Name of the H1 Antihistamines Antiemetic Drugs
- Promethazine
- Diphenhydramine
- Dimenhydrinate
- Cyclizine
- Doxylamine
- Meclozine
- Cinnarizine
1.Promethazine
| Promethazine |
| Availability: Injection: 25 mg/ml and 50 mg/ml in 1-ml ampules and 1- and 10-ml vials Suppositories: 12.5 mg, 25 mg, 50 mg Syrup: 6.25 mg/5 ml Tablets: 12.5 mg, 25 mg, 50 mg |
| Indications and dosages Type 1 hypersensitivity reaction Adults: 25 mg P.O. or P.R. at bedtime or 12.5 mg P.O. before meals and at bedtime. Or 25 mg I.M. or I.V.; may repeat in 2 hours. Children older than age 2: 25 mg P.O. or P.R. at bedtime or 6.25 to 12.5 mg P.O. t.i.d. |
| Motion sickness Adults: Initially, 25 mg P.O. or P.R. 30 to 60 minutes before traveling; may repeat 8 to 12 hours later if needed. On successive travel days, 25 mg P.O. or P.R. b.i.d. (on arising and before evening meal). Children older than age 2: 12.5 to 25 mg P.O. or P.R. b.i.d. |
| Sedation Adults: 25 to 50 mg P.O., I.M., I.V., or P.R. at bedtime Children older than age 2: 12.5 to 25 mg P.O. or P.R. at bedtime |
| Adjunct to preoperative or postoperative analgesia Adults: 25 to 50 mg P.O., P.R., I.M., or I.V. given with appropriately reduced dosage of narcotic or barbiturate and required dosage of belladonna alkaloid Children older than age 2: 0.5 mg/lb P.O., P.R., I.M., or I.V., given with appropriately reduced dosage of narcotic or barbiturate and required dosage of belladonna alkaloid |
| Nausea Adults: 25 mg P.O. or P.R.; may repeat doses of 12.5 to 25 mg P.O. or P.R. q 4 to 6 hours p.r.n. Or 12.5 to 25 mg I.M. or I.V.; may repeat q 4 hours p.r.n. Children older than age 2: 25 mg or 0.5 mg/lb P.O. or P.R.; may repeat doses of 12.5 to 25 mg P.O. or P.R. q 4 to 6 hours p.r.n. May give I.M. or I.V. as no more than half of adult dosage. Know that drug should not be given if cause of vomiting is unknown. |
Mechanism of Action:
Blocks effects but not release of histamine and exerts strong alphaadrenergic effect. Also inhibits chemoreceptor trigger zone in medulla and alters dopamine effects by indirectly reducing reticular stimulation in CNS.
Pharmacokinetics
Metabolism
- Metabolized by hepatic P450 enzyme CYP2D6
- Metabolites: Promethazine sulfoxide and glucuronides (inactive)
Elimination
- Dialyzable: No
- Half-life: 10 hr (IM); 9-16 hr (IV); 16-19 hr (syrup)
- Excretion: Urine (major), feces (minor)
Administration
- Don’t give I.V. at concentrations greater than 25 mg/ml or faster than 25 mg/minute.
- Use light-resistant covering for I.V. drug. 2Inject I.M. deep into large muscle. Don’t give by subcutaneous route.
Contraindications
- Hypersensitivity to drug
- Previous idiosyncratic reaction to phenothiazines
- Coma
- Intra-arterial and subcutaneous injection
- Children younger than age 2
Precautions :
- Cardiovascular or hepatic disease, seizures, bone marrow depression, narrow-angle glaucoma, prostatic hypertrophy, stenosing peptic ulcer, pyloroduodenal or bladder neck obstruction
- CNS depression caused by narcotics, barbiturates, general anesthesia, tranquilizers, or alcohol
- Pregnant or breastfeeding patients.
Adverse reactions
- CNS: confusion, disorientation, fatigue, marked drowsiness, sedation, dizziness, extrapyramidal reactions, insomnia, nervousness, neuroleptic malignant syndrome
- CV: hypertension, hypotension, bradycardia, tachycardia
- EENT: blurred vision, diplopia, tinnitus
- GI: constipation, dry mouth
- Hematologic: blood dyscrasias
- Hepatic: cholestatic jaundice
- Respiratory: respiratory depression
- Skin: photosensitivity, rash
- Other: hypersensitivity reaction
Patient monitoring
- Monitor neurologic status. Stay alert for signs and symptoms of neuroleptic malignant syndrome (high fever, sweating, unstable blood pressure, stupor, muscle rigidity, and autonomic dysfunction).
