Theophylline Flashcards

1
Q

Therapeutic Index

A

10-20mg/L

NARROW

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2
Q

Plasma protein binding

A

40%

LOW

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3
Q

Describe the metabolism

A

90% metabolised in liver via CYP450

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4
Q

Describe elimination

A

90% metabolised
10% via kidney unchanged (urine)
FIRST ORDER KINETICS
VARIABLE rates

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5
Q

What factors affect clearance?

A

age, illness, thyroid function, smoking, diet, drugs

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6
Q

INTERACTIONS

A

SSRIs, quinolone antibiotics, allopurinol, erythromycin, cimetidine

SMOKING

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7
Q

Which BTS step introduces theophylline - in which form?

A

STEP 3: SR theophillyne

STEP 4 as an add-on

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8
Q

Theophylline structure

A

PURINE derivative

similar to caffeine

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9
Q

Indications

A

chronic asthma
severe asthma
COPD

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10
Q

Define SUSTAINED RELEASE TABS

A

modified tabs to release drug at a predetermined rate -> achieve constant drug serum conc

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11
Q

Advantages of SR tabs

A
Avoid toxicity
Prolonged half life & efficacy
Control of drug plasma levels
ONE DAILY DOSE - enhances patient compliance
Relieve morning symptoms of asthma
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12
Q

Compare distribution or oral & IV theophylline

A

ORAL: follows one compartment model (simple)
IV: follows PK of a 2 compartment model

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13
Q

Effects of theophylline

A

reduces inflammation

enhances effects of B2-agonists & corticosteroids

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14
Q

Mechanism

A

AFFECTS MANY PATHWAYS & MEDIATORS

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15
Q

Side effects

A

NON-SPECIFIC

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16
Q

Discuss interactions with SMOKING

A

Shortens half life

CYP1A2 induction from smoke chemicals:&raquo_space; metabolism & clearance