Trihexyphenidyl + Chlorpromazine Pharmacology

Trihexyphenidyl + Chlorpromazine

About Trihexyphenidyl + Chlorpromazine
Mechanism of Action of Trihexyphenidyl + Chlorpromazine
Pharmacokinets of Trihexyphenidyl + Chlorpromazine
Onset of Action for Trihexyphenidyl + Chlorpromazine
Duration of Action for Trihexyphenidyl + Chlorpromazine
Half Life of Trihexyphenidyl + Chlorpromazine
Side Effects of Trihexyphenidyl + Chlorpromazine
Contra-indications of Trihexyphenidyl + Chlorpromazine
Special Precautions while taking Trihexyphenidyl + Chlorpromazine
Pregnancy Related Information
Old Age Related Information
Breast Feeding Related Information
Children Related Information
Indications for Trihexyphenidyl + Chlorpromazine
Interactions for Trihexyphenidyl + Chlorpromazine
Typical Dosage for Trihexyphenidyl + Chlorpromazine
Schedule of Trihexyphenidyl + Chlorpromazine
Storage Requirements for Trihexyphenidyl + Chlorpromazine
Effects of Missed Dosage of Trihexyphenidyl + Chlorpromazine
Effects of Overdose of Trihexyphenidyl + Chlorpromazine


About Trihexyphenidyl
Anticholinergic(antimuscarinic), Anti-Parkinson`s Agent ,synthetic antispasmodic.
Mechanism of Action of Trihexyphenidyl
Trihexyphenidyl is a synthetic Atropine substitute. It produces antiparkinsonian action by blocking the central cholinergic receptors. It inhibits cerebral cortex centers and blocks efferent impulses.
Trihexyphenidyl produces Mydriasis, increase the heart rate and spasmolytic action on smooth muscles. It decreases sweating and salivation.
Pharmacokinets of Trihexyphenidyl
Absorption: It is rapidly absorbed after oral administration.
Distribution: It crosses the blood brain barrier.
Excretion: It is excreted in urine.
Onset of Action for Trihexyphenidyl
1 hour
Duration of Action for Trihexyphenidyl
6 - 12 hours
Half Life of Trihexyphenidyl
3.7 hours
Side Effects of Trihexyphenidyl
1. Dry mouth
2. Nausea
3. Vomiting
4. Constipation
5. Abdominal cramps
6. Dizziness
7. Headache
8. Nervousness
9. Drowsiness
10. Blurred vision
11. Irritability
12. Tachycardia
13. Urinary retention
14. Mydriasis
15. Increased intraocular pressure
Contra-indications of Trihexyphenidyl
1. Hypersensitivity to Trihexyphenidyl
Special Precautions while taking Trihexyphenidyl
1. Renal impairment
2. Hepatic impairment
3. Cardiac impairment
4. Gastrointestinal obstructive disease
5. Genitourinary obstructive disease
6. Glaucoma
7. Prostatic hyperplasia
8. Slowly withdraw the drug with caution
9. Patient should be cautioned about driving a vehicle operating a machine or involving in any hazardous activities
Pregnancy Related Information
Old Age Related Information
Use with caution
Breast Feeding Related Information
Use with caution
Children Related Information
NEONATES : Contraindicated
Indications for Trihexyphenidyl
1. Parkinsonism (idiopathic and drug induced Parkinsonism)
Interactions for Trihexyphenidyl
Amantadine: Increased incidence of anticholinergic side effects which disappear on reducing the dose of trihexiphenidyl.
Digoxin: Serum levels of digoxin increased when given orally as a slow dissolution tablet.
Haloperidol: Decreased Haloperidol serum concentration may result in worsening of schizophrenic symptoms; also development of tardive dyskinesia.
Levodopa: Efficacy of levodopa may be reduced.
Typical Dosage for Trihexyphenidyl
Idiopathic Parkinsonism: initial dose: 1mg / day gradually increase the dose every 3 - 5 days up to 10 - 15 mg /day in 3 - 4 divided doses.
Post encephalitic Parkinsonism: 12 - 15 mg / day in divided doses.
Drug induced Parkinsonism: 5- 15 mg / day in divided doses
Schedule of Trihexyphenidyl
Storage Requirements for Trihexyphenidyl
Store at 15 - 30 degree C
Effects of Missed Dosage of Trihexyphenidyl
Take the missed dose as soon as noticed and if it is the time for next dose then skip the missed dose. Continue the regular schedule. Do not double the dose.
Effects of Overdose of Trihexyphenidyl
Give supportive measures and symptomatic treatment. Drug can be removed from the body by gastric lavage or inducing emesis. Absorption of the drug can be reduced by administration of activated charcoal. Control excitement with Diazepam (IV). Physostigmine is given to counteract the antimuscarinic effect of Trihexyphenidyl.