- In long-term therapy, assess for other adverse CNS effects, including extrapyramidal reactions.
- Monitor CBC and liver function tests.
Patient teaching
- Teach patient to recognize and immediately report signs and symptoms of hypersensitivity reaction or neuroleptic malignant syndrome.
- Tell patient about drug’s other significant neurologic effects. Instruct him to contact prescriber if these occur.
- Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration, vision, alertness, and motor skills.
- As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, herbs, and behaviors mentioned above.
Nursing Considerations
- Use promethazine cautiously in children and elderly patients because they may be more sensitive to its effects, patients with cardiovascular disease or hepatic dysfunction because of potential adverse effects, patients with asthma because of anticholinergic effects, and patients with seizure disorders or those who take drugs that may affect seizure threshold because drug may lower seizure threshold.
- Inject I.M. form deep in
- Give I.V. injection at no more than 25 mg/ min; rapid I.V. administration may produce a transient drop in blood pressure.
- Monitor patient’s hematologic status as ordered because promethazine may cause bone marrow depression, especially when used with other known marrow-toxic agents. Assess patient for signs and symptoms of infection or bleeding.
- Be aware that patient shouldn’t have intradermal allergen tests within 72 hours of receiving promethazine because drug may significantly alter flare response.
2.Diphenhydramine
| Diphenhydramine |
| Availability : Capsules: 25 mg, 50 mg Elixir: 12.5 mg/5 ml Injection: 10 mg/ml, 50 mg/ml Strips (orally disintegrating): 12.5 mg, 25 mg Syrup: 12.5 mg/5 ml Tablets: 25 mg, 50 mg Tablets (chewable): 12.5 mg, 25 mg Tablets (orally disintegrating): 12.5 mg |
| Indications and dosages Allergy symptoms caused by histamine release (including anaphylaxis, seasonal and perennial allergic rhinitis, and allergic dermatoses); nausea; vertigo Adults and children over age 12: 25 to 50 mg P.O. q 4 to 6 hours, or 10 to 50 mg I.V. or I.M. q 2 to 3 hours p.r.n. (Some patients may need up to 100 mg.) Don’t exceed 400 mg/day. Children ages 6 to 12: 12.5 to 25 mg P.O. q 4 to 6 hours, or 1.25 mg/kg (37.5 mg/m2) I.M. or I.V. q.i.d. Don’t exceed 150 mg/day. Children ages 2 to 5: 6.25 mg P.O. q 4 to 6 hours. Don’t exceed 37.5 mg/day. |
| Cough Adults: 25 mg P.O. q 4 hours p.r.n. Don’t exceed 150 mg/day. Children ages 6 to 12: 12.5 mg P.O. q 4 hours. Don’t exceed 75 mg/day. Children ages 2 to 5: 6.25 mg P.O. q 4 hours. Don’t exceed 37.5 mg/24 hours |
| Dyskinesia; Parkinson’s disease Adults: Initially, 25 mg P.O. t.i.d.; may be increased to a maximum of 50 mg q.i.d |
| Mild nighttime sedation Adults: 50 mg P.O. 20 to 30 minutes before bedtime |
Mechanism of Action:
Interferes with histamine effects at histamine1-receptor sites; prevents but doesn’t reverse histamine-mediated response. Also possesses CNS depressant and anticholinergic properties.
Pharmacokinetics
- Metabolized by liver (first pass)
- Half-life: 5 hr (children); 9 hr (adults); 13.5 hr (elderly)
- Excretion: Urine (50-75%), mainly as metabolites
Administration
- For motion sickness, administer 30 minutes before activity.
- For I.V. use, check compatibility before mixing with other drugs.
- Inject I.M. dose deep into large muscle mass; rotate sites.
- Discontinue drug 4 days before allergy skin testing to avoid misleading results. 2Don’t give within 14 days of MAO inhibitors.
Contraindications
- Hypersensitivity to drug
- Alcohol intolerance
- Acute asthma attacks
- MAO inhibitor use within past 14 days
- Breastfeeding
- Neonates, premature infants
Precautions :
- Severe hepatic disease, angle-closure glaucoma, seizure disorders, prostatic hypertrophy, cardiovascular disease, hyperthyroidism
- Elderly patients
- Pregnant patients (safety not established)
- Children younger than age 2 (safety not established).
