Phentolamine Uses, Dosage, Side Effects & Warnings | DrugsAtlas
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DRUG NAME: Phentolamine
Therapeutic Class: Alpha-Adrenergic Blocking Agent
Subclass: Non-selective Alpha-Adrenergic Antagonist
Speciality: Critical Care Medicine
Schedule (India): Schedule H
Route(s): Intravenous, Intramuscular, Local Infiltration
Formulations Available in India:
- Injection: 10 mg/mL (ampoule)
- Note: Availability primarily in tertiary care hospitals; may require special procurement
INDICATIONS + DOSING — FOR CLINICIAN USE ONLY
Primary Indications (Approved / Standard in India)
1. Hypertensive Crisis due to Phaeochromocytoma
Used for diagnosis, preoperative preparation, and intraoperative blood pressure control during tumour manipulation.
| Step | Dose | Clinical Notes |
| Starting dose | 2.5–5 mg IV bolus | Administer over 1 minute |
| Titration | Repeat 2.5–5 mg IV every 5–15 minutes | Based on blood pressure response |
| Usual maintenance dose | 1–5 mg IV every 4–6 hours | Titrated to target BP |
| Maximum dose | No absolute ceiling; guided by clinical response | Monitor closely for hypotension |
Key Clinical Notes:
- Continuous BP and HR monitoring mandatory during administration
- Have noradrenaline/phenylephrine available for managing excessive hypotension
- Beta-blocker should only be added after adequate alpha-blockade to prevent unopposed alpha-mediated vasoconstriction
2. Local Tissue Ischaemia following Vasopressor Extravasation (Noradrenaline/Dopamine)
| Step | Dose | Clinical Notes |
| Starting dose | 5–10 mg diluted in 10–15 mL normal saline | Infiltrate directly into affected area using fine needle |
| Titration | Not applicable | Single infiltration typically sufficient |
| Usual maintenance dose | Not applicable | Repeat only if clinical signs persist |
| Maximum dose | 10 mg per episode | May repeat based on clinical judgement |
Key Clinical Notes:
- Most effective when administered within 12 hours of extravasation
- Infiltrate throughout the ischaemic area using multiple small injections
- Do not delay treatment while awaiting specialist consultation
Secondary Indications – Adults (Off-label, if any)
1. Erectile Dysfunction (Intracavernosal Use)
- Dose: 0.5–2.5 mg intracavernosally (usually in combination with papaverine)
- Duration: As needed; not more than once daily
- Specialist only: Yes — Urology
- OFF-LABEL
- Evidence basis: Pre-dates PDE5 inhibitors; now rarely used; historical use documented in specialist urology practice
2. Reversal of Dental Local Anaesthesia
- NOT AVAILABLE in India — Specific formulation (OraVerse) not marketed
- US FDA-approved indication but not applicable to Indian practice
PAEDIATRIC DOSING (Specialist Only)
Primary Indications (Approved / Standard in India)
Hypertensive Crisis in Phaeochromocytoma (Perioperative)
| Weight/Age | Dose | Maximum | Clinical Notes |
| All paediatric ages | 0.05–0.1 mg/kg IV | 5 mg per dose | Administer slowly over 1 minute |
| Repeat dosing | Every 4–6 hours as needed | — | Based on BP response |
