Pharma sheet # 29 - Haitham Al-noti

بسم الله الرحمن الرحيم


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http://www.mediafire.com/?14vwij5o0p4wv3v
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In the name of god


before going in the lec. Material ( just to let you know) , the doc. Just read the slides and add few information . so I insert the slides' material as it is and add these additions.
In the previous lecture, we start to speak about the anti-epileptic agents; Basis of their Pharmacological Rx , their Categories …etc. . anyway we covered the material about the Hydantoins ( like Phenytoin ) , Benzodiazepines…..
In this lecture we complete the speech about the remaining Categories , and they are :

* Barbiturates – Phenobarbital

• Used for tonic-clonic seziures.

• Act by increasing the duration of Cl- ion channel opening by activating neuronal GABAa receptors

• Causing hyperpolarisation of the AP, making it less likely to fire again

• Essentially, acts like GABA and can even potentiate the effects of GABA when present.

Adverse effects:

– CNS effects (sedation and fatigue)
– Restlessness/Hyperactivity
– Folate deficiency
– Tolerance
– Dependence with physical withdrawal reactions
– Adverse drug-drug reactions (contraception and warfarin).

• Contraindications: Do not use with patients with respiratory depression, children or elderly.

• NOTE: low therapeutic index means more toxic and overdose can have serious consequences


* Succinimides ( Ethosuximide )

• Use for pts with Absence seizures ( patient go in ( some what very rapid coma for several minutes ) during speaking with him.

• Acts by antagonising Ca++ channels in the thalamocortical relay neurons => prevention of synchronised neuronal firing => raising AP threshold

• Adverse effects:
– Nausea, vomiting and anorexia
– Cerebellar disturbance (drowsiness, dizziness, photophobia, headache, depression)
– Skin irritation
– Not to be used when pregnant (teratogencity)


* Sodium Valproate

• Use in all forms of epilepsy, as it suppresses the initial seizure discharge and its spread.

• Clinical actions are:
– Antagonism of Na+ and Ca++ channels
– Potentiation of GABA
– Attenuation of Glutamate

• Can be fast acting due to Na+ MoA, although the full Rx effect usually takes weeks.

• Adverse effects:

– GI upset (Nausea, vomiting, anorexia, abdominal pain and diarrhoea)
– Weight gain (appetite stimulation)
– Transient hair loss
– Tremor
– Coma (rare)
– Thrombocyptopenia (platelets)
– Oedema
– Severe hepatotoxicity (liver damage)

• Contraindications: People with liver damage or a history hepatic dysfunction.


Here , we need to consider the following :

• Aspirin may result in valproic acid Toxicity; Combination should be avoided if possible.

• When administered in combination, valproic acid has been shown to reduce the metabolism of phenobarbital, changing its half-life from 96 to 142 hours.

• A delay in the elimination of phenobarbital would result in enhancement and prolongation of sedative effects.

• Oral benzodiazepines that provide effective sedation and anxiolysis are an appropriate alternative.


• Gabapentin (Neuronitin)

• Used for partial seizures in adults
• Designed to be a structural analogue of GABA but it does not mimic GABA in the brain.
• Acts via:
– Increased synthesis and release of GABA
– Decrease degradation of GABA
– Inhibition of Ca++ channels

– Effects on Dental Treatment
Key adverse event(s) related to dental treatment: Xerostomia (normal salivary flow resumes upon discontinuation), dry throat, and dental abnormalities.

# here go to the table In the last slide in the doc. Slides and note the following :

- xerostomia : dry mouth
Stomatitis : oral mucosa inflammation
Gingivitis : gingival inflammation
Glossitis : tongue inflammation
Dysgeusia : taste disturbances
Orofacial oedema : oedema in face

- in the previous drugs we care about their side effects in the table + their effect on the platelets (Thrombocyptopenia ).

- in general we use older anti epileptic drugs ( mainly ) ,and the newer drugs are used as adjuvant agent ( bet they may be used like the older drugs also) .

- we need to know the mechanism of action for Sodium Valproate
( mainly coz it is the most important drug) .

- all drugs except valproic acid may cause dental related side effect , but it is weak in comparison with that of Sodium Valproate.

- phenobarbital is rarely used as sedative agent , and the valproic acid somewhat increases its sedative effect .


- Gabapentin is used for back pains ( like disk collapse . it is widely used for neuronal pain but not as AEDs . it may be used instead of Carbamazepine )

- Barbiturates has narrow therapeutic index , but it they are cheap and easier to deal with .

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* Parkinson’s Disease ( neuronal degeneration)

• A degenerative and progressive disorder

• Associated with neurological consequences of decreased dopamine levels produced by the basal ganglia (substantia nigra)

• Dopamine is a neurotransmitter found in the neural synapses in the brain

• Balance, posture, muscle tone and involuntary movement depends on the roles of dopamine (inhibitory) and acetylcholine (Ach: excitatory)


• If dopamine missing, Ach produces more of an effect on muscles

• Pharmacological basis of anti-parkinson drugs:
– Restore dopamine function
– Inhibit Ach within corpus striatum

Medication Rational ( possible solutions)

• Replace depleted levels of dopamine

• Stimulate the nerve receptors enabling neurotransmission

• Increase the effect of dopamine on nerve receptors (agonist)

• Counteract the imbalance of Ach and Dopamine




The Drugs:


– Dopaminergic drugs (improving dopamine functioning)

• Levodopa
• Dopamine receptor agonists
• Amantadine
• Selective monoamine oxidase B inhibitors
• Catechol-O-methyltransferase inhibitors

– Antimuscarinic drugs (Ach inhibitors)

* Levodopa (Madopar & Sinemet)

• Can not administer dopamine directly, as it does not cross the blood brain barrier

• A natural amino acid that the brain converts into dopamine (replacement therapy) used since the 1960’s.

• Levodopa is combined with Carbidopa, which is a dopamine decarboxylase inhibitor that does not cross the blood brain barriers ( the main target from this drug is to build up the required amount of dopamine come from levodopa after passing the blood brain barrier by the effect of the dopamine decarboxylase which present everywhere in the body but can't cross the blood brain barrier . so we use carbidopa to inhibit the effect of this enzyme in all body site (except in the CNS) ,so prevent the conversion to dopamine to : - protect the body from the dopamine accumulation side effect ( dangerous)
- keep the amount of drug available to pass the blood brain barrier and give the required amount of dopamine in CNS)

# here go to the slides and follow the way by which this drug does it's action.( if you want)



• Adverse effects:

– As a result of the amount of peripheral dopamine levels
• Nausea, vomiting
• Postural hypotension

– As a result of the amount of CNS dopamine levels
• Dyskinetic involuntary movements (face & neck)
• Hallucinations and confusion

# Dental consideration

• Parkinsonian tremors of the orofacial musculature and the use of levodopa-containing medications may cause bruxism;

• therefore, the dentist should examine the dentition of a patient with PD for excessive loss of tooth structure.


Notes:

- to decrease the Ach amount( which is normal) as a treatment for Parkinson isn't a good solution because the problem initially is in dopamine .

- we note( in patient with Parkinson disease ) difficulty in swallowing and mouth( and other movement ) movement.

- In Parkinson disease , we ( as dentists ) deals with elderly patient . this isn't true in epilepsy which present in patient from childhood ( we deal with young patient mainly)

- All side effects result from dopamine ( the best vasopresser , affect peripheral movement ) are important in dentistry so try to study them well.