Adverse reactions
- CNS: drowsiness, dizziness, headache, paradoxical stimulation (especially in children)
- CV: hypotension, palpitations, tachycardia
- EENT: blurred vision, tinnitus GI: diarrhea, constipation, dry mouth
- GU: dysuria, urinary frequency or retention
- Skin: photosensitivity
- Other: decreased appetite, pain at I.M. injection site
Patient monitoring
- Monitor cardiovascular status, especially in patients with cardiovascular disease.
- Supervise patient during ambulation. Use side rails as necessary.
Patient teaching
- Advise patient to avoid alcohol and other depressants such as sedatives while taking drug.
- Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration and alertness.
- As appropriate, review all other significant adverse reactions and interactions, especially those related to the drugs, tests, herbs, and behaviors mentioned above
Nursing Considerations
- Expect to give parenteral form of diphenhydramine only when oral ingestion isn’t possible.
- Keep elixir container tightly closed. Protect elixir and parenteral forms from light.
- Expect to discontinue drug at least 72 hours before skin tests for allergies because drug may inhibit cutaneous histamine response, thus producing false-negative results. .
3.Dimenhydrinate
| Dimenhydrinate |
| Availability : Injection: 50 mg/ml Tablets: 50 mg Tablets (chewable): 50 mg |
| Indications and dosages Prevention and treatment of nausea, vomiting, dizziness, and vertigo Adults and children ages 12 and older: 50 to 100 mg P.O. q 4 hours (not to exceed 400 mg/day), or 50 mg I.M. or I.V. q 4 hours p.r.n. Children ages 6 to 12: 25 to 50 mg P.O. q 6 to 8 hours (not to exceed 150 mg/ day), or 1.25 mg/kg I.M. (37.5 mg/m2) q 6 hours p.r.n. Children ages 2 to 6: 12.5 to 25 mg P.O. q 6 to 8 hours (not to exceed 75 mg/day |
Mechanism of Action:
May inhibit vestibular stimulation and labyrinthine stimulation and function by acting on the otolith system and, with larger doses, on the semicircular canals.
Administration:
- For I.V. use, dilute with dextrose 5% in water or normal saline solution.
- Give each 50-mg I.V. dose over 2 minutes.
- Don’t administer by I.V. route to premature or low-birth-weight infants. Solution contains benzyl alcohol, which can cause fatal “gasping” syndrome.
Contraindications
- Hypersensitivity to drug or tartrazine
- Alcohol intolerance
Precautions:
- Angle-closure glaucoma, seizure disorders, prostatic hypertrophy
- Children younger than age 2.
Pharmacokinetics
- Half-Life: unknown, (half-life of diphenhydramine is about 3.5 hr)
- Duration: 3-6 hr Onset: 20-30 min (IM); 15-30 min (PO); almost immediately (IV)
- Bioavailability: Well, absorbed
- Metabolism: Extensively metabolized in the liver, based on data for diphenhydramine
- Excretion: Principally in urine (as metabolites)
Adverse reactions
- CNS: drowsiness, dizziness, headache, paradoxical stimulation (in children)
- CV: hypotension, palpitations
- EENT: blurred vision, tinnitus
- GI: diarrhea, constipation, dry mouth
- GU: dysuria, urinary frequency
- Skin: photosensitivity Other: decreased appetite, pain at I.M. site
Patient monitoring
- Assess for lethargy and drowsiness.
- Monitor for dizziness, nausea, and vomiting (possible indicators of drug toxicity).
Patient teaching
- To prevent motion sickness, advise patient to take drug 30 minutes before traveling and to repeat dose before meals and at bedtime.
- Instruct patient to avoid driving and other hazardous activities until he knows how drug affects concentration and alertness.
- Caution patient to avoid alcohol and sedative-hypnotics during therapy.
- As appropriate, review all other significant adverse reactions and interactions, especially those related to the drugs, tests, and behaviors mentioned above.
Nursing Considerations
- Monitor patients with prostatic hyperplasia, stenosing peptic ulcer, pyloroduodenal obstruction, bladder neck obstruction, angle-closure glaucoma, bronchial asthma, or cardiac arrhythmias for worsening of these conditions caused by anticholinergic effects.
- Monitor elderly patients for increased sensitivity to dimenhydrinate, such as excessive drowsiness, confusion, and restlessness.
- Assess patients, especially children and elderly patients, for evidence of paradoxical stimulation, such as nightmares, unusual excitement, nervousness, restlessness, or irritability.
