S15C186 - Methylxanthines and Nicotine OD

Question 1

Examples of Methylxanthines (4)

Answer 1

• theophylline (for bronchospastic dz)
• theobromine (found in chocolate)
• caffeine
• nicotine

Question 2

Methylxanthine Pharmacology

Answer 2

-michaelis-mentin kinetics: changes from 1st order to zero-order kinetics at increased concns, so that a fixed amount (not %age) of drug is eliminated per unit of time

Question 3

Methylxanthine: mechanism of toxicity

Answer 3

• adenosine antagonism: increases excitatory neurotransmitter activity, causes bronchodilation but also vasoconstriction, arrhythmias, seizures
• increased catecholamines: (epi, NE), stimulation of beta 1 and 2 R’s, bronchodilations, but also tachycardia, vasodilation, HoTN
• inhibits phosphodiesterase: increased cAMP and catecholamines, causes increased beta-adrenergic effects

Question 4

Methylxanthine toxicity: clinical Sx

Answer 4

• GI: n/v
• Neuro: tremor, agitation, Sz
• CVS: HoTN, tachy, arrhythmias
• Metabolic: hypokalemia, metabolic acidosis, hyperglycemia, hyperthermia, rhabdo

Question 5

Methylxanthine w/d:

Answer 5

• starts 6-24h after last dose, peaks at 36h, lasts days

- h/a, fatigue

Question 6

Methylxanthine OD Tx

Answer 6

• ABC
• D: activated charcoal
• tx of Sz: benzos, barbiturates
• phenytoin contraindicated
• tx of arrhythmias: consult tox, consider BB
• E: HD if acute level >90mcg/ml or chronic >40mcg/ml with symptoms

Question 7

Contraindications to Activated Charcoal

Answer 7

• unprotected airway
• n/v
• ileus
• bowel obstruction
• need for emergent endoscopy

Question 8

Nicotine OD

Answer 8

• GI: n/v
• Ach activation: tremor, dizziness, tachy, bronchorrhea
• large doses cause Ach inactivation: bradycardia, arrhythmias, hypoventilaion, coma, Sz
• tx Sz with benzo

-if asymptomatic, after 3h of acute ingestion pt can be d/c