promethazine

Blocks the effects of histamine.
Has inhibitory effect on the chemoreceptor trigger zone in the medulla, resulting in antiemetic properties.
Alters the effects of dopamine in the CNS.
Possesses significant anticholinergic activity.
Produces CNS depression by indirectly decreased stimulation of the CNS reticular system.

Therapeutic effects:

Relief of symptoms of histamine excess usually seen in allergic conditions.
Diminished nausea or vomiting.
Sedation.

Pharmacokinetics ⬆ ⬇

Absorption: Well absorbed after oral (88%) and IM administration; rectal administration may be less reliable. IV administration results in complete bioavailability.

Distribution: Widely distributed to tissues.

Metabolism/Excretion: Metabolized by the liver.

Half-Life: 9–16 hr.

Time/Action Profile ⬆ ⬇

(noted as antihistaminic effects; sedative effects last 2–8 hr)

ROUTE	ONSET	PEAK	DURATION
PO, IM	20 min	unknown	4–12 hr
Rectal	20 min	unknown	4–12 hr
IV	3–5 min	unknown	4–12 hr

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity;
Comatose patients;
Prostatic hypertrophy;
Bladder-neck obstruction;
Some products contain alcohol or bisulfites and should be avoided in patients with known intolerance;
Angle-closure glaucoma;
Pedi: Children 2 yr (may cause fatal respiratory depression).

Use Cautiously in:

Hypertension;
Cardiovascular disease;
Hepatic impairment;
Prostatic hypertrophy;
Glaucoma;
Asthma;
Sleep apnea;
Epilepsy;
Underlying bone marrow depression;
Pedi: Children >2 yr (use lowest effective dose and avoid concurrent respiratory depressants);
OB: Avoid chronic use during pregnancy;
Lactation: Safety not established in breastfeeding; Geri: Appears on Beers list. risk of anticholinergic adverse reactions in older adults, including falls, delirium, and dementia. Avoid use in older adults.

Adv. Reactions/Side Effects ⬆ ⬇

CV: bradycardia, hypertension, hypotension, tachycardia

Derm: photosensitivity, rash, severe tissue necrosis upon infiltration at IV site

EENT: blurred vision, diplopia, tinnitus

GI: constipation, dry mouth, hepatitis

Hemat: blood dyscrasias

Neuro: confusion, disorientation, sedation, dizziness, extrapyramidal reactions, fatigue, insomnia, nervousness, NEUROLEPTIC MALIGNANT SYNDROME

Interactions ⬆ ⬇

Drug-drug:

Additive CNS depression with other CNS depressants, including alcohol, other antihistamines, opioid analgesics, and other sedative/hypnotics.
Neuroleptic malignant syndrome can occur when used concurrently with antipsychotics.
Additive anticholinergic effects with other drugs possessing anticholinergic properties, including other antihistamines, antidepressants, atropine, haloperidol, other phenothiazines, quinidine, and disopyramide.
May precipitate seizures when used with drugs that lower seizure threshold.
Concurrent use with MAO inhibitors may result in ↑ sedation and anticholinergic side effects.

Route/Dosage ⬆ ⬇

Antihistamine

PO (Adults ): 6.25–12.5 mg 3 times/day and 25 mg at bedtime.
PO (Children ≥2 yr): 0.1 mg/kg/dose (not to exceed 12.5 mg) every 6 hr during the day and 0.5 mg/kg/dose (not to exceed 25 mg) at bedtime.
IM IV
(Adults ): 25 mg; may repeat in 2 hr.
(Children ≥2 yr): 0.125 mg/kg every 4–6 hr or 0.5 mg/kg at bedtime.

Antivertigo (Motion Sickness)

PO (Adults ): 25 mg 30–60 min before departure; may be repeated in 8–12 hr.
PO
(Children ≥2 yr): 0.5 mg/kg (not to exceed 25 mg) 30–60 min before departure; may be given every 12 hr as needed.

Sedation

PO
IM IV (Adults ): 25–50 mg; may repeat every 4–6 hr if needed.
PO
IM (Children >2 yr): 0.5–1 mg/kg (not to exceed 50 mg) every 6 hr as needed.

Nausea/Vomiting

PO
IM IV (Adults ): 12.5–25 mg every 4 hr as needed; initial PO dose should be 25 mg.
PO
IM IV (Children ≥2 yr): 0.25–1 mg/kg (not to exceed 25 mg) every 4–6 hr.

