Adult: As tab: Usual dose: 50-100 mg, or up to 200 mg. Doses must not be taken more often than 3 or 4 hourly. Dosage recommendations may vary among countries and individual products (refer to detailed product guideline). Child: As tab: Dosage recommendations may vary among countries and individual products (refer to detailed product guideline).
Administration
May be taken with or without food.
Contraindications
Symptomatic or history of cardiac arrhythmia, anxiety disorders. Concomitant use with other xanthines (e.g. theophylline).
Special Precautions
Patient with existing or history of seizure disorders, other known CV diseases, history of peptic ulcer and/or GERD, hypertension, agitation, tremor. Patient recovering from chronic alcoholism and is taking disulfiram. Caffeine-naive and -sensitive individual. Renal and hepatic impairment. Neonates and children. Pregnancy and lactation.
When used for apnoea of prematurity: Rule out or properly treat other causes of apnoea (e.g. CNS disorders, primary lung disease, anaemia, sepsis, metabolic disturbances, CV abnormalities, obstructive apnoea) before initiating treatment; monitor caffeine plasma concentrations periodically during treatment (in case of incomplete clinical response or signs of toxicity); heart rate, number and severity of apnoea spells (as necessary); serum glucose periodically (in infants receiving caffeine citrate). Obtain baseline caffeine plasma concentrations before initiating treatment in neonates born to mothers who consumed large quantities of caffeine before delivery, or in neonates previously treated with theophylline. Monitor for development of necrotising enterocolitis.
Overdosage
Symptoms: Seizure, jitteriness, tachypnoea, tachycardia, opisthotonos, rigidity, tonic-clonic movements, hypokalaemia, fine tremor of extremities, gastric irritation, restlessness, gastrointestinal haemorrhage, involuntary jaw and lip movements, increased WBC count, compromised circulation, vomiting, fever, agitation, hypertonia, gastric residues, hyperexcitability, distended abdomen, metabolic acidosis, hyperglycaemia, increased urea levels, pallor, dilated pupils, insomnia, headache, rapid speech, diuresis, tinnitus, and elevated respiration. Management: Supportive and symptomatic treatment. Monitor blood levels of caffeine and electrolyte (e.g. plasma K). Correct hypokalaemia and hyperglycaemia. Consider exchange transfusion for severe cases. Administer IV anticonvulsants (e.g. diazepam, phenobarbital) to treat convulsion. May administer activated charcoal (adult: 50 g; children: 10-15 g) or perform gastric lavage (in adults) within 1 hour of ingestion; correct electrolyte imbalances if needed. Monitor pulse, cardiac rhythm, and blood pressure. Administer amiodarone or disopyramide for ventricular arrhythmias occurring in patients having convulsions. May give β-blocker for persistent hypertension.
Drug Interactions
Decreased elimination or clearance with cimetidine, ketoconazole, pipemidic acid or methoxsalen. Increased elimination or clearance with phenobarbital, phenytoin or disulfiram. May decrease the vasodilating effect of adenosine and dipyridamole. May enhance the tachycardic effect of phenylpropanolamine. May antagonise the effect of tranquilisers, sedatives and β-blockers (e.g. atenolol, metoprolol, propranolol). Inhibits the metabolism of clozapine. Significant CV effects with ephedrine. Concomitant use with lithium carbonate may result in small to moderate increase in serum lithium levels. May increase stimulant effects with MAOIs. Potentially Fatal: Interconversion between caffeine and other xanthines (e.g. theophylline) may occur in preterm neonates.
Food Interaction
May increase caffeine levels when given concomitantly with other caffeine-containing foods or beverages which may cause nervousness, irritability, sleeplessness or rapid heartbeat.
Action
Description: Mechanism of Action: Caffeine is a methylxanthine that inhibits the phosphodiesterase enzyme and has antagonistic activity on central adenosine receptors. It is a CNS stimulant, especially in the higher centres, and can result in a wakefulness condition and enhanced mental activity. Although its exact mechanism in apnoea of prematurity is unknown, it is believed to have several effects including stimulation of the respiratory centre, reducing threshold to hypercapnia and diaphragmatic fatigue; increasing minute ventilation, skeletal muscle tone, metabolic rate and oxygen consumption. Pharmacokinetics: Absorption: Rapidly and completely absorbed from the gastrointestinal tract. Time to peak plasma concentration: 30 minutes to 2 hours (neonates). Distribution: Widely distributed throughout the body; readily passes into the CNS and saliva (caffeine citrate). Crosses the placenta; enters breast milk (small amounts). Volume of distribution: 0.8-0.9 L/kg (neonates); 0.6 L/kg (adults). Plasma protein binding: Approx 36%. Metabolism: Almost completely metabolised in the liver via oxidation, demethylation, and acetylation by CYP1A2. Excretion: Via urine (adults: approx 1% as unchanged drug; neonates: 86% as unchanged drug). Elimination half-life: Approx 3-7 hours (adults); approx 3-4 days (neonates).
Chemical Structure
Caffeine Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 2519, Caffeine. https://pubchem.ncbi.nlm.nih.gov/compound/Caffeine. Accessed Mar. 29, 2023.
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