Sominex
diphenhydramine hydrochloride
Pharmacologic class: Ethanolamine derivative, nonselective histamine1-receptor antagonist
Therapeutic class: Antihistamine, antitussive, antiemetic, antivertigo agent, antidyskinetic
Pregnancy risk category B
Action
Interferes with histamine effects at histamine1-receptor sites; prevents but doesn't reverse histamine-mediated response. Also possesses CNS depressant and anticholinergic properties.
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
Dosage adjustment
• Elderly patients
Off-label uses
• Drug-induced extrapyramidal reactions
Contraindications
• Hypersensitivity to drug
• Alcohol intolerance
• Acute asthma attacks
• MAO inhibitor use within past 14 days
• Breastfeeding
• Neonates, premature infants
Precautions
Use cautiously in:
• 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).
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.
See Don't give within 14 days of MAO inhibitors.
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
Interactions
Drug-drug. Antihistamines, opioids, sedative-hypnotics: additive CNS depression
Disopyramide, quinidine, tricyclic antidepressants: increased anticholinergic effects
MAO inhibitors: intensified and prolonged anticholinergic effects
Drug-diagnostic tests. Skin allergy tests: false-negative results
Hemoglobin, platelets: decreased values
Drug-herbs. Angel's trumpet, jimson weed, scopolia: increased anticholinergic effects
Chamomile, hops, kava, skullcap, valerian: increased CNS depression
Drug-behaviors. Alcohol use: increased CNS depression
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.
promethazine hydrochloride
Pharmacologic class: Phenothiazine (nonselective)
Therapeutic class: Antihistamine, antiemetic, sedative-hypnotic
Pregnancy risk category C
FDA Box Warning
• Don't use promethazine in patients younger than age 2 due to potential for fatal respiratory depression. (Postmarketing cases of respiratory depression have been reported in these patients.)
• Use caution when administering to pediatric patients age 2 years and older. Preferably, use lowest effective dosage in these patients and avoid concurrent use of other drugs with respiratory depressant effects.
• Promethazine injection can cause severe chemical irritation and damage to tissue regardless of administration route. Irritation and damage can result from perivascular extravasation, unintentional intra-arterial injection, and intraneuronal or perineuronal infiltration.
• Adverse reactions to I.V. injection include burning, pain, thrombophlebitis, tissue necrosis, and gangrene. In some cases, surgical intervention, including fasciotomy, skin graft, or amputation, has been required.
• Because of risks of I.V. injection, preferred parenteral administration route is deep I.M. injection. Subcutaneous injection is contraindicated.
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.
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.
Contraindications
• Hypersensitivity to drug
• Previous idiosyncratic reaction to phenothiazines
• Coma
• Intra-arterial and subcutaneous injection
• Children younger than age 2
Precautions
Use cautiously in:
• 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.
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.
See Inject I.M. deep into large muscle. Don't give by subcutaneous route.
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
Interactions
Drug-drug. Anticholinergics: additive anticholinergic effects
CNS depressants: additive CNS depression
Epinephrine: reversal of epinephrine's vasopressor effects
MAO inhibitors: increased extrapyramidal effects
Drug-diagnostic tests. Glucose: increased level
Granulocytes, platelets, white blood cells: decreased counts
Pregnancy test: false-positive or false-negative result
Skin tests using allergen extracts: false-negative results
Drug-herbs. Betel nut: increased risk of extrapyramidal reactions
Evening primrose oil: increased risk of seizures
Kava: increased risk of adverse drug effects
Drug-behaviors. Alcohol use: additive CNS depression
Sun exposure: increased risk of photosensitivity
Patient monitoring
See 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
See 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.