Recombinant human erythropoietin
Erythropoietin is a glycosylated protein hormone and a hae-
matopoietic growth factor produced primarily in the kidneys.
Erythropoietin for clinical use is produced by recombinant
DNA technology and the name epoetin is often applied to
such material. Epoetin alfa (BAN, USAN. rINN), epoetin
beta (BAN. USAH. rINN). and epoetin gamma (BAN. rINN)
are recombinant human erythropoietins derived from a cloned
human erythropoietin gene. All have the same 165 amino acid
sequence but differ in the glycosylation pattern.
Erythropoietin Concentrated Solution (Ph. Eur.) is a clear or
slightly turbid colourless solution, containing 0.5 to 1O mg
per mL of glycoproteins indistinguishable from naturally oc-
curring erythropoietin in terms of amino acid sequence and
glycosylation pattern. It has a potency of not less than
100 000 units per mg of active substance. Store in airtight
containers below -20Β° and avoid repeated freezing and thaw-
ing.
Stability. Proprietary preparations of recombinant human
erythropoietin contain albumin or amino acids for stability
Administration to neonates may necessitate making very di-
lute solutions. A study of the stability of epoetin alfa in vari-
ous intravenous fluids' found that a minimum of 0.05%
protein was required to prevent loss of drug from solutions
containing epoetin alfa 0.1 units per mL. In another study,'
0.0125% albumin was sufficient to prevent loss of drug from
a solution containing epoetin alfa 100 units per mL.
Adverse Effects
Headache, hypertension, and seizures have been re-
ported in patients treated with recombinant human
erythropoietin particularly in those with poor renal
function. These adverse effects are probably associ-
ated with haemodynamic changes produced by the
increase in haematocrit. In patients with normal or
low blood pressure there have been isolated reports
of hypertensive crisis with encephalopathy-like
symptoms, including headache and confusion, and
generalised seizures. Other adverse effects include
thrombosis at vascular access sites and clotting in
the dialyser, transient increases in the platelet count,
flu-like symptoms including chills and myalgia, hy-
perkalaemia. and skin rashes. There have been rare
reports of anaphylactoid reactions.
Effects on the blood. Changes in rheological properties of
the blood following recombinant human erythropoietin ther-
apy were attributed to high red cell aggregation, possibly due
to hyperfibrogenaemia. The increased viscosity could have
contributed to an early kidney graft thrombosis in I patient:
and a delay in the onset of graft function in 7 others' Pre-
operative haemodilution was suggested as a possible solu-
tion.
Effects on electrolytes. Hyperkalaemia and hyperphos-
phataemia may occur in patients receiving recombinant hu-
man erythropoietin. However, hypophosphataemia has also
been reported in cirrhotic patients given erythropoietin prior
to autologous blood donation.
Effects on mental functions: visual hallucinations occurred
in 4 patients during treatment with recombinant human
erythropoietin, stopped when treatment was withdrawn, and
re-occurred in 2 patients when erythropoietin was reinstitut-
ed. Commenting on these and a further 7 cases the manu-
facturers considered the reaction to be extremely rare and that
the contribution of concurrent medication could not be dis-
counted. In two groups of dialysis patients treated with re-
combinant human erythropoietin. 15 of 134 and 2 of 103
experienced visual hallucinations.' Increasing age appeared
to be a risk factor.
Effects on the skin. Skin rashes may occur during treat-
ment with recombinant human erythropoietin.
Pseudoporphyria cutanea tarda, a photosensitivity disorder.
has been reported in two children undergoing peritoneal dial-
ysis and receiving erythropoietin. However, it was pointed
out that this disorder has occurred in adults undergoing dial-
ysis and the children were also receiving other potentially
photosensitising drugs.
Effects on the spleen. Aggravation of splenomegaly was
reported in 2 patients with myeloproliferative disorders fol-
lowing administration of recombinant human erythropoietin.
Splenic infarction has been reported in a patient with aplastic
anaemia treated with erythropoietin.
Effects of subcutaneous injections More pain at the injec-
tion site was experienced by patients given subcutaneous in-
iections of epoetin alfa than in those given epoetin beta. It
was suggested that different excipients in the two formula-
lions could be responsible.
Treatment of adverse effects. Venesection successfully
reduced the blood pressure in 4 patients with life-threatening
hypertension unresponsive to antihypertensive therapy asso-
ciated with recombinant human erythropoietin treatment.
