Download Roach: Introductory Clinical Pharmacology

Introduction to Clinical
Pharmacology
Chapter 29Anticonvulsants
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Anticonvulsants: Actions
• Benzodiazepines and barbiturates elevate
seizure threshold by decreasing postsynaptic
excitation
• Hydantoins stabilize hyperexcitability
postsynaptically in motor cortex of brain
• Oxazolidinediones decrease repetitive
synaptic transmission of nerve impulses
• Succinimides depress motor cortex creating
higher threshold before nerves react to
convulsive stimuli
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Anticonvulsants: Uses
• Used prophylactically to prevent seizures following
trauma, neurosurgery, or tumor
• Used in treatment of:
– Seizures of all types; neuropathic pain; biopolar
disorders; anxiety disorders
– Status epilepticus-continual seizure activity.
Ativan (lorazepam) is the drug of choice for this
condition. The effects of lorazepam last less than
1 hour, may need a longer lasting anticonvulsant
such as phenytoin (Dilantin) or phenobarbital to
continue to control the seizure
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Anticonvulsants: Adverse Reactions
• Central nervous system reactions: Drowsiness;
weakness; dizziness; headache; somnolence;
nystagmus; ataxia; slurred speech
– *CNS depression with phenobarbital
• Gastrointestinal reactions: Nausea; vomiting;
anorexia; constipation; diarrhea; gingival
hyperplasia-phenytoin
• Other: Skin rashes; pruritus; urticaria; urinary
frequency; serious skin reactions; hematologic
changes-pancytopenia with administration of
carbamazepine (Tegretol), felbamate (Felbatol) and
trimethadione (Tridione)
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Anticonvulsants: Contraindications
• Contraindicated in patients : Hypersensitive
to the drugs
– Phenytoin is contraindicated in patients
with sinus bradycardia; sinoatrial block;
Adams-Stokes syndrome; second and
third-degree atrioventricular (AV) block;
during pregnancy and lactation
– Ethotoin (Pegatone) is contraindicated in
patients with hepatic abnormalities
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Anticonvulsants: Contraindications
(cont’d)
– Succinimides are contraindicated in
patients with bone marrow depression or
hepatic or renal impairment
– Carbamazepine is contraindicated in
patients with bone marrow depression or
hepatic or renal impairment and during
pregnancy
– Valproic acid (Depakote) is not
administered to patients with renal
impairment or during pregnancy
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Anticonvulsants: Precautions
– Phenytoin is used cautiously in patients
with hypotension; severe myocardial
insufficiency; hepatic impairment
– Trimethadione is used with caution in
patients with eye disorders
– Miscellaneous anticonvulsants are used
cautiously in patients with glaucoma or
increased intraocular pressure; a history
of cardiac, renal or liver dysfunction; and
psychiatric disorders
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Anticonvulsants: Interactions
Interactant Drug
Effect of Interaction
Antibiotics/antifungals
Increased effect of the
anticonvulsant
Increased effect of the
anticonvulsant
Increased effect of the
anticonvulsant
Increased effect of the
anticonvulsant
Increased depressant
effect
Tricyclic
antidepressants
Salicylates
Cimetidine
Analgesics or alcohol
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Nursing Process: Assessment
• Preadministration assessment:
– Obtain vital signs at the time of the initial
assessment to provide baseline data
– Thorough patient history is necessary to
identify type of seizure disorder
– Primary health care provider may order
laboratory and diagnostic tests
– **See display 30.1
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Nursing Process: Assessment
• Ongoing assessment:
– Carefully document each seizure with
regard to time of occurrence, duration of
seizure, psychic or motor activity
occurring before, during, after seizure
– Dosage adjustments are based on
patient’s response to therapy, as well as
occurrence of adverse reactions
– Serum plasma levels of anticonvulsant
are measured regularly to monitor for
toxicity
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Nursing Process: Planning
• Expected outcomes for patient depend on
the type and severity of the seizure but may
include:
– optimal response to therapy
– Support of patient needs related to
management of adverse reactions
– Understanding of and compliance with
prescribed therapeutic regimen
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Nursing Process: Implementation
• Promoting an optimal response to therapy:
– Make notation on the care plan, as well as
informing all health care team members of the
importance of the drug
– Status epilepticus may result from abrupt
discontinuation of the drug, even when it is
being administered in small doses-MONITOR RR!