- Store parenteral drug at 15° to 30° C (59° to 86° F); don’t freeze.
4.Cyclizine
| Cyclizine |
| Availability : Tablet 25mg ,50mg |
| Indications and Dosages To prevent postoperative vomiting I.M. INJECTION Adults and adolescents. 50 mg 15 to 30 min before surgery ends; then every 4 to 6 hr, p.r.n., for first few postoperative days. Children ages 6 to 12. 25 mg 15 to 30 min before surgery ends; then t.i.d., p.r.n., for first few postoperative days. Children up to age 6. 12.5 mg 15 to 30 min before surgery ends; then t.i.d., p.r.n., for first few postoperative days. |
| To prevent and treat motion sickness TABLETS Adults and adolescents. 50 mg 30 min before travel; then every 4 to 6 hr, p.r.n. Maximum: 200 mg daily. Children ages 6 to 12. 25 mg 30 min before travel; then every 6 to 8 hr, p.r.n. Maximum: 75 mg daily. I.M. INJECTION Adults and adolescents. 50 mg every 4 to 6 hr, p.r.n. Children. 1 mg/kg t.i.d., p.r.n |
Mechanism of Action
May act centrally on the vomiting center by blocking chemoreceptor trigger zones. Cyclizine also may reduce the sensitivity of the labyrinthine apparatus in the inner ear.
Pharmacokinetics
- Onset: 30 to 60 minutes, depending on dose
- Duration: 4 to 6 hr
- Metabolism: Hepatic
- Half-life elimination: 14 hr (cyclizine); 24hr (norcyclizine)
- Excretion: Urine (<1% unchanged)
- Vd: 17 L/kg
Contraindications
Hypersensitivity to cyclizine or its components, shock
Precautions:
- May have hypotensive effects, which may be confusing or dangerous in postoperative patients
- May produce drowsiness; caution while driving or performing other tasks requiring alertness
Adverse Reactions :
- CNS: Dizziness, drowsiness, euphoria, excitation, hallucinations, insomnia, nervousness, restlessness, seizures (in children), vertigo
- CV: Hypotension, palpitations, tachycardia
- EENT: Blurred vision; diplopia; dry mouth, nose, and throat; tinnitus
- GI: Anorexia, constipation, diarrhea, nausea, vomiting
- GU: Urinary frequency and hesitancy, urine retention
- SKIN: Jaundice, rash, urticaria
Nursing Considerations :
Help patient with ambulation, and take safety precautions to prevent injury from falls if drowsiness or dizziness occurs. Don’t schedule allergen skin tests until at least 5 days after stopping cyclizine; drug may interfere with test results.
Patient Teaching:
- Urge patient to avoid alcohol and other CNS depressants during cyclizine therapy.
- Advise patient to ask for help with ambulation if he feels drowsy or dizzy
5.Doxylamine
| Doxylamine |
| Availability : Tablet ,25ml, syrup 9.78 mg/3mL |
| Indications and Dosages ØInsomnia 25 mg PO qHS PRN 30 min before bedtime |
| Contraindications Hypersensitivity Children <12 years Coadministration with any other product containing doxylamine |
Mechanism of Action
Competes for H1-receptor sites on target cells; has anticholinergic effects, which depresses labyrinthine function, blocks chemoreceptor trigger zone, and diminishes vestibular stimulation
Pharmacokinetics
Absorption
- Peak Plasma Time: 2-3 hr
- Peak Plasma Concentration: 100 ng/mL
Elimination
- Half-Life: 10-12 hr
- Excretion: Urine
Side –effects
- Confusion, hallucinations.
- Severe dizziness or drowsiness; or
- Little or no urinating.
Common side effects of doxylamine may include:
- Blurred vision.
- Dry mouth , nose, or throat;
- Constipation
- Mild dizziness or drowsiness.
Warnings
- Do not exceed 2 weeks of use.
- This medication contains doxylamine. Do not take Unisom if you are allergic to doxylamine or any ingredients contained in this drug.
- Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately
Cautions
- May cause CNS depression, which may impair physical and mental activities
- Not to exceed 2 weeks of use
- Caution in asthma , glaucoma , enlarged prostate , cardiovascular disease, respiratory disease, or thyroid dysfunction
- Avoid use in the elderly because of the high incidence of anticholinergic effects
- Clearance reduced with advanced age, greater risk of confusion, dry mouth, constipation, and other anticholinergic effects and toxicity
- May exacerbate existing lower urinary conditions or benign prostatic hyperplasia
- Tolerance develops when used as hypnotic
Administration
- For insomnia (adults and children 12 and older): 25 to 50 mg orally at bedtime as needed, dosed 30 minutes before sleep.