About Chlorpromazine
Aliphatic phenothiazine derivative, First-Generation Antipsychotic(typical), anticholinergic, antidopaminergic, antihistaminic, and antiadrenergic, Tranquilizer, Antiemetic
Mechanism of Action of Chlorpromazine
Antipsychotic action: Chlorpromazine binds to the dopamine receptor (D1, D2, D3 &D4).It exerts its antipsychotic activity by blocking the dopamine projections in the limbic system and in mesocortical area. Peripherally and centrally it acts as a competitive Dopamine antagonist. Chlorpromazine also produces alpha adrenergic blocking activity and anticholinergic activity. It also produces weak H1 antihistaminic activity and anti serotonin activity.
Antiemetic action: Chlorpromazine exerts its antiemetic action by blocking the dopamine receptor in the medullary chemoreceptor trigger zone.
Antimigraine action: Chlorpromazine has been used in migraine to control severe nausea and vomiting unresponsive to Antiemetics and to relieve the pain of severe migraine attacks unresponsive to parenteral Dihydroergotamine or Sumatriptan.
Anaesthetic adjuncts: It is used as anaesthetic adjunct since it allays anxiety, smoothen induction and produce antiemetic action.
Pharmacokinets of Chlorpromazine
Absorption: It is absorbed after oral administration. Absorption rate varies with route of administration. Distribution: It is distributed widely in the body in protein bound form. Metabolism: It is metabolised in the liver and produce both active and inactive metabolites. Excretion: It is excreted mainly through urine. Small amount of drug is excreted through faeces and breast milk.
Onset of Action for Chlorpromazine
30-60 minutes
Duration of Action for Chlorpromazine
4 - 6 hour
Half Life of Chlorpromazine
16 - 30 hours
Side Effects of Chlorpromazine
1.Tardive dyskinesia
2.Extrapyramidal reactions
7.Dry mouth
9.Blurred vision
13.Urine retention
14.Cholestatic jaundice
15.Aplastic anaemia
16.Pain at injection site.
Contra-indications of Chlorpromazine
1.Hypersensitivity to Chlorpromazine and other Phenothiazines
3.Bone marrow depression
Special Precautions while taking Chlorpromazine
1.Renal impairment
2.Hepatic impairment
3.Cardiovascular disease
7.Respiratory disorder
8.Prostatic hyperplasia
9.Ceribrovascular disorder
10.Patient on ECT
11.Reaction to Insulin
12.Patient exposed to extreme heat or cold or phosphorus insecticides
13.Slowly withdraw the drug with caution
Pregnancy Related Information
Old Age Related Information
Use with caution
Breast Feeding Related Information
Children Related Information
Use with caution
CHILDREN (below 6 months): Contraindicated
Indications for Chlorpromazine
2.Nausea and vomiting
3.Relief of apprehension and restlessness before surgery
4.Acute intermittent Porphyria
5.Intractable hiccups
6.Manic depressive illness
7.Behavioral problems in children
Interactions for Chlorpromazine
Alcohol: CNS depression, extrapyramidal reactions.
Aluminium salts: Decrease efficacy. Antacids should be given 1 hour before or 2 hours after chlorpromazine administration.
Anticholinergics: Decrease efficacy and increase the anticholinergic side effects of chlorpromazine.
Barbiturates: Decreases efficacy.
Barbiturate anaesthetics: Increase frequency and severity of neuromuscular excitation and hypotension.
Bromocriptine: Efficacy decreased by chlorpromazine.
Charcoal: Prevents absorption of chlorpromazine.
Epinephrine, Norepinephrine: Pressor effect decreased, peripheral vasoconstrictive effect antagonised.
Lithium: Disorientation, unconsciousness and extrapyramidal symptoms.
Meperidine: Excessive sedation and hypotension.
TCAs: Serum concentration increased by chlorpromazine.
Valproic acid: Efficacy potentiated.
Propranolol: Increased plasma levels of both drugs.
MAOIs: Additive orthostatic hypotensive effect.
Lab. Tests: Pregnancy tests: False positive results.
Plasma bound iodine (PBI): Increase in PBI occurs.
Typical Dosage for Chlorpromazine
Psychoses: 25 mg 3 times a day. Dose can be gradually increased up to 800 mg / day
Maintenance dose: 75 - 300 mg / day in 3 divided doses
Nausea and vomiting: 40 - 100 mg / day in 4 divided doses. Dose can be increased if necessary.
Relief of apprehension and restlessness before surgery: 25 - 50 mg given 2 - 3 hour before surgery. If necessary the drug can be given during surgery dose is 12.5 mg as IM injection.
Acute intermittent Porphyria, Intractable hiccups: 25 - 50 mg every 6 - 8 hourly
Migraine: 12.5 mg as IV and is repeated every 20minutes up to 37.5 mg
Behavioral problems in children: 0.55 mg/ kg/ dose 4 - 6 times a day. Dose can be increased depending on the severity of patient`s condition
Schedule of Chlorpromazine
Storage Requirements for Chlorpromazine
The drug should be kept at 15-30 degree C in a tightly closed container. Protect from heat and light. Keep out of the reach of children
Effects of Missed Dosage of Chlorpromazine
Take the missed dose as soon as noticed and if it is the time to take the next dose then skip the missed dose.
Effects of Overdose of Chlorpromazine
Give supportive measures and symptomatic treatment.

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