pharmacology: Spasmolytic drug

Spasmolytic drug: 

These drugs reduce abnormally elevated muscle tone that's spasm; without paralysis; without complete muscle paralysis relaxation, without loss strength of muscle

Spasmolytic agent don't ressemble Ach in the structure while both are competitive blocker.

All spasmolytic drugs are used orally; because these are highly potent compounds and unabsorbable when they are taken orally.

Spasmolytic don't act on neuromuscalar junction itself; but they are acting either:

• centrally on CNS 
• directly on muscle fiber

Drug acting on CNS centrally and spinal cord:

Diazepam:

• still used as sedative or hypnotic and some times as anticonvulsive effect
• its main effect is facilitated GABA amino gluetric acid mediated transmition 

Tizandine:

• act on spinal cord mainly
• clonidin like in their structure; used as anihypertensive 
• said to be an alpha 2 agonist

Drug acting on the muscle fiber:

Dantolene:

• act directly on the muscle fibe
• preventing Ca release from these muscle fiber; reducing the contraction or muscle tone.

pharmacology: Neuromuscular blockers

Neuromuscular blockers:

Drugs which can cause complete muscular paralysis or relaxation. there are 2 groups:

1. Competitive: characterized by long duration effects 
2. depolarizing neuromuscular: have short duration of effect.

 note: therapeutic use of these group of drug depends on the duraction of surgical procedure which we need muscular relaxation to perform. so for long duration like intraabdominal operation we will use competitive type; while for short procedure like Endotracheal intubation or electronconvulsive therapy we will use the depolarizing one (e.g., succinylicholine or suxamethonium)

note: depolarizing neuromuscular blocking agents usually given by IV infusion; because of their short duration effect.

note: after given of succinylcholine; at the beginning there will be muscular contraction; then after exhaustion of the muscle there will be relaxation.

adverse effects:

• bradycardia
• increase intraocular pressure 
• prolonged paralysis 
• malignant hyperthermia

bradycardia:
succinylcholine has muscurinic agonist activity similar to acetycholine; meaning that it can produce arrhythmia; and this might due to increase in plasma potassium level (hyperkalemia); that's why succinylcholine should be avoided in patient with severe muscular damage or tramua; becasue in these condition the plasma (blood) potassium is elevated.

Increase intraocular pressure:
succinylcholine may lead to increase introcular pressure; so its better not to use it in operation of eyeball; because it will lread to extravasation of intraocular fluid due increase in pressure

Prolonged paralysis:
these cases has been reported after treatment with succinlycholine; but only in patient with specific cases:

• patients who are genetically predisposed to have choline esterase deficiency (hypocholine esterasemia); so if there is a decrease in this enzyme (meaning choline esterase); the succinylcholine will stay for longed period in plasma or tissue; giving along duration of effect; prolonged paralysis 
• patients who receives anticholine esterase drugs 
• neonates and patients with their live disease; might have prolonged apnea; because in these group of patient there is inefficient metabolism of succinylecholine. 

Malignant hyperthermia: 
when used in patient who are receiving halogenated hydrocarbon for their general anethesia; some of theme may develop malignant hyperthermia

Chemotherapy

Chemotherapy:
its a term used for the drug treatment of parasitic infections (bacteria, portozoa, viruses, fungi, and helminthes); in which these parasites are destroyed by the drug, but without injury on the host.

Classification: 
 (A) According to causative agents:

1. antibacterial 
2. antifunal
3. antiviral
4. antiprotozoal
5. antihelmentics 

in turn; antibacterial could be classified by their action:

• Bacteriostatics: which inhibit bacterial growth
• bactericidal: kill the bacteria

important note: depending on the dose; the drug could be converted from bacteriostatics to bactericidal; meaning that at high dose at high dose they are converted to bactericidal and in low dose or normal dose they are bacteriostatics.

(B) According to the spectrum of activity: 

1. narrow spectrum
2. extended spectrum 
3. broad spectrum 

General Principles of chemotherapy: 

1. making the diagnosis:  means to know exactly the type of infection, the organism responsible for that & sensitivity testing.
2. removal of the barrier: make it easy for the drug to penetrate and to go to site of infaction
3. decide whether chemotherapy is really necessary: 
4. select the best drug: meaning that the drug should be very specific to the infection; keeping in mined the condition of the immune system of the patient; pregnancy & lactating 
5. the cost: the drug should be very effective and do not cost very much
6. optimum dose and frequency: this done by knowing the pharmacokientics of the drug

Important Problem we could face by using antibiotics:

1. drug resistence 
2. super infection
3. drug-drug interaction
4. adverse effect