- For allergy symptoms (adults and children 12 and older): 12.5 mg orally every 4 to 6 hours as needed, with a maximum dosage of 75 mg daily.
6.Meclozine
| Meclozine |
| Availability: Tablets: 12.5 mg, 25 mg, 50 mg Tablets (chewable): 25 mg |
| Indications and dosages Ø Motion sickness Adults: 25 to 50 mg P.O. 1 hour before travel. May repeat q 24 hours for duration of travel. |
| Vertigo associated with diseases affecting the vestibular system Adults: 25 to 100 mg |
Mechanism of Action
May inhibit nausea and vomiting by reducing sensitivity of labyrinthine apparatus and blocking cholinergic synapses in the brain’s vomiting center
Contraindications
Hypersensitivity to drug
Administration
Know that tablets may be chewed or swallowed whole.
Precautions:
- Prostatic hypertrophy, stenosing peptic ulcer, bladder neck obstruction, pyloroduodenal obstruction, arrhythmias, angle-closure glaucoma, bronchial asthma
- Pregnant or breastfeeding patients
- Children (younger than age 12).
Pharmacokinetics
Absorption
- Onset: 30-60 min
- Duration: 12-24 hr
- Peak plasma time: 3 hr
Distribution
Vd: 7 L/kg
Metabolism
In vitro study found CYP2D6 the dominant metabolic enzyme
Elimination
- Half-life: 5 hr
- Excretion: Urine, feces
Adverse reactions
- CNS: drowsiness, fatigue, confusion, excitement, euphoria, nervousness, restlessness, insomnia, vertigo, visual and auditory hallucinations, seizures
- CV: hypotension, palpitations, tachycardia
- EENT: blurred vision, diplopia, tinnitus, dry nose, dry throat
- GI: nausea, vomiting, diarrhea, constipation, dry mouth, anorexia
- GU: difficulty urinating, urinary retention, urinary frequency
- Skin: rash, urticaria
Patient monitoring
- Discontinue drug, as ordered, at least 4 days before skin testing.
- Know that drug has anticholinergic effects.
Patient teaching
- Tell patient to take as prescribed to minimize adverse effects.
- Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration and alertness.
- Advise patient to relieve dry mouth with hard candy or frequent sips of fluids.
- As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, and behaviors mentioned above.
Nursing Considerations
- Use meclizine cautiously in patients with asthma, glaucoma, or prostate gland enlargement.
- Be aware that drug may mask signs of brain tumor, intestinal obstruction, or ototoxicity
7.Cinnarizine
| Cinnarizine |
| Availability: Tablet 15 mg |
| Indications and dosages Vestibular symptoms: Adult, elderly and children over 12 years: Two tablets three times a day Children 5-12 years: one tablets three times a day |
| Motion sickness: Adult, elderly and children over 12 years: Two tablets two hours before travel and one tablet every eight hours during journey if necessary, Children 5-12 years: one tablets two hours before travel and half tablet every eight hours during journey if necessary |
Mechanism of Action:
Cinnarizine is a piperazine derivative with the action and uses of the antihistamines
Administration:
Cinnarizine should preferably be taken after meals. The tablets may be sucked, chewed or swallowed whole with water
Contraindication:
Hypersensitivity to the active substance
Pharmacokinetics
- Absorption: it is relatively slow, peak serum concentration occurring after 2.5 to 4 hours
- Metabolism: it is metabolised in N-dealkylation being the major pathway.
- Elimination: faeces, the rest in the urine
- Half-life: –4 to 24 hours
Precautions
- You are allergic to this medication or any of the other ingredients of this medication
- You are pregnant, planning to become pregnant, or breastfeeding
- You are taking any other medications, including supplements, traditional medications and herbal remedies.
- Medical conditions such as Parkinson Disease, liver and renal disease, porphyria (rare inherited blood disorder)
Side-effects
- Swollen face/eyes/lips/tongue
- Difficulty in breathing
- Itchy skin rashes over your whole body
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
Stories are the threads that bind us; through them, we understand each other, grow, and heal.
JOHN NOORD
Connect with “Nurses Lab Editorial Team”
I hope you found this information helpful. Do you have any questions or comments? Kindly write in comments section. Subscribe the Blog with your email so you can stay updated on upcoming events and the latest articles.