Precautions
Recombinant human erythropoietin should be used
with caution in patients with hypertension, a history
of seizures, thrombocytosis, chronic liver failure,
ischaemic vascular disease, or in patients with ma-
lignant tumours. Hypertension should be well con-
trolled before treatment is started and the blood
pressure monitored during treatment.
Response to recombinant human erythropoietin
may be diminished by iron deficiency, infection or
inflammatory disorders, haemolysis, or aluminium
intoxication. Anaemia due to folic acid and vitamin
B-12 deficiencies should also be eliminated. Patients
undergoing dialysis may require increased doses of
heparin in view of the increase in packed cell vol-
ume.
Platelet counts and serum-potassium concentrations
should be monitored regularly.
Dosage must be carefully controlled to avoid too
fast an increase in haematocrit and recommended
haematocrit levels should not be exceeded due to the
increased risk of thrombotic events.
A study' involving 1233 patients undergoing haemodialysis
and suffering from congestive heart failure or ischaemic heart
disease found that erythropoietin in doses sufficient to in-
crease haematocrit to 42% (within the normal range) was as-
sociated with lack of benefit and a trend towards increased
mortality when compared with administration in doses suffi-
cient to maintain a lower haematocrit of around 30%. Howev-
er. these results are difficult to interpret, since within each
group, increased haematocrit was associated with lower mor-
tality, despite the between-group differences. The possibility
that intravenous iron supplementation might have contributed
lo these adverse results was considered, but commentators
suggested that until further data was available aiming for a
haematocrit of.33 to 36%. and using intravenous iron supple-
mentation where necessary, was still appropriated
Abuse. Comments on the dangers of the abuse of recom-
binant human erythropoietin by athletes as an alternative to
'blood doping'. Haematocrit may continue to rise for sev-
eral days after administration of recombinant human erythro-
poietin, possibly reaching dangerously high levels. Lack of
medical supervision and fluid loss during endurance events
increase the risk: of serious adverse consequences of changes
in blood viscosity produced by such misuse.
Resistance. Many factor's may contribute to a poor response
to recombinant human erythropoietin . A study In
patients with anaemia of end-stage renal disease found that
inadequate dialysis was associated with a reduced response to
erythropoietin treatment. Antibodies to recombinant human
erythropoietin have also been reported. Delayed clinical re-
sponse to recombinant human erythropoietin in I patient
could have been due to an inherited subclinical pyruvate ki-
nase deficiency.
Pharmacokinetics
Epoetin alfa and epoetin beta exhibit some differ-
ences in their pharmacokinetics, possibly due to dif-
ferences in glycosylation and in the formulation of
the commercial preparations.
Epoetin alfa is slowly and incompletely absorbed
following subcutaneous injection, and a bioavaila-
bility of about 10 to 50% relative to intravenous ad-
ministration has been reported. Peak concentrations
following epoetin alfa intravenously are attained
within 15 minutes, and within 4 to 24 hours follow-
ing subcutaneous injection.
The elimination half-life of epoetin alfa following
intravenous administration has been reported to be 4
to 16 hours in patients with chronic renal failure; the
half-life is generally less in patients with normal re-
nal function. An estimated elimination half-life of
about 24 hours has been reported for epoetin alfa
given subcutaneously.
Epoetin beta is similarly slowly and incompletely
absorbed after subcutaneous injection, and its abso-
lute bioavailability has been reported to be 23 to
42%. Peak serum concentrations are attained within
12 to 28 hours of subcutaneous administration. An
elimination half-life of 4 to 12 hours has been re-
ported following intravenous administration and a
terminal half-life of 13 to 28 hours following subcu-
taneous administration.
Uses and Administration
Erythropoietin is a glycosylated protein hormone
and a haematopoietic growth factor. It is secreted
primarily by the kidneys, although a small amount is
produced in extrarenal sites such as the liver. Eryth-
ropoietin regulates erythropoiesis by stimulating the
differentiation and proliferation of erythroid precur-
sors, stimulating the release of reticulocytes into the
circulation, and stimulating the synthesis of cellular
haemoglobin. The release of erythropoietin is pro-
moted by hypoxia or anaemia, and up to 1000 times
the normal serum-erythropoietin concentration may
be reached under these conditions; this response
may be impaired in some disease states such as
chronic renal failure. The haematological response
to erythropoietin is reduced if there is an inadequate
supply of iron.
