Theophylline 5% Dextrose Injection Flexible
Theophylline should be used with extreme caution in patients with the following clinical conditions due to the increased risk of exacerbation of the concurrent condition:
Active peptic ulcer disease
Cardiac arrhythmias (not including bradyarrhythmias)
Conditions That Reduce Theophylline Clearance
There are several readily identifiable causes of reduced theophylline clearance. If the infusion rate is not appropriately reduced in the presence of these risk factors, severe and potentially fatal theophylline toxicity can occur. Careful consideration must be given to the benefits and risks of theophylline use and the need for more intensive monitoring of serum theophylline concentrations in patients with the following risk factors:
Neonates (term and premature)
Pediatric patients < 1 year
Elderly ( > 60 years)
Acute pulmonary edema
Congestive heart failure
Fever; ≥ 102° for 24 hours or more; or lesser temperature elevations for longer periods
Liver disease; cirrhosis, acute hepatitis
Reduced renal function in infants < 3 months of age
Sepsis with multi-organ failure
Cessation of Smoking
Adding a drug that inhibits theophylline metabolism (e.g., cimetidine, erythromycin, tacrine) or stopping a concurrently administered drug that enhances theophylline metabolism (e.g., carbamazepine, rifampin)(see PRECAUTIONS: DRUG INTERACTIONS, Table II).
When Signs or Symptoms of Theophylline Toxicity Are Present
Whenever a patient receiving theophylline develops nausea or vomiting, particularly repetitive vomiting, or other signs or symptoms consistent with theophylline toxicity (even if another cause may be suspected), the intravenous infusion should be stopped and a serum theophylline concentration measured immediately.
Increases in the dose of intravenous theophylline should not be made in response to an acute exacerbation of symptoms unless the steady-state serum theophylline concentration is < 10 mcg/mL.
As the rate of theophylline clearance may be dose-dependent (i.e., steady-state serum concentrations may increase disproportionately to the increase in dose), an increase in dose based upon a subtherapeutic serum concentration measurement should be conservative. In general, limiting infusion rate increases to about 25% of the previous infusion rate will reduce the risk of unintended excessive increases in serum theophylline concentration (see DOSAGE AND ADMINISTRATION, Table VI).
Careful consideration of the various interacting drugs and physiologic conditions that can alter theophylline clearance and require dosage adjustment should occur prior to initiation of theophylline therapy and prior to increases in theophylline dose (see WARNINGS).
Monitoring Serum Theophylline Concentrations
Serum theophylline concentration measurements are readily available and should be used to determine whether the dosage is appropriate. Specifically, the serum theophylline concentration should be measured as follows:
- Before making a dose increase to determine whether the serum concentration is subtherapeutic in a patient who continues to be symptomatic.
- Whenever signs or symptoms of theophylline toxicity are present.
- Whenever there is a new illness, worsening of an existing concurrent illness or a change in the patient's treatment regimen that may alter theophylline clearance (e.g., fever > 102°F sustained for ≥ 24 hours, hepatitis, or drugs listed in Table II are added or discontinued).
In patients who have received no theophylline in the previous 24 hours, a serum concentration should be measured 30 minutes after completion of the intravenous loading dose to determine whether the serum concentration is < 10 mcg/mL indicating the need for an additional loading dose, or > 20 mcg/mL indicating the need to delay starting the constant IV infusion. Once the infusion is begun, a second measurement should be obtained after one expected half life (e.g., approximately 4 hours in pediatric patients age 1 to 9 years and 8 hours in nonsmoking adults; See Table I for the expected half life in additional patient populations). The second measurement should be compared to the first to determine the direction in which the serum concentration has changed. The infusion rate can then be adjusted before steady state is reached in an attempt to prevent an excessive or subtherapeutic theophylline concentration from being achieved.
If a patient has received theophylline in the previous 24 hours, the serum concentration should be measured before administering an intravenous loading dose to make sure that it is safe to do so. If a loading dose is not indicated (i.e., the serum theophylline concentration is ≥ 10 mcg/mL), a second measurement should be obtained as above at the appropriate time after starting the intravenous infusion. If, on the other hand, a loading dose is indicated (see DOSAGE AND ADMINISTRATION for guidance on selection of the appropriate loading dose), a second blood sample should be obtained after the loading dose and a third sample should be obtained one expected half life after starting the constant infusion to determine the direction in which the serum concentration has changed.
Once the above procedures related to initiation of intravenous theophylline infusion have been completed, subsequent serum samples for determination of theophylline concentration should be obtained at 24-hour intervals for the duration of the infusion. The theophylline infusion rate should be increased or decreased as appropriate based on the serum theophylline levels.
When signs or symptoms of theophylline toxicity are present, the intravenous infusion should be stopped and a serum sample for theophylline concentration should be obtained as soon as possible, analyzed immediately, and the result reported to the clinician without delay. In patients in whom decreased serum protein binding is suspected (e.g., cirrhosis, women during the third trimester of pregnancy), the concentration of unbound theophylline should be measured and the dosage adjusted to achieve an unbound concentration of 6-12 mcg/mL.
Saliva concentrations of theophylline cannot be used reliably to adjust dosage without special techniques.
