Folate

Supplementation

By Kimberly

A. Stewart,

in Methotrexate-Treated Arthritis Patients

Allen H. Mackenzie,

Two hundred rheumatoid arthritis (RA) patients taking low dose methotrexate (MTX) were evaluated for adverse effects. During a mean follow up of 41.5 months, the mean cell volume (MCV) was elevated at some time during the course of treatment in 42 patients. The MCV was normal in the remaining 158 patients. One hundred ninety-eight patients were treated simultaneously with oral folic acid. With the exception of heartburn, which was seen more often in the high MCV group, there was no difference in the frequency of adverse effects attributable to MTX between groups. Severity of side effects and the

T

HE EFFICACY of weekly oral low-dose methotrexate (MTX), a dihydrofolate reductase inhibitor, in the treatment of rheumatoid arthritis (RA) has been well established.‘~4 The most common side effects of low-dose MTX in patients with RA include gastrointestinal toxicity, stomatitis, and alopecia.’ Bone marrow suppression is rare.h Megaloblastic anemia has been reported in patients taking MTX for treatment of psoriasis. Frequently, low serum or erythrocyte levels of folate were found in these patients.7-” Changes in folate-mediated metabolism of amino acids have been described in patients taking MTX for cytopenia has treatment of RA.” Although been reported in RA patients treated with low-dose MTX, its occurrence is generally rare and often associated with other risk factors such as advanced age, renal insufficiency, or prior

From The Cleveland Clinic Foundation, Department of Rheumatic and Immunologic Diseases, Cleveland, OH. Kimberly A. Stewart, MD: Fellow, Department of Rheumatic and Immunologic Diseases; Allen H. Mackenzie, MD: Head, Section on Clinical Rheumatology (Adult and Pediatric), Department of Rheumatic and Immunologic Diseases; John D. Clough, MD: Chairman, Department of Rheumatic and Immunologic Diseases; William S. Wilke, MD: Head, Section on Subspecialty Clinics, Department of Rheumatic and Immunologic Diseases. Address reprint requests to William S. Wilke, MD, The Cleveland Clinic Foundation, Department of Rheumatic and Immunologic Diseases/Desk A50, Cleveland, OH 44195-5028. Copyright 0 1991 by WB. Saunders Company 0049.017219112005-0006$5.0010 332

John D. Clough,

Rheumatoid and William

S. Wilke

frequency of MTX dose reduction and MTX discontinuation due to toxicity were also similar between groups. This analysis suggests that elevation of MCV in RA patients treated simultaneously with MTX and folate does not predict MTX toxicity. The authors also discuss the mechanism of action of MTX with regard to folate metabolism. Copyright o 1991 by W.B. Saunders Company INDEX WORDS: Folic acid; rheumatoid methotrexate; toxicity.

arthritis;

hematologic abnormalities.“,‘” Recently, Weinblatt and Fraser suggested that elevated mean corpuscular volume (MCV) may be a predictor of hematologic toxicity in RA patients receiving weekly low-dose MTX.14 We subscribe to this conclusion. Folic acid supplementation in RA patients treated with low-dose MTX has been shown to decrease MTX toxicity without affecting efficacy.” We report a series of 200 prospectively studied RA patients who were treated with low-dose MTX. All but two of these patients were also taking a folic acid supplement. But those patients developing a high MCV during treatment with MTX did not show an increased incidence of hematologic toxicity or any other side effect attributable to MTX with the exception of heartburn. We conclude that high MCV is not a clinical predictor of cytopenia or other MTX toxicity in RA patients taking low dose MTX who also receive folate supplementation.

PATIENTS AND METHODS

This was a prospective study of 200 patients taking weekly low-dose MTX (circa 8.5 mg weekly) for treatment of RA. Patients were seen regularly between 1986 and 1989 at The Cleveland Clinic Foundation. The mean follow up period was 41.5 months (range 13 to 48 months). Forty-two patients developed a high MCV (MCV greater than or equal to 100 fL) during this time period. All but two patients, one with a normal MCV and one with a high

Seminars in Arthrits and Rheumatism, Vol 20, No 5 (April), 1991: pp 332-338

333

FOLATE, RA, AND MTX

times normal and reflected moderately severe MTX toxicity. A clinical severity score of 4 was defined as the presence of cytopenia, documented infections, pulmonary toxicity, or death. Fisher’s exact test was used for statistical analysis between groups in comparing the frequency of side effects and side effect severity, and the frequency of side effects attributable to MTX resulting in dose decrease of MTX or discontinuation of MTX. Students’ c-tests were used to compare RA duration, mean years of MTX therapy, mean total and current dose of MTX, patient age, and folate dose between patients with normal and high MCVs. x’ Analysis was used to analyze rheumatoid factor status and gender proportion in these two groups.

