Name of the Barbiturates Drugs
- Phenobarbital
- Mephobarbital
- Primidone
1.PHENOBARBITAL
| Phenobarbital |
| Availability: Elixir: 20 mg/5 mL. Oral Solution: 20 mg/5 mL. Injection Solution: 65 mg/mL, 130 mg/mL. Tablets: 15 mg, 30 mg, 60 mg, 100 mg |
| Administration/handling: IV Reconstitution : May give undiluted or may dilute with NaCl. Rate of administration : Adequately hydrate pt before and immediately after drug therapy (decreases risk of adverse renal effects). • Do not inject IV faster than 30 mg/min for children and 60 mg/ min for adults. Too-rapid IV may produce severe hypotension, marked respiratory depression. • Inadvertent intra-arterial injection may result in arterial spasm with severe pain, tissue necrosis. Extravasation in SQ tissue may produce redness, tenderness, tissue necrosis. Storage : Store vials at room temperature. |
| IM : Do not inject more than 5 mL in any one IM injection site (produces tissue irritation). • Inject deep IM into large muscle mass |
| PO : Give without regard to food. • Tablets may be crushed. • Elixir may be mixed with water, milk, fruit juice. |
| Status Epilepticus: IV: Adults, elderly, children: 15 mg/kg as a single dose. Children: 15–20 mg/ kg (Maximum: 1,000 mg) over 10 min; may repeat after 15 min (Maximum: 40 mg/kg) |
| Seizure Control (Maintenance) Note: Maintenance dose usually starts 12 hrs after loading dose. PO, IV: Adults, elderly, children older than 12 yrs: 2 mg/kg/day in divided doses. Children 5–12 yrs: 4–6 mg/kg/day in divided doses. Children 1–5 yrs: 6–8 mg/ kg/day in divided doses. Children younger than 1 yr: 5–6 mg/kg/day in 1–2 divided doses. Neonates: 3–4 mg/kg/day given once daily |
Mechanism of Action:
Depresses sensory cortex, decreases motor activity, alters cerebellar function. Therapeutic Effect: Induces drowsiness, sedation, anticonvulsant activity.
Indications:
- onic-clonic (grand mal) and partial seizures; febrile seizures in children
- Status epilepticus
- Short-term treatment of insomnia
- Daytime sedation
- Preoperative sedation
- Off-label uses : prevention and treatment of hyperbilirubinemia
Cautions & Contraindications:
- Hypersensitivity to phenobarbital, other barbiturates
- Porphyria
- Dyspnea or airway obstruction
- Use in nephritic pts (large doses)
- Severe hepatic impairment
- Pts with history of sedative/hypnotic addiction.
- Intra-arterial or SQ administration.
- Cautions: renal/ hepatic impairment
- Acute/chronic pain
- Depression
- Suicidal tendencies
- History of drug abuse Elderly pts, debilitated pts, children, hemodynamically unstable pts, hypoadrenalism, respiratory disease.
Side- Effects:
- CNS: Anxiety, depression, dizziness, drowsiness, headache, irritability, lethargy, mood changes, paradoxical stimulation, sedation, vertigo
- CV: Hypotension, sinus bradycardia
- EENT: Miosis, ptosis
- GI: Constipation, diarrhea, nausea, vomiting
- GU: Decreased libido, impotence, sexual dysfunction
- Musculoskeletal : Arthralgia, bone tenderness
- RESP: Bronchospasm, respiratory depression
- SKIN: Dermatitis, photosensitivity, rash, urticaria
- Other: Injection site phlebitis (I.V.), physical and psychological dependence
Nursing Considerations
Baseline assessment
- Assess B/P, pulse, respirations immediately before administration.
- Hypnotic: Raise bed rails, provide environment conducive to sleep (back rub, quiet environment, low lighting). Seizures: Review history of seizure disorder (length, presence of auras, LOC).
- Observe for recurrence of seizure activity. Initiate seizure precautions.
Intervention/evaluation
- Monitor CNS status, seizure activity, hepatic/renal function, respiratory rate, heart rate, B/P.
- Monitor for therapeutic serum level.
- Neurologic assessments may be inaccurate until drug has properly cleared the body.
- Therapeutic serum level: 10–40 mcg/mL; toxic serum level: greater than 40 mcg/mL.
Patient/family teaching
- Avoid alcohol, limit caffeine.
- May be habit-forming.
- Do not discontinue abruptly.