Effects on Laboratory Tests
As a result of its pharmacological effects, theophylline at serum concentrations within the 10-20 mcg/mL range modestly increases plasma glucose (from a mean of 88 mg% to 98 mg%), uric acid (from a mean of 4 mg/dl to 6 mg/dl), free fatty acids (from a mean of 451 μEq/l to 800 μEq/l), total cholesterol (from a mean of 140 vs 160 mg/dl), HDL (from a mean of 36 to 50 mg/dl), HDL/LDL ratio (from a mean of 0.5 to 0.7), and urinary free cortisol excretion (from a mean of 44 to 63 mcg/24 hr). Theophylline at serum concentrations within the 10-20 mcg/mL range may also transiently decrease serum concentrations of triiodothyronine (144 before, 131 after one week and 142 ng/dl after 4 weeks of theophylline). The clinical importance of these changes should be weighed against the potential therapeutic benefit of theophylline in individual patients.
Carcinogenesis, Mutagenesis, and Impairment of Fertility
Long term carcinogenicity studies have been carried out in mice (oral doses 30 - 150 mg/kg) and rats (oral doses 5 - 75 mg/kg). Results are pending.
Theophylline has been studied in Ames salmonella, in vivo and in vitrocytogenetics, micronucleus and Chinese hamster ovary test systems and has not been shown to be genotoxic.
In a 14 week continuous breeding study, theophylline, administered to mating pairs of B6C3F1 mice at oral doses of 120, 270 and
500 mg/kg (approximately 1 - 3 times the human dose on a mg/m² basis) impaired fertility, as evidenced by decreases in the number of live pups per litter, decreases in the mean number of litters per fertile pair, and increases in the gestation period at the high dose as well as decreases in the proportion of pups born alive at the mid and high dose. In 13 week toxicity studies, theophylline was administered to F344 rats and B6C3F1 mice at oral doses of 40 - 300 mg/kg (approximately 2 times the human dose on a mg/m²basis). At the high dose, systemic toxicity was observed in both species including decreases in testicular weight.
Pregnancy Category C
There are no adequate and well-controlled studies in pregnant women. In animal reproduction studies, maternal doses of theophylline less than one to two times the recommended oral dose in humans caused fetal harm, including fetal malformations. Asthma is a serious and potentially life-threatening condition. Poorly controlled asthma during pregnancy is associated with adverse outcomes for mother and fetus. Theophylline should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Population-based studies and post-marketing adverse event reporting of theophylline used during human pregnancy have not demonstrated an increased risk of major congenital anomalies. However, most studies were not large enough to detect a less than two fold increase in risk for congenital anomalies. Post-marketing data are reported voluntarily and do not always reliably estimate the frequency of particular adverse outcomes.
In animal reproduction studies, theophylline produced teratogenic effects when pregnant mice, rats and rabbits were dosed during the period of organogenesis.
In mice, a single intraperitoneal dose at and above 100 mg/kg (approximately equal to the maximum recommended oral dose for adults on a mg/m² basis) produced a cleft palate and digital abnormalities. Micromelia, micrognathia, club foot, subcutaneous hematoma, open eyelids, and embryolethality were observed at doses approximately 2 times the maximum recommended oral dose for adults on a mg/m² basis.
In rats dosed from conception through organogenesis, an oral dose of 150 mg/kg/day (approximately 2 times the maximum recommended oral dose for adults on a mg/m² basis) produced digital abnormalities. Embryolethality occurred at a subcutaneous dose of 200 mg/kg/day (approximately 4 times the maximum recommended oral dose for adults on a mg/m² basis). In rabbits dosed intravenously throughout organogenesis with 60 mg/kg/day (approximately 2 times the maximum recommended oral dose for adults on a mg/m² basis), caused cleft palate and was embryolethal. This dose was maternally toxic as one doe died and clinical signs of toxicity occurred in others. Doses at and above 15 mg/kg/day (less than the maximum recommended oral dose for adults on a mg/m²basis) increased the incidence of skeletal variations.
Theophylline is excreted into breast milk and may cause irritability or other signs of mild toxicity in nursing human infants. The concentration of theophylline in breast milk is about equivalent to the maternal serum concentration. An infant ingesting a liter of breast milk containing 10-20 mcg/mL of theophylline per day is likely to receive 10-20 mg of theophylline per day. Serious adverse effects in the infant are unlikely unless the mother has toxic serum theophylline concentrations.
Theophylline is safe and effective for the approved indications in pediatric patients (see INDICATIONS AND USAGE). The constant infusion rate of intravenous theophylline must be selected with caution in pediatric patients since the rate of theophylline clearance is highly variable across the age range of neonates to adolescents (see CLINICAL PHARMACOLOGY, Table I, WARNINGS, and DOSAGE AND ADMINISTRATION, Table V). Due to the immaturity of theophylline metabolic pathways in children under the age of one year, particular attention to dosage selection and frequent monitoring of serum theophylline concentrations are required when theophylline is prescribed to pediatric patients in this age group.
Elderly patients are at significantly greater risk of experiencing serious toxicity from theophylline than younger patients due to pharmacokinetic and pharmacodynamic changes associated with aging. Theophylline clearance is reduced in patients greater than 60 years of age, resulting in increased serum theophylline concentrations in response to a given theophylline infusion rate. Protein binding may be decreased in the elderly resulting in a larger proportion of the total serum theophylline concentration in the pharmacologically active unbound form. Elderly patients also appear to be more sensitive to the toxic effects of theophylline after chronic overdosage than younger patients. For these reasons, the maximum infusion rate of theophylline in patients greater than 60 years of age ordinarily should not exceed 17 mg/hr. unless the patient continues to be symptomatic and the steady state serum theophylline concentration is < 10 mcg/mL (see DOSAGE AND ADMINISTRATION). Theophylline infusion rates greater than 17 mg/hr. should be prescribed with caution in elderly patients.
Last reviewed on RxList: 2/13/2009
This monograph has been modified to include the generic and brand name in many instances.
Additional Theophylline 5% Dextrose Injection Flexible Information
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