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Drugs, Supplies and Delivery
Caffeine
Caffeine is a widely consumed central nervous system (CNS) stimulant found naturally in coffee, tea, and cocoa, and added to medications, energy drinks, and supplements. It is used medically to treat conditions like neonatal apnea and to enhance alertness or pain relief. This article provides a detailed overview of caffeine, referencing authoritative sources such as the British National Formulary (BNF), Lippincott Textbook of Pharmacology, and Lange Basic & Clinical Pharmacology. We will explore its mechanism of action, uses, dosage, side effects, precautions, drug interactions, and generic names in pharmacy.
Caffeine exerts its effects through multiple pathways:
- Adenosine Receptor Antagonism:
- Blocks adenosine A<sub>1</sub> and A<sub>2A</sub> receptors in the brain, preventing adenosine-induced sedation and vasodilation (Lippincott).
- Increases dopamine and norepinephrine release, enhancing alertness and cognitive function (Lange).
- Phosphodiesterase Inhibition:
- Inhibits phosphodiesterase enzymes, elevating cyclic AMP (cAMP) levels, though this effect is minimal in humans at typical doses (BNF).
- Calcium Mobilization:
- Enhances intracellular calcium release in muscle cells, contributing to mild bronchodilation and cardiac stimulation (Lippincott).
Caffeine is used for:
- Neonatal Apnea:
- Caffeine citrate is FDA-approved to treat apnea of prematurity by stimulating respiratory drive (BNF).
- Analgesic Adjuvant:
- Enhances the efficacy of pain relievers (e.g., paracetamol, NSAIDs) in migraine and tension headache formulations (Lange).
- Alertness and Fatigue Reduction:
- OTC tablets or beverages to combat drowsiness (e.g., shift work, driving).
- Off-Label Uses:
- Investigated for cognitive enhancement, asthma (bronchodilation), and weight loss (Lippincott).
Dosage varies by indication and formulation:
Neonatal Apnea (Caffeine Citrate):
- Loading Dose: 20 mg/kg IV or orally.
- Maintenance Dose: 5–10 mg/kg/day (BNF).
Adults (Alertness/Fatigue):
- OTC Tablets: 100–200 mg every 3–4 hours, not exceeding 400 mg/day (Lippincott).
Combination Analgesics:
- Often combined with 100–130 mg caffeine per dose (e.g., Excedrin®).
Caffeine is generally safe in moderation but may cause:
Common:
- Insomnia, restlessness, or anxiety.
- Gastrointestinal upset (nausea, acid reflux).
- Tachycardia or palpitations.
Severe (High Doses):
- Arrhythmias, hypertension, or seizures.
- Caffeine Toxicity: Symptoms include vomiting, hallucinations, and metabolic acidosis (Lange).
Before using caffeine, consider:
- Cardiovascular Conditions: Avoid in uncontrolled hypertension or arrhythmias (BNF).
- Psychiatric Disorders: May exacerbate anxiety or insomnia.
- Pregnancy: Limit to ≤200 mg/day; high doses linked to miscarriage (BNF Category: C).
- Metabolism: CYP1A2 enzyme polymorphisms affect clearance; slow metabolizers are at higher risk of toxicity (Lange).
Caffeine interacts with:
- Stimulants (e.g., amphetamines):
- Additive CNS stimulation, increasing arrhythmia risk.
- MAO Inhibitors (e.g., phenelzine):
- May cause hypertensive crises (Lippincott).
- Quinolone Antibiotics (e.g., ciprofloxacin):
- Inhibit CYP1A2, increasing caffeine levels (BNF).
- Theophylline:
- Synergistic toxicity (both are methylxanthines).
- Oral Contraceptives:
- Reduce caffeine metabolism, prolonging its effects (Lange).
Generic Names in Pharmacy
- Caffeine (active ingredient)
- Caffeine citrate (used in neonatal apnea)
- Common brand names: NoDoz®, Vivarin®, Cafcit® (IV formulation)