- May cause dizziness/drowsiness; avoid tasks that require alertness, motor skills until response to drug is established
2.MEPHOBARBITAL
| Mephobarbital |
| Availability: tablet : 32mg, 50mg,100mg |
| Administration & Handling : Mephobarbital tablets are best taken at bedtime if seizures generally occur at night, and during the day if attacks are diurnal. Treatment should be started with a small dose which is gradually increased over four or five days until the optimum dosage is determined. Store at 25° C (77° F) |
| To treat seizures : Tablets : Adults. 400 to 600 mg daily as a single dose or in divided doses, usually beginning with low dose and increasing over 4 to 5 days until optimum dosage is determined. Children over age 5. 32 to 64 mg t.i.d. or q.i.d; Children under age 5. 16 to 32 mg t.i.d. or q.i.d. |
| To provide sedation : Tablets : Adults. 32 to 100 mg t.i.d. or q.i.d; Children. 16 to 32 mg t.i.d. or q.i.d. |
Mechanism of Action:
May reduce seizure activity by reducing transmission of monosynaptic and polysynaptic nerve impulses, which decreases excitability in nerve cells. As a sedative, mephobarbital inhibits upward conduction of nerve impulses to the reticular formation of the brain, which disrupts impulse transmission to the cortex. As a result, mephobarbital depresses the CNS and produces drowsiness, hypnosis, and sedation
Indications:
- Sedative for the relief of anxiety, tension, and apprehension
- Anticonvulsant for the treatment of grand mal and petit mal epilepsy.
Cautions & Contraindications:
- Hepatic disease or failure
- History of addiction to sedatives or hypnotics
- Hypersensitivity to mephobarbital, other barbiturates, or their components; nephritis; porphyria;
- Severe respiratory disease with obstruction or dyspnea
Metabolism and Half- Life:
Approximately 50% of an oral dose of mephobarbital is absorbed from the gastrointestinal tract. Therapeutic plasma concentrations for mephobarbital have not been established nor has the half-life been determined. Following oral administration, the onset of action of the drug is 30 to 60 minutes and the duration of action is 10 to 16 hours.
Drug Interactions:
- Acetaminophen: possibly decreased effects of acetaminophen (with long-term mephobarbital use)
- Anesthetics (halogenated hydrocarbon): increased risk of hepatotoxicity (with long-term mephobarbital use)
- CNS depressants: increased CNS depression
- Oral anticoagulants: possibly decreased therapeutic effects of anticoagulants, possibly increased risk of bleeding when mephobarbital is discontinued
- Tricyclic antidepressants: possibly decreased therapeutic effects of tricyclic antidepressants
- Alcohol use: increased CNS depression
Side- effects:
- CNS: Agitation, anxiety, ataxia, confusion, delusions, depression, dizziness, drowsiness, fever, hallucinations, headache, insomnia, irritability, nervousness, nightmares, paradoxical stimulation, seizures, syncope, tremor
- CV: Orthostatic hypotension
- EENT: Vision changes
- GI: Anorexia, constipation, hepatic dysfunction, nausea, vomiting
- Musculoskeletal : Arthralgia, bone pain, muscle twitching or weakness
- RESP: Respiratory depression
- SKIN: Exfoliative dermatitis, rash, Stevens- Johnson syndrome
- Other: Physical and psychological dependence, weight loss
Nursing Considerations
- Observe patient for signs of physical and psychological dependence, especially with prolonged use at high doses.
- Observe for signs of chronic barbiturate intoxication, including confusion, insomnia, poor judgment, slurred speech, and unsteady gait.
- Assess for paradoxical stimulation in patient who receives drug for acute or chronic pain.
- Expect to taper mephobarbital gradually when discontinuing. Be aware that withdrawal symptoms can be severe and may cause death.
- Mild signs and symptoms may include anxiety, muscle twitching, nausea, orthostatic hypotension, and progressive weakness and may appear 8 to 12 hours after last dose. More severe signs include delirium and seizures
Patient teaching
- Advise patient to take mephobarbital exactly as prescribed. Caution him not to stop taking drug abruptly because of possible withdrawal symptoms and, for epileptic patients, seizures.
- Instruct patient to avoid alcohol, sleeping pills, and other sedatives while taking mephobarbital because of the risk of increased CNS depression.
- Advise patient to avoid hazardous activities until CNS effects of drug are known.