Epoetin alfa and epoetin beta are recombinant hu-
man erythropoietins available for clinical use that
have the same pharmacological actions as endog-
enous erythropoietin. They are used in the manage-
ment of anaemia associated with chronic renal
failure in dialysis and predialysis patients; they may
reduce or obviate the need for blood transfusions in
these patients. They are also used in the manage-
ment of chemotherapy-induced anaemia in patients
with non-myeloid malignant disease. Epoetin alfa is
used in zidovudine-related anaemia in HIV-positive
patients. Epoetin beta is used in the management of
anaemia of prematurity. Recombinant human eryth-
ropoietin is also being evaluated in the management
of other types of normocytic-normochromic anae-
mias, including that associated with inflammatory
disorders such as rheumatoid arthritis. In all pa-
tients, iron status should be monitored and supple-
mentation provided if necessary.
Epoetin alfa and epoetin beta may also be used in
patients with moderate anaemia (but no iron defi-
ciency) before elective surgery to increase the yield
of blood collected for autologous blood transfusion.
Epoetin alfa may also be used in such patients to re-
duce the need for allogeneic blood transfusion.
In the management of anaemia of chronic renal
failure epoetin alfa or epoetin beta may be given
subcutaneously or intravenously. The aim of treat-
ment is to increase the haemoglobin concentration
to 10 to 12 g per 100 mL or to increase the haemat-
ocrit to 30 to 36%. The rate of rise in haemoglobin
should be gradual to minimise side-effects such as
hypertension; a rate not exceeding 2 g per 100 mL
per month is suggested.
Epoetin alfa may be given subcutaneously or by in-
travenous injection over at least I minute; slow in-
travenous injection over 5 minutes may be used in
patients who experience flu-like symptoms as side-
effects. In predialysis and haemodialysis patients, a
recommended initial dose of epoetin alfa is 50 inter-
national units per kg body-weight three times week-
ly; a higher initial dose of 50 to 100 units per kg
three times weekly has been suggested in the USA.
Doses may be increased at 4-week intervals in incre-
ments of 25 units per kg three times weekly until the
target is reached. In patients on peritoneal dialysis
an initial dose of 50 units per kg given subcutane-
ously twice a week is recommended. Once the target
is reached doses may need to be adjusted, and even
decreased, for maintenance therapy.
The usual total weekly maintenance dose of epoetin
alfa in predialysis patients is 50 to 100 units per kg
given in three divided doses, and in haemodialysis
patients it is about 100 to 300 units per kg given in
three divided doses. In predialysis patients a total
weekly dose of 600 units per kg should not be ex-
ceeded. In patients on peritoneal dialysis, the usual
total weekly maintenance dose is 50 to 100 units per
kg given subcutaneously in two divided doses.
In children, epoetin alfa may be given intravenously
to those on haemodialysis at an initial dose of 50
units per kg three times weekly. The dose may be
increased at 4-week intervals in increments of 25
units per kg three times weekly until a target haemo-
globin concentration of 9.5 to 11.0 g per 100 mL is
reached; the usual total weekly maintenance dose
given in three divided doses is: 225 to 450 units per
kg for those weighing less than 10 kg; 180 to 450
units per kg for those weighing 10 to 30 kg; and 90
to 300 units per kg for those weighing over 30 kg.
Epoetin beta is used similarly in the management of
anaemia of chronic renal failure in dialysis and pre-
dialysis patients. It may be given subcutaneously, by
intravenous injection over 2 minutes, or by intrave-
nous infusion. The following dosages may be used
in adults and children. For subcutaneous injection
the initial dose is 60 units per kg once a week for 4
weeks; alternatively, the total weekly dose may be
given in daily doses or three times a week. For intra-
venous injection the initial dose is 40 units per kg
three times weekly for 4 weeks. The dose may then
be increased to 80 units per kg three times weekly.
Thereafter the dose of epoetin beta may be increased
at 4-week intervals (if the increase in haemoglobin
concentration is less than I g per 100 mL per
month) in increments of 20 units per kg three times
weekly for intravenous administration or 60 units
per kg per week for subcutaneous administration un-
til a target haemoglobin concentration of 10 to 12 g
per 100 mL is reached. A total weekly dose of 720
units per kg of epoetin beta should not be exceeded.
For maintenance, the dose is halved initially and
then adjusted every I to 2 weeks according to re-
sponse.
