The mechanism of action of anticholinergics is believed be involved in correcting the disequilibrium between striatal dopamine and acetylcholine neurotransmission. Some anticholinergics, e.g. benzotropine, can also block dopamine uptake in central dopaminergic neurons. The anticholinergics used to treat PD specifically block muscarinic receptors. These drugs have only a small effect on PD symptoms, and that evidence for a special effect on tremor is inconclusive. Because of the risk of side effects, centrally acting anticholinergics are usually not advised for the therapy of non - motor, i.e. autonomic, dysfunctions.
The clinical use of anticholinergics has been limited by their side- effect profiles and contraindications. The most commonly reported side effects are blurred vision,urinary retention, nausea, constipation (rarely leading to paralytic ileus), and dry mouth. The incidence of reduced sweating, particularly in those patients on neuroleptics, can lead to fatal heat stroke.
Anticholinergics are contraindicated in patients with narrow-angle glaucoma, tachycardia, hypertrophy of the prostate, gastrointestinal obstruction, and megacolon. Impaired mental function (mainly immediate memory and memory acquisition) and acute confusional state are a well documented central side effect that resolves after drug withdrawal. Therefore, if dementia is present, the use of anticholinergics is contraindicated. The abrupt withdrawal of anticholinergics may lead to a rebound effect with marked deterioration of parkinsonism. Consequently, anticholinergics should be discontinued gradually and with caution.
An anticholinergic preparation which is commercially available in the Philippines is biperiden HCl. The brand names are (AKINETON) by ABBOTT, (AKIDIN) by MED CHOICE PHARMA and (AKETON) by YOO YOUNG. The indications, dosage, manner of administration, contraindications, special precautions, adverse reactions and drug interactions are as follows:
INDICATIONS:
TAB: Adjunct therapy of all forms of parkinsonism (post-encephalitic, arteriosclerotic and idiopathic)
AMP: Symptomatic treatment of parkinsonism including the alleviation of the extrapyramidal syndrome induced by drugs
DOSAGE:
TAB: Adult Parkinsonism : Initially 1 mg BID, increased by 2 mg/day. Maximum: 16 mg daily
Drug-induced movement disorders : 1-4 mg once-QID
Children : 3-15 yr 1-2 mg once-TID
ADMINISTRATION: May be taken with or without food
CONTRAINDICATIONS:
Untreated narrow-angle glaucoma
Intestinal stenoses or obstruction
Megacolon
Prostatic hypertrophy
Life-threatening tachycardia
SPECIAL PRECAUTIONS:
Avoid abrupt discontinuation.
Increased sensitivity to side effects especially elderly.
Enhanced risk of cerebral seizures in predisposed persons.
Abuse
Impaired ability to drive or operate machinery.
ADVERSE REACTIONS:
Fatigue
Dizziness
Drowsiness
Dry mouth
Rarely : Swelling of salivary glands
Accommodation difficulties
Mydriasis
Photophobia
Hypohydrosis
Constipation
Gastric symptoms
Nausea
Tachycardia
Very rarely: Bradycardia, especially at higher doses
Restlessness
Agitation
Anxiety
Confusion
Euphoria
Occasionally: Impairment of memory
In rare cases: Delirium
Hallucinations
Nervousness
Headache
Insomnia
Dyskinesia
Ataxia
Muscle twitching
Speech Impairment
DRUG INTERACTIONS:
Enhanced anticholinergic effects in combination with other psychotropic drugs
Antihistamines
Antiparkinsonism drugs
Antispasmodics
Quinidine
Pethidine
Dyskinesia induced by levodopa may be potentiated
Effects of alcohol may be enhanced
Antagonistic influence on the action of metoclopramide and compound of similar activity in the GIT.
To get an update in the diagnosis and management of Parkinson's disease, Pinoy Parkinson's Disease or Pinoy PD is holding its First Annual Convention on October 22, 2011 in Makati City.
P.S. EXTENDED FREE REGISTRATION! Register for FREE on or before OCTOBER 15, 2011.
P.P.S. Register for a GUARANTEED SEAT and SLOT in the workshop to a LIMITED NUMBER of participants on or before OCTOBER 15, 2011 including LUNCH, 2 SNACKS and SEMINAR KIT.
P.P.P.S. Submit REGISTRATION DETAILS (Name, Age, Contact number and E-mail address) on or before OCTOBER 15, 2011 to avail of FREE REGISTRATION and send via email to drajoy31@yahoo.com / drajoy31@gmail.com
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