Name of the Methylxanthines Drugs
- Theophylline
- Aminophylline
- Choline theophyllinate
- Hydroxyethyl theophyllinate
- Doxophylline
Mechanism of Action
Through non-competitive inhibition of the phosphodiesterase enzyme (PDE), methylxanthines cause an intracellular increase in levels of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP)
1.THEOPHYLLINE
| Theophylline |
| Availability : Capsules (immediate-release): 100 mg, 200 mg ,Injection (with dextrose): 0.4 mg/ml, 0.8 mg/ml, 1.6 mg/ml, 2 mg/ml, 3.2 mg/ ml, 4 mg/ml ,Syrup (cherry): 80 mg/15 mg, 150 mg/ 15 ml ,Tablets (immediate-release): 100 mg, 125 mg, 200 mg, 250 mg, 300 mg |
| Administration and handling: Adults (otherwise healthy nonsmokers): Initially, 6 mg/kg P.O., followed in next 12 to 16 hours by 3 mg/kg P.O. q 6 hours for two doses, then a maintenance dosage of 3 mg/kg P.O. q 8 hours ●Children ages 9 to 16; young adult smokers: Initially, 6 mg/kg P.O., followed in next 12 to 16 hours by 3 mg/ kg P.O. q 4 hours for three doses, then a maintenance dosage of 3 mg/kg P.O. q 6 hours ●Children ages 1 to 9: Initially, 6 mg/kg P.O., followed in next 12 to 16 hours by 4 mg/kg P.O. q 4 hours for three doses, 4 mg/kg P.O. q 6 hours |
| Mechanism of Action: Relaxes bronchial smooth muscles, suppressing airway response to stimuli. Also inhibits phosphodiesterase and release of slow-reacting substance of anaphylaxis and histamine. |
| Contraindications :Hypersensitivity to theophylline or its components, peptic ulcer disease, uncontrolled seizure disorder |
| Precautions: Use cautiously in: ● alcoholism; heart failure or other cardiac or circulatory impairment; hypertension; renal or hepatic disease’s; hypoxemia; hyperthyroidism; diabetes mellitus; glaucoma; peptic ulcer disease ● elderly patients ● children younger than age 1. |
| Indications: Acute bronchospasm in patients not receiving theophylline |
Nursing Considerations
- Be aware that ideal body weight is used to calculate theophylline dosages because drug doesn’t bind well in body fat.
- Be aware that E.R. capsules and tablets shouldn’t be used for oral loading doses.
- Infuse theophylline loading dose, bolus, or intermittent infusion at a rate that doesn’t exceed 25 mg/min.
- Administer continuous theophylline infusion with rate-controlled infusion device.
- Monitor blood theophylline level, as ordered, to gauge therapeutic level and detect toxicity.
- Frequently assess heart rate and rhythm because theophylline can exacerbate existing arrhythmias.
- Be especially alert for signs of toxicity in patient with acute pulmonary edema, hypothyroidism, influenza vaccination, prolonged fever, sepsis with multiple organ failure, shock, or viral pulmonary infection because of decreased drug clearance.
- Monitor blood theophylline level in patients with uncorrected acidemia because they have an increased risk of toxicity
2.AMINOPHYLLINE
| Aminophylline |
| Availability :Oral dose ranges from 400 to 600 mg/day.Intravenous 10 to 15 mcg/ml. |
| Administration and handling: Adults and children not currently receiving theophylline products. Initial: 6 mg/kg |
| Mechanism of Action: Inhibits phosphodiesterase enzymes, causing bronchodilation. Normally, these enzymes inactivate cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), which are responsible for bronchial smooth-muscle relaxation. Other mechanisms of action may include translocation of calcium, prostaglandin antagonism, stimulation of catecholamines, inhibition of cGMP metabolism, and adenosine receptor antagonism. |
| Contraindications :Active peptic ulcer disease, hypersensitivity to aminophylline, rectal or lower intestine irritation or infection (suppository form), underlying seizure disorder |
| Precautions: ● COPD, diabetes mellitus, glaucoma, renal or hepatic disease, heart failure or other cardiac or circulatory impairment, hypertension, hyperthyroidism, peptic ulcer, severe hypoxemia ● active peptic ulcer disease ● elderly patients ● neonates, infants, and young children |
| Indications: •Prevention of apnea in preterm infants •Thigh cellulite creams •Sleep apnea |
Nursing Considerations
- To determine peak serum theophylline level, draw blood sample 15 to 30 minutes after administering I.V. loading dose. • Give immediate-release and liquid forms with food to reduce GI upset.
- Give E.R. form 1 hour before or 2 hours after meals because food can alter drug absorption.
PATIENT TEACHING
- Advise patient to avoid excessive caffeine (in coffee, tea, soft drinks, and chocolate); it can falsely elevate theophylline level.
- Explain that blood tests may be needed to monitor drug’s therapeutic effect.
3.DOXOPHYLLINE
| Doxophylline |
| Availability : Oral Adult 0.2-0.4g daily Child 10-14 years 400-800mg , 5-9 yrs 200-400 mg <5 yrs 24-36 mg/kg body weight |
| Administration and handling: Adult 0.2-0.4g daily Child 10-14 years 400-800mg , 5-9 yrs 200-400 mg <5 yrs 24-36 mg/kg body weight |
| Mechanism of Action:choline theophyllinate is a theophyilline which ilberates theophylline in the body.It inhilbilt the activity of phosphodiesterase , resulting in the intracellular accumulation of cyclic adenosine monophosphate thus leading to bronchodilation |
| Contraindications : Peptic ulcer , Gastritis ,Hypersensitivity to the drug |
| Precautions: Peptic ulceration, hyperthyroidism, hypertension, cardiac arrhythmias, or other cv disease epilepsy, hepatic dysfunction, chronic alcoholism, acute febrile illness, smoking |
| Indications: Oxtriphylline (Choline Theophyllinate) is primarily indicated in conditions like Asthma, Bronchitis, Bronchospasm, emphysema |
4.Hydroxyethyl theophyllinate
| Hydroxyethyl theophyllinate |
| Availability : oral 400 mg ,200 mg |
| Administration and handling: adult 400 mg bid –tid max.1200 mg daily Elderly 200 mg bid-tid Child :< 12years 6-9 mg/kg bid >- 12 years 200 mg bid-tid |
| Mechanism of Action:7-(β-Hydroxyethyl) theophylline is a methylxanthine phosphodiesterase (PDE) inhibitor. It reduces histamine, 5-hydroxytryptamine, and bradykinin-induced bronchoconstriction in an anesthetized guinea pig model of bronchial asthma. |
| Contraindications : Acute MI , hypotension , lactation |
| Precautions : patient with cv disease , COPD , active history of peptic ulcer , hypothyroidism , hypoxaemia ,concomitant infection history of seizure disorders |
| Indications: Headache, Nausea, Vomiting, Stomach pain, Irritability, Insomnia (difficulty in falling or staying asleep), Fast heart rate |
REFERENCES
- Robert Kizior, Keith Hodgson, Saunders Nursing Drug handbook,1st edition 2024, Elsevier Publications. ISBN-9780443116070
- McGraw Hill- Drug Handbook, Seventh Edition, 2013, McGraw Hill Education Publications,9780071799430.
- April Hazard, Cynthia Sanoski, Davi’s Drug Guide for Nurses -Sixteenth Edition 2019, FA Davis Company Publications,9780803669451.
- Jones and Bartlet, Pharmacology for Nurses, Second Edition, 2020, Jones and Bartlet Learning Publications, ISBN 9781284141986.
- Nursebro.com, Search – Nursebro
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