- Advise patient to change position slowly to minimize orthostatic hypotension.
- Urge patient to report confusion, fever, rash, or severe dizziness.
3.PRIMIDONE
| Primidone |
| Availability: Suspension: 250 mg/5 ml; Tablets: 50 mg, 250 mg |
| Administration/handling: PO • Give with food to minimize GI effects; Don’t stop therapy suddenly. Dosage must be tapered.; Know that drug may be given alone or with other anticonvulsants |
| Seizure Control : PO: Adults, elderly, children 8 yrs and older: Initially, 100–125 mg/ day at bedtime for days 1–3. Days 4–6: 100–125 mg twice daily. Days 7–9: 100–125 mg 3 times/day. Usual dose: 750–1,500 mg/day in 3–4 divided doses. Maximum: 2 g/day. Children younger than 8 yrs: Initially, 50 mg/day at bedtime for days 1–3. Days 4–6: 50 mg twice daily. Days 7–9: 100 mg twice daily. Usual dose: 10–25 mg/ kg/day (375–750 mg) in 3–4 divided doses. Neonates: 12–20 mg/kg/day in divided doses 2–4 times/day |
| Essential Tremor (Off-label) : 50-62.5 mg PO qDay; as tolerated, may gradually increase dose based on response and tolerability, by 62.5-125 mg PO every 1-3 days or by 250 mg/week, administered in 2 or 3 divided doses; not to exceed 750 mg/day. |
Mechanism of Action:
Prevents seizures by decreasing excitability of neurons and increasing motor cortex’s threshold of electrical stimulation
Indications:
- Grand mal, psychomotor, or focal epileptic seizures
- Off-label uses : Benign familial (essential) tremor
Cautions & Contraindications:
- Hypersensitivity to primidone, phenobarbital
- Porphyria.
- Cautions: renal/hepatic impairment
- Pulmonary insufficiency
- Elderly pts, debilitated pts, children, hypoadrenalism
- Pts at risk for suicidal thoughts/behavior, depression
- History of drug abuse.
Metabolism and Half- Life:
Rapidly, usually completely absorbed following PO administration. Protein binding: 99%. Metabolized in liver to Phenobarbital. Minimal excretion in urine. Half-life: 3–6 hrs. (Phenobarbital: 2–5 days.)
Drug Interactions:
- Alcohol, other CNS depressants may increase effects.
- Valproic acid increases concentration, risk of toxicity.
- Strong CYP2C19 inducers may decrease concentration/effect.
- Strong CYP2C19 inhibitors may increase concentration/effect.
- May decrease effect of dolutegravir, oral contraceptives, tenofovir, voriconazole, warfarin
Side- Effects:
- Ataxia
- Dizziness
- Occasional: Anorexia, drowsiness, altered mental status, nausea, vomiting, paradoxical excitement.
- Rare: Rash.
- May increase risk of suicidal thoughts and behavior
Nursing Considerations
Baseline assessment
- Review history of seizure disorder (intensity, frequency, duration, LOC).
- Observe frequently for recurrence of seizure activity. Initiate seizure precautions.
Intervention/evaluation
- Monitor for changes in behavior, depression, suicidal ideation.
- Monitor CBC, neurologic status (frequency, duration, severity of seizures).
- Monitor for therapeutic serum level: 4–12 mcg/ mL; toxic serum level: more than 12 mcg/mL.
Patient/family teaching
- Do not abruptly discontinue medication after long-term use (may precipitate seizures).
- Strict maintenance of drug therapy is essential for seizure control.
- Avoid tasks that require alertness, motor skills until response to drug is established; drowsiness usually disappears during continued therapy.
- Slowly go from lying to standing.
- Avoid alcohol.
- Report depression, thoughts of suicide, unusual changes in behavior.
REFERENCES
- Robert Kizior, Keith Hodgson, Saunders Nursing Drug handbook,1st edition 2024, Elsevier Publications. ISBN-9780443116070
- McGraw Hill- Drug Handbook, Seventh Edition, 2013, McGraw Hill Education Publications,9780071799430.
- April Hazard, Cynthia Sanoski, Davi’s Drug Guide for Nurses -Sixteenth Edition 2019, FA Davis Company Publications,9780803669451.
- Jones and Bartlet, Pharmacology for Nurses, Second Edition, 2020, Jones and Bartlet Learning Publications, ISBN 9781284141986.
- Nursebro.com, Search – Nursebro
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