– Barbiturates:
• Monitor patient carefully during administration
of barbiturate, taking blood pressure and
observing respirations frequently
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Nursing Process: Implementation
• Promoting an optimal response to therapy
(cont’d):
– Benzodiazepines:
•Dosage of benzodiazepines is highly
individualized, increase the dosage
cautiously to avoid adverse reactions,
particularly in elderly and debilitated
patient
•Do not mix diazepam with other drugs
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Nursing Process: Implementation
• Promoting an optimal response to therapy
(cont’d):
– Hydantoins:
•Monitor serum concentrations of drug
on regular basis to detect signs of
toxicity
– Geriatric ALERT!
•BARBITURATES MAY PRODUCE MARKED
EXCITEMENT, DEPRESSION AND
CONFUSION IN ELDERLY
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Nursing Process: Implementation
• Monitoring and managing patient needs:
– Risk for injury:
• The nurse should assist the patient with all
ambulatory activities
• Use caution when giving an oral preparation
as aspiration of tablet, capsule, or liquid
may occur if patient experiences drowsiness
• Test swallowing ability of patient by offering
small sips of water before giving drug
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Nursing Alert
• Phenytoin may cause hematoogic changes
MONITOR FOR LEUKOPENIA, SWOLLEN GLANDS
• When administering phenytoin, monitor the patient for
s/s of drug toxicity-slurred speech, ataxia, lethargy,
dizziness, nausea, vomiting
– Plasma levels between 10-20 mcg/ml give optimal
anticonvulsant effect
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Nursing Process: Implementation
• Educating the patient and family:
– When patient receives diagnosis of epilepsy, nurse must
assist patient and family to adjust to diagnosis
– Instruct family members in care of patient before, during,
and after seizure
– Explain importance of restricting some activities until
seizures are controlled by drugs
– Assist patient to look for other modes of transportation in
order to continue typical activities or employment
– The nurse reviews adverse drug reactions associated with
the prescribed anticonvulsant with the patient and family
members
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Nursing Process: Implementation
• Educating the patient and family (cont’d):
– Hydantoins:
•Inform dentist and other primary health
care providers of use of this drug
•Brush and floss teeth after each meal
and make periodic dental appointments
for oral examination and care
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Nursing Process: Implementation
• Educating the patient and family (cont’d):
•Take medication with food to reduce GI
upset
•Thoroughly shake phenytoin suspension
immediately before use
•Do not take capsules that are
discolored
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Nursing Process: Implementation
• Educating the patient and family (cont’d):
•Notify primary health care provider if
any of the following occurs: Skin rash;
bleeding; swollen or tender gums;
yellowish discoloration of the skin or
eyes; unexplained fever; sore throat;
unusual bleeding or bruising; persistent
headache; malaise; or pregnancy
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Nursing Process: Implementation
• Educating the patient and family (cont’d):
– Succinimides:
•If GI upset occurs, take drug with food
or milk
•Notify primary health care provider if
any of the following occurs: Skin rash;
joint pain; unexplained fever; sore
throat; usual bleeding or bruising;
drowsiness; dizziness, blurred vision; or
pregnancy
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Nursing Process: Implementation
• Educating the patient and family (cont’d):
– Oxazolidinediones:
•Determine: Protective measures when
exposed to ultraviolet light, sunlight
•Notify primary care provider if following
reactions occur: Visual disturbances;
excessive drowsiness; dizziness; sore
throat; fever; skin rash; pregnancy;
malaise; easy bruising; epistaxis;
bleeding tendencies
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Nursing Process: Evaluation
• Therapeutic effect is achieved and convulsions are controlled
• No injury is evident
• Adverse reactions are identified, reported, and managed
successfully through appropriate nursing interventions
• Patient verbalizes the importance of complying with the
prescribed treatment regimen
• Patient verbalizes an understanding of treatment modalities
and the importance of continued follow-up care
• Patient and family demonstrate an understanding of the drug
regimen
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