MCV, received folic acid supplementation (circa 7.0 mg weekly). All patients in this study fulfilled the 1987 American Rheumatism Association criteria for RA.” All patients had been entered into a computer database of RA patients taking weekly oral low-dose MTX. This database contained patient gender, age, weight, and complete blood counts. Medical records of these patients were analyzed to ascertain duration of RA, cumulative MTX dose, weight, side effects of medications, folate dose, white blood cell count, hemoglobin, hematocrit, platelet count, aspartate amino transferase (AST), and creatinine. Concomitant medications were also recorded. High MCV was defined as an MCV greater than or equal to 100 fL and a normal MCV as more than 80 and less than 100 fL. Abnormal AST was defined as a value greater than 40 IU/L. Leukopenia was defined as a white blood cell count less than 4 K/UL and thrombocytopenia as a platelet count less than 150 WUL. Abnormal serum creatinine was defined as a value greater than 1.4 mgidL. Patients were routinely questioned about adverse effects from MTX at each clinical visit. The clinical impact of adverse effects were estimated by applying a clinical severity score.” A clinical severity score of 1, generally reflecting mild toxicity, was defined as the presence of alopecia, mild gastrointestinal side effects, such as nausea, anorexia, or heartburn, and pruritus or elevation AST less than two times normal. A clinical severity score of 2, corresponding to moderate toxicity, was defined as vomiting, diarrhea, stomatitis, or rash. A clinical severity score of 3 included AST of greater than two

Table

1: Clinical

Features

RESULTS

Patients developing high MCVs while receiving low-dose MTX and patients with normal MCVs were similar with regard to duration of RA, mean years of MTX therapy, mean total dose of MTX, mean current dose of MTX, mean age, mean folate dose, rheumatoid factor positivity, and gender proportion. Likewise, no statistical difference between these clinical markers were seen in patients developing side effects regardless of their MCV status (Table 1). The incidence (overall frequency during the entire period of study) of side effects occurring in the normal MCV group was .79 and that in the high MCV group was .81 (P = .W).Side effects occurring in the high MCV group included heartburn, nausea, diarrhea, increased AST, alopecia, stomatitis, thrombocytopenia, leukopenia, rectal ulceration, and herpes zoster. MTX toxicity in the normal MCV group in-

of RA Patients

With

Normal

and High

High MCV Total

MCVs Taking

MTX

Normal MCV

With Toxicity

Total

With Toxicity

P

No. Patients

42

27

156

88

Duration

13

14

15

15

> .l

10

11

9

10

>.I

Years

RA (yrs)

MTX

Total Dose MTX Weekly

(mg)

Dose MTX

1397

(mg)

Age brs) Weekly

Dose Folate (mg)

Weight

(kg)

Note. Mean values for each variable are listed.

1390

1482

1542

> .l

> .l

8

8

9

9

> .l

61

65

58

58

> .l

7

8

7

7

62

69

58

71

> .I > 1

334

STEWART ET AL

Table

Side Effects Occurring in Patients

2:

High MCVs

and Normal

With

Incidence

Incidence

High

Normal

MCV

MCV

Group

Group

P

Heartburn

,357

.146

.02

Nausea

,095

,184

.25

.095

.070

.53

Alopecia

,071

.I08

.77

Stomatitis

.071

,082

.99

Thrombocytopenia

.024

,013

.50

Leukopenia

,024

.063

.46

Rectal

,024

0

.23

Diarrhea

.024

,006

.38

Zoster

.024

0

Side Effect

Elevated

AST

Ulcer

Gastrointestinal Abdominal

Upset Pain

Pneumonia/Death* *Developed Note.

pneumonia

Incidence

occurring

in 1 of 42 patients who developed a high MCV while taking MTX and 2 of 158 patients with a normal MCV. This difference was not statistically significant (P = .46). In all patients, the leukopenia was mild (white blood cell count greater than 2.5 WUL). One of 42 patients with a high MCV developed thrombocytopenia in comparison to 10 of 158 patients in the normal MCV group. This difference was not significantly different (P = .50). All patients maintained a platelet count greater than 5 K/UL. Because of the nonspecific description of many of the gastrointestinal side effects, we defined mild gastrointestinal toxicity as heartburn, nausea, abdominal pain, and gastrointestinal upset. When patients with a high MCV and patients with a normal MCV were analyzed, the incidences of mild gastrointestinal toxicity were .45 and .44, respectively, not significantly different (P = .99). Side effect severity was analyzed as previously defined. There was no difference in side effects between high and normal MCV patients (Table 3). Most side effects were mild. All elevations were less than two times normal. These elevations were transient in all patients with the exception of one patient with a high MCV in whom the AST remained elevated for 22 months. The rate of MTX dose decrease and discontinuation for reasons attributed to side effects were similar (Tables 4 and 5). Two patients in the high MCV group required reduction of MTX dose due to toxicity (P = .68). It should be noted that in one patient in the normal MCV group the dose of MTX was lowered solely because of elevation of serum creatinine (not attributed to MTX) without overt signs of toxicity. One patient in the high MCV group and five patients in the normal MCV group required

