162 Section 3/ Drugs Acting on ANSIn higher doses, atropine produces dilatation
of the cutaneous blood vessels which may
be due to paralysis of vasomotor centre.
Effect on central nervous system: In
therapeutic doses, atropine causes stimula-
tion of medullary vagal nuclei and higher
cerebral centres and may produce bradycar-
dia and increase in rate & depth of respira-
tion. By depressing vestibular excitation, it
has antimotion sickness property. It also de-
creases tremors and rigidity in parkinsonism
by blocking relative cholinergic overactivity
in basal ganglia. Scopolamine also stimulates
the respiratory and vagal centres. Toxic doses
of atropine may lead to CNS excitatory ef-
fects e.g. restlessness, anxiety, insomnia, de-
lusions and hallucinations etc. It also cause
medullary paralysis (respiratory paralysis) in
still higher dose.
Both atropine and scopolamine induce
sleep like pattern of EEG, it also cause rise in
body temperature due to its action onTable 3.5.1: Classification of anticholinergic agents.
I. Natural alkaloids
Atropine (used as sulphate; ATRO) 0.5-2 mg IM/IV, 1-2% topical (eye)
Hyoscine (Scopolamine; BELLADENAL) 0.3-0.5 mg oral/IM
II. Semisynthetic compounds
Homatropine (HOMARIN FORTE) 1-3% topical (eye)
Atropine methonitrate (SPASMOLYSIN) 2.5-10 mg oral/IM
as inhalant (BROVON INHALANT) 0.1-0.2% inhalation
Hyoscine methylbromide 2.5 mg oral/IM
Ipratropium bromide (IPRAVENT) 40-80 μg inhalation
III. Synthetic compounds
i. Used as mydriatics
Cyclopentolate (CYCLATE) 0.5-2% topical (eye)
Tropicamide (ITROP PLUS) 0.5-1% topical (eye)
ii. Used as antisecretory-antispasmodics
Glycopyrrolate (GLYCO) 1-2 mg oral, 0.1-0.3 mg IM
Pipenzolate methylbromide (PIPTAL) 5-10 mg/day
Isopropamide (STELABID) 5 mg/day
Mepenzolate methylbromide 30-60 mg/day
Dicyclomine (CATASPA) 10-20 mg/day TDS
Pirenzepine 100-150 mg/day
Flavoxate (URIPAS) 100-200 mg/day TDS-QID
Mebeverine (COLOSPA) 135 mg TDS-QID before meals
Drotaverine (DOVERIN) 40-80 mg TDS
Valethamate (VALOSIN) 10-20 mg BD-TDS
iii. Used as antiparkinsonian agents
Trihexyphenidyl (PACITANE) 2 mg OD-QID
Procyclidine (KEMADRIN) 2.5-5 mg TDS
Biperiden (DYSKINON) 2-10 mg oral/IM/IV
Benztropine (COGENTIN) 1-2 mg oral/IM OD-TDS
Cycrimine (PAGITANE) 2.5-5 mg OD-TDS