Aminophylline

CLINICAL USE

  • Reversible airways obstruction
  • Acute severe asthma

    DOSE IN NORMAL RENAL FUNCTION

    Modified release: 225–450 mg twice daily
    IV loading dose: 5 mg/kg (250–500 mg)
    Maintenance dose: 0.5 mg/kg/hour adjusted
    according to levels

    PHARMACOKINETICS

  • Molecular weight                           :
    420.4
  • %Protein binding                           :
    40–60 (theophylline)
  • %Excreted unchanged in urine     :
  • <10           :
  • Volume of distribution (L/kg)       :
    0.4–0.7 (theophylline)
  • half-life – normal/ESRD (hrs)      :
    4–12/Unchanged
    (theophylline)

    DOSE IN RENAL IMPAIRMENT

    GFR (mL/MIN)

  • 20 to 50     : Oral: Dose as in normal renal
    function and adjust in accordance
    with blood levels
    IV: Dose as in normal renal function
    and adjust in accordance with blood
    levels
  • 10 to 20     : Oral: Dose as in normal renal
    function and adjust in accordance
    with blood levels
    IV: Dose as in normal renal function
    and adjust in accordance with blood
    levels
  • <10           :
    Oral: Dose as in normal renal
    function and adjust in accordance
    with blood levels
    IV: Dose as in normal renal function
    and adjust in accordance with blood
    levels

    DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES

  • CAPD                :
    Not dialysed. Dose as in
    GFR <10 mL/min Monitor blood
    levels. See ‘Other Information’
  • HD                     :
    Not dialysed. Dose as in
    GFR <10 mL/min. Monitor blood
    levels. See ‘Other Information’
  • HDF/high flux   :
    Unknown dialysability. Dose as in
    GFR <10 mL/min Monitor blood
    levels. See ‘Other Information’
  • CAV/VVHD      :
    Not dialysed. Dose as in GFR=10–
    20 mL/min Monitor blood levels.
    See ‘Other Information’

    IMPORTANT DRUG INTERACTIONS

    Potentially hazardous interactions with other drugs

  • Antibacterials: increased concentrationwith azithromycin, clarithromycin,
    erythromycin, ciprofloxacin, norfloxacin
    and isoniazid; decreased erythromycin
    levels if erythromycin is given orally;
    increased risk of convulsions if given
    with quinolones; rifampicin accelerates
    metabolism of theophylline
  • Antidepressants: concentration increasedby fluvoxamine – avoid concomitant use
    or halve theophylline dose and monitor
    levels; concentration reduced by St John’s
    wort – avoid concomitant use
  • Anti-epileptics: metabolism increasedby carbamazepine and primidone;
    concentration of both drugs increased
    with phenytoin
  • Antifungals: concentration increased byfluconazole and ketoconazole
  • Antivirals: metabolism of theophyllineincreased by ritonavir
  • Calcium-channel blockers: concentrationincreased by diltiazem and verapamil and
    possibly other calcium-channel blockers
  • Tacrolimus: may increase tacrolimus levels
  • Ulcer-healing drugs: metabolism inhibitedby cimetidine; absorption possibly reduced
    by sucralfate

    ADMINISTRATION

    Reconstition

    –

    Route

    IV, oral

    Rate of Administration

    Loading dose over 20 minutes by slow IV

    injection

    Comments

  • Can be added to glucose 5%, sodiumchloride 0.9% and compound sodium
    lactate
  • Minimum volumes range from 2–25 mg/mL, give concentrated solution via central
    line.

    OTHER INFORMATION

  • Aminophylline: 80% theophylline + 20%ethylenediamine
  • In bodily fluids, aminophylline rapidlydissociates from ethylenediamine and
    releases free theophylline in the body.
    It is therefore not present in the body
    long enough to be dialysed, whereas
    theophylline is dialysed, see theophylline
    monograph
  • Optimum response obtained at plasmatheophylline levels of 10 to 20 mg/L (55–110
    micromol/L)
  • Increased incidence of GI and neurologicalside effects in renal impairment at plasma
    levels above optimum range
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