MCVs

.38

0

,076

.75

0

,038

.35

0

,006

.38

and died.

is defined

as frequency

of any side effect

during the study period.

eluded heartburn, nausea, abdominal pain, gastrointestinal upset, stomatitis, alopecia, increased AST, leukopenia, thrombocytopenia, and pneumonia (Table 2). The only side effect which occurred statistically more frequently in the high MCV group was heartburn (P = .02). All but two patients, one with a high MCV and one with a normal MCV, were receiving folate supplementation. The patient who developed a high MCV did not develop any manifestations of MTX toxicity. The patient with a normal MCV developed gastrointestinal upset that eventually resulted in discontinuation of MTX. In these patients, hematologic toxicity did not occur more frequently in folate-supplemented patients with high MCVs. Leukopenia occurred Table

3:

Severity

of Side Effects Incidence

Severity Score

Definition

1

Alopecia,

mild

2

Vomiting,

diarrhea,

3

AST

4

Cytopenia,

Note. Incidence

> two

GI side effects,

times

stomatitis,

< two

times

rash

normal

infection,

is defined as the frequency

AST

pulmonary,

death

of the listed side effects occurring

normal

High MCV

Normal MCV

Group

Group

P

.77

.78

.82

.15

.ll

0

0

.56 -

.09

.I0

1 .oo

during the study period.

335

FOLATE. RA, AND MTX

Table 4: MTX Discontinuation High MCV Group

due to Toxicity

(1 patient)*

Diarrhea Zoster Nausea Normal

MCV Group

Stomatitis

(5 patients)

(12 patients)t

Alopecia

(2 patients)t

Gastrointestinal Heartburn

upset (1 patient)

with high serum

creatinine

(1 patient) P = .99 *One patient developed both stomatitls and alopecia Experienced

diarrhea, zoster, and nausea.

of MTX due to toxicity (P = .99). High serum creatinine has been identified as a risk factor for the development of MTX toxicity in previous studies.’ One patient in the high MCV group experienced elevated serum creatinine, nausea, and increased AST while taking MTX. Nine patients in the normal MCV group developed high serum creatinine, although only four of these patients manifested side effects (heartburn, alopecia, leukopenia). The incidence of high serum creatinine was similar between patients with normal and high MC’Vs (P = .69). discontinuation

DISCUSSION

Folate compounds are essential for purine and thymidylic acid synthesis. Failure to synthesize these compounds results in decreased DNA synthesis, which in turn causes reduced cell proliferation. Folate compounds exist intracelluTable 5: Dose Reduction due to MTX Toxicity High MCV Group Alopecia Nausea

(1 patient)*

Increased Normal

(2 patients)

(1 patient)

AST (1 patient)*

MCV Group

Alopecia

(7 patients)

(2 patients)

Stomatitis

(2 patients)

increased

AST (1 patient)

Diarrhea Increased

(1 patient) creatinine

without

overt toxicity

(1 patient) P =- 58 *One patient had nausea and elevated AST.

larly in a polyglutamate form.” The enzyme dihydrofolate reductase reduces these to tetrahydrofolate, the active form necessary for enzymatic reactions involving purine and thymidylate production. MTX is an antifolate compound used to treat a variety of neoplastic, dermal, and rheumatic conditions. It binds to and inhibits the action of dihydrofolate reductase. Increased levels of dihydrofolate and decreased levels of tetrahydrofolate result.‘x Inhibition of dihydrofolate reductase particularly reduces thymidylate synthesis.“‘” A folate analogue, MTX is metabolized to a polyglutamate form intracellularly. These polyglutamate forms of MTX dissociate from dihydrofolate reductase at a much slower rate than native MTX, potentiating the inhibition of dihydrofolate reductase.” In addition, although native MTX exists intracellularly for brief periods of time, longer intracellular retention occurs with polyglutamated MTX.“” Longer intracellular retention has been shown to potentiate dihydrofolate reductase inhibition. Longer duration of cell exposure determines higher intracellular MTX polyglutamate concentration. High concentrations of MTX polyglutamates are found in human breast cancer cells after 6 hours of exposure to greater than or equal to 2 ugmL of MTX.” In addition to purine and thymidylate synthesis, tetrahydrofolate is also required for the synthesis of certain proteins. Conversion of glycine to serine and of homocysteine to methionine requires tetrahydrofolate.‘” The antiproliferative effects of MTX are thought to be the mechanism of action in regard to antitumor effect. The mechanism of action of MTX in inflammatory arthritis is less clear?’ Inhibition of immunoglobulin (Ig) G and IgM synthesis, postulated to be secondary to MTX inhibition of methionine has been shown to inhibit the release of azurophil granules from neutrophiIs’“.” and to decrease interlcukin I activity.“’ Olsen, Callahan, and Pincus described decreased IgM rheumatoid factor synthesis by blood mononuclear cells in MTX-treated RA patients.3’ Delayed hypersensitivity is suppressed by MTX as well.” MTX may also