Availability ⬆ ⬇

(Generic available)

Tablets: 12.5 mg; 25 mg; 50 mg
Oral solutioncherry flavor: 6.25 mg/5 mL
Solution for injection: 25 mg/mL; 50 mg/mL
Suppositories: 12.5 mg; 25 mg; 50 mg
In combination with: codeine, dextromethorphan, and/or phenylephrine in a variety of cough and cold preparations.

Assessment ⬆ ⬇

Monitor BP, pulse, and respiratory rate frequently in patients receiving IV doses.
- Assess level of sedation after administration. Risk of sedation and respiratory depression are increased when administered concurrently with other drugs that cause CNS depression.
- Monitor patient for onset of extrapyramidal side effects (akathisia: restlessness; dystonia: muscle spasms and twisting motions; pseudoparkinsonism: mask-like face, rigidity, tremors, drooling, shuffling gait, dysphagia). Notify health care professional if these symptoms occur.
- Monitor for development of neuroleptic malignant syndrome (fever, respiratory distress, tachycardia, seizures, diaphoresis, hypertension or hypotension, pallor, tiredness, severe muscle stiffness, loss of bladder control). Notify health care professional immediately if these symptoms occur.
Assess for falls risk. Drowsiness, orthostatic hypotension, and motor and sensory instability increase risk. Institute prevention if indicated.
Geri: Assess for adverse anticholinergic effects (delirium, acute confusion, dizziness, dry mouth, blurred vision, urinary retention, constipation, tachycardia).
Allergy: Assess allergy symptoms (rhinitis, conjunctivitis, hives) before and periodically throughout course of therapy.
Antiemetic: Assess patient for nausea and vomiting before and after administration.
IV:
If administered IV, assess for burning and pain at IV site; may cause severe tissue injury. Avoid IV administration, if possible. If pain occurs, discontinue administration immediately.

Lab Test Considerations:

May cause false-positive or false-negative pregnancy test results.
- Evaluate CBC periodically during chronic therapy; blood dyscrasias may occur.
- May cause ↑ serum glucose.
- May cause false-negative results in skin tests using allergen extracts. Promethazine should be discontinued 72 hr before the test.

Implementation ⬆ ⬇

When administering promethazine concurrently with opioid analgesics, supervise ambulation closely to prevent injury from increased sedation.
PO: Administer with food, water, or milk to minimize GI irritation. Tablets may be crushed and mixed with food or fluids for patients with difficulty swallowing.
IM: Administer deep into well-developed muscle. SUBQ or inadvertent intra-arterial administration may cause severe tissue necrosis.

IV Administration:

Diluent: Dilute with 0.9% NaCl or D5W.Concentration: Doses should not exceed a concentration of 25 mg/mL. Administer through a large-bore vein through a running IV line into the most distal port. Slight yellow color does not alter potency. Do not use if precipitate is present.
Rate: Administer each 25 mg slowly, over at least 10–15 min (maximum rate = 25 mg/min). Rapid administration may produce a transient fall in BP.

Patient/Family Teaching ⬆ ⬇

Review dose schedule with patient. If medication is ordered regularly and a dose is missed, take as soon as remembered unless time for next dose. Pedi: Caution caregivers to use only the measuring device accompanying the liquid medication and not to use household measuring devices.
- May cause drowsiness. Caution patient to avoid driving or other activities requiring alertness until response to medication is known.
- Advise patient that frequent mouth rinses, good oral hygiene, and sugarless gum or candy may decrease dry mouth. Health care professional should be notified if dry mouth persists >2 wk.
- Caution patient to use sunscreen and protective clothing to prevent photosensitivity reactions.
- Advise patient to change positions slowly to minimize orthostatic hypotension. Protect from falls. Geriatric patients are at increased risk.
- Caution patient to avoid concurrent use of alcohol and other CNS depressants with this medication.
- Instruct patient to notify health care professional if sore throat, fever, jaundice, or uncontrolled movements are noted.
Rep: Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected or if breastfeeding.
Motion Sickness: When used as prophylaxis for motion sickness, advise patient to take medication at least 30 min and preferably 1–2 hr before exposure to conditions that may cause motion sickness.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

Action ⬆ ⬇