Among the problems this patient has developed as a complication of ART, insulin resistance and hyperlipidemia are the most likely to improve with a regimen change. In particular, several studies have shown switching from a PI to either nevirapine, efavirenz, or abacavir (ABC) typically leads to significant improvement in hyperglycemia and insulin resistance. Improvements in lipids are most likely to occur if the PI is switched to either nevirapine or abacavir. Switching from one PI to the new PI atazanavir (ATV) may provide significant improvement in lipid abnormalities. Unfortunately, changing from a PI to an NNRTI has not produced reliable improvements in lipodystrophy. Changing from stavudine to either abacavir or tenofovir (TDF) may provide some improvement in lipodystrophy for some patients. Although tenofovir causes less lipodystrophy than stavudine, studies that examine the effect of changing stavudine to tenofovir have not been performed.

2. A 33-year-old woman on stavudine (d4T) plus didanosine (ddI) plus efavirenz (EFV) presents with severe fatigue. No obvious cause for the fatigue is discovered and 1 week later she returns with even worse fatigue. Serum chemistries now are notable for a bicarbonate of 17 mmol/L. A serum lactate level is drawn and a lactate level of 6.3 mmol/L is reported from the laboratory. The patient is not taking any other medications and is not taking any herbal preparations.

Question: Is the serum lactate level of 6.3 mmol/L concerning in this patient?

Answer:
Experts have stratified serum lactate levels based on the risk of developing complications from hyperlactatemia. Those with a serum lactate level of 2.1-5.0 mmol/L are considered to have mild hyperlactatemia, those with a serum lactate level of at least 5 mmol/L have serious hyperlactatemia, and those with a lactate level at least 5 mmol/L plus a bicarbonate level less than 20 mmol/L have lactic acidosis. Accordingly, the patient's serum lactate of 6.3 mmol/L (along with the serum bicarbonate of 17 mmol/L) is extremely concerning and suggests lactic acidosis, a potentially life-threatening problem.

Question: If lactic acidosis is suspected, how should the patient be managed?

Answer:
Because hyperlactatemia and lactic acidosis result from NRTI-induced mitochondrial toxicity, the first step in managing this problem is to immediately discontinue ART. Although several case reports have suggested improvement in lactic acidosis by using compounds such as riboflavin, thiamine, L-carnitine, or co-enzyme Q, supportive care remains the mainstay of therapy. After discontinuing ART, regeneration of severely damaged mitochondrial typically requires prolonged periods, and recovery from lactic acidosis can take several months. Following recovery, the optimal management of subsequent antiretroviral therapy remains unclear. Preliminary reports suggest changing the NRTIs (typically replacing stavudine) can safely be performed, but should be done with expert consultation.