336

normalize suppressor and effector T cell subsets in RA.3’ Folate deficiency has been proposed as a mechanism of MTX toxicity.“,‘4-“7Prolonged lowdose MTX therapy has been shown to result in low erythrocyte folate levels.7338Decreased hepatic stores of folate have been described in patients taking low-dose MTX for RA.33.38Megaloblastic changes on bone marrow examination, suggestive of folate deficiency, have been seen in RA patients developing pancytopenia while taking MTX.6 Folinic acid (leucovorin), a reduced form of folate, repletes intracellular tetrahydrofolate and competes with MTX for entry into cells.26 Leucovorin has been shown to replete MTX induced depletion of hepatic folate stores in patients taking MTX for RA.35 In addition, improvement in stomatitis,39’4”cytopenia,14 and resolution of transaminase elevation41 due to low-dose MTX have occurred with leucovorin administration. However, efficacy of low-dose MTX in the treatment of RA may be compromised by concurrent leucovorin administration.4” Folic acid may be an alternative to leucovorin in regard to decreasing MTX toxicity without compromising the efficacy of this drug in the treatment of RA. Recently, Morgan et al studied the effect of folic acid supplementation in RA patients taking low-dose MTX in a placebo controlled, double-blind study.5 A significant decrease in MTX toxicity was seen in the folic acid group. Furthermore, a statistically significant increase in MCV occurred in patients not receiving folate supplementation. Efficacy of low-dose MTX for RA was not compromised by the addition of folate. Weinblatt and Fraser suggested that an increase in MCV may predict hematologic toxicity in RA patients taking low-dose MTX.14 Most patients who developed MTX-induced cytopenia had a MCV greater than 100 fL for at least 6 months prior to the onset of hematologic toxicity. Low red blood cell and serum folate levels also occurred in these patients, who did not receive folic acid supplementation. In our study comparing RA patients with high and normal MCVs taking MTX and folate, we found no difference in incidence of side effects

STEWART

ET AL

due to MTX between the two groups. Heartburn occurred more frequently in the high MCV group. However, when mild gastrointestinal side effects (nausea, heartburn, abdominal pain, and gastrointestinal distress) were compared, no difference was noted between patients with high and normal MCVs. Side effect severity was similar between the two groups. Patients developing high MCVs while taking MTX did not differ from those with normal MCVs in regard to age, weight, duration of disease or MTX therapy, mean cumulative or current MTX dose or folate dose. Furthermore, the frequency of high serum creatinine and of side effects occurring in conjunction with high serum creatinine were similar between the two groups. In contrast to Weinblatt and Fraser’s study, high MCV was not predictive of cytopenia in our study. Perhaps this is secondary to the addition of folate in our patient population that has long been a component of our clinical practice method.42 Conceivably this study has unmasked mechanisms of MTX action or toxicity other than those attributable to folate depletion. Our patients folate levels were not obtained. Serum folate levels are unreliable in patients taking MTX-because because the conventional Lactobacillus casei assay for folate is inhibited by small concentrations of MTX.43 The Cl index, lymphocyte folate, and red blood cell folate levels might have improved this study. However, intracellular folate levels have been Table 6: Prevalence of MTX Toxicity in Folate-Supplemented Y Nonfolate Supplemented

RA Patients

Folate

Nonfolate”

(%I

(%I

P-t

Nausea/vomiting

16.5

26.0

< .05

Diarrhea

1.0

14.8

< .05

Stomatitis

8.0

3.4

.50

.5

1.3

> .50

Herpes Zoster Elevated liver function tests

7.5

Cytopenia

7.0

*Data tThe

from

Segal

differences

la.3 5.0

and Wilke.42 were

compared

using

x2 analysis.

< .05 >.50

337

FOLATE, RA, AND MTX

shown to correlate inversely with increasing MCV’.‘” and we believe that the high MCV in our patients does indeed reflect low intracellular folate concentrations. The incidence of MTX toxicity in our patients was compared with a large group of patients who were not receiving folate derived from the A significant lower incidence of literature.“” diarrhea, elevated liver enzyme tests, nausea,

and vomiting was found in the folate treated group (Table 6). These results are consistent with the findings of Morgan and colleagues who demonstrated that folate supplementation decreases MTX toxicity.” ACKNOWLEDGMENTS The authors would like to thank Cynthia S. Scott for her technical assistance in preparing this manuscript.

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STEWART ET AL

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