In patients with non-myeloid malignant disease re-
ceiving chemotherapy, epoetin alfa or epoetin beta
may be given by subcutaneous injection in an initial
dose of 150 units per kg three times weekly. The
dose may be increased after 4 or 8 weeks, if neces-
sary, to 300 units per kg three times weekly. If the
response is still inadequate after 4 weeks at this
higher dose, treatment should be discontinued. As
an alternative regimen, the total weekly dose of epo-
etin beta may be divided into 7 daily doses.
To increase the yield of autologous blood, epoetin
alfa or epoetin beta may be used in conjunction with
iron supplementation. The dose depends on the vol-
ume of blood required for collection and on factors
such as the patient's whole blood volume and hae-
matocrit. Suggested regimens are: epoetin alfa 600
units per kg given intravenously twice a week start-
ing 3 weeks before surgery-, or up to 800 units per kg
of epoetin beta intravenously or up to 600 units per
kg subcutaneously twice a week for 4 weeks before
surgery. To reduce the need for allogeneic blood
transfusion epoetin alfa may be given in a dose of
600 units per kg subcutaneously once a week start-
ing 3 weeks before surgery or 300 units per kg sub-
cutaneously daily starting 10 days before surgery.
In HIV-positive patients on zidovudine therapy,
epoetin alfa may be beneficial if the endogenous se-
rum-erythropoietin concentration is 500 milliunits
or less per mL. Epoetin alfa is given by subcutane-
ous or intravenous injection in an initial dose of 100
units per kg three times weekly. The dose may be
increased every 4 to 8 weeks by 50 to 100 units per
kg three times weekly according to response. How-
ever, patients are unlikely to benefit from doses
above 300 units per kg three times weekly if lower
doses have failed to elicit a satisfactory response.
In the management of anaemia of prematurity
epoetin beta is given subcutaneously in a dose of
250 units per kg three times a week. Treatment
should be started as early as possible and continued
for six weeks.
Administration to neonates. Recombinant human eryth-
ropoietin may be given to neonates for anaemia of prematuri-
ty. It is usually administered by subcutaneous injection.
Administration by intravenous infusion in total parenteral nu-
trition solutions produced satisfactory results in a group of 20
neonates.
For a warning about diluting recombinant human erythropoi-
etin solutions, see under Stability, above.
Anaemias. Epoetins are used in normocytic-normochromic
anaemias associated with low endogenous erythro-
poietin concentrations.
Clinical studies have shown the effectiveness of epoetins in
correcting the anaemia of end-stage renal disease in patients
maintained by haemodialysis and they are also effective in
anaemia in predialysis patients. Although several factors con-
tribute to the aetiology of the anaemia, including blood loss
associated with dialysis, the main cause is inadequate produc-
tion of erythropoietin in the kidney. Consistently good results
have been obtained with epoetins not only for correction of
anaemia but also for quality of life and exercise capacity-
and for improvements in haemostatic' and cardiorespiratory
function. Guidelines have been introduced for their use in
chronic renal failure.
Over 90% of patients with renal anaemia respond to treatment
with epoetins. Many factors may contribute to a poor re-
sponse (see Precautions, above) and the patient should always
be investigated and the cause corrected where possible.
Epoetins may be administered intravenously or subcutane-
ously. Epoetin given subcutaneously produces lower but more
sustained plasma concentrations and comparative studies
have shown that total weekly maintenance doses are reduced
by between 23% and 52% with subcutaneous rather than in-
travenous administration. The subcutaneous route is thus
preferred especially in patients not on haemodialysis. The fre-
quency of administration may also be important in maximis-
ing the response to treatment, daily subcutaneous
administration has been reported to give a better response
than the same total weekly dose given two or three times a
week.l Intraperitoneal administration has also been investi-
gnted.
Epoetins are also used to treat anaemias from other causes.
Epoetins may be used for zidovudine-induced anaemia in
AIDS patients, in chemotherapy-induced anaemia in patients
with non-myeloid malignant disease, and in anaemia of pre-
maturity. Epoetins have a potential application for other
anaemias associated with impaired or insufficient erythropoi-
etin production, such as anaemias in infants with bronchopul-
monary dysplasia and infants with haemolytic disease of
the newborn, postpartum anaemia, and in arthritis
and inflammatory bowel disease.
Surgery. Concern over the safety of blood transfusions and
the need to conserve blood supplies has led to interest in
methods of reducing blood use in surgery. Recombinant hu-
man erythropoietin has been used to increase the number of
units harvested for autologous transfusion and to reduce
transfusion requirements. It has also been used as an alter-
native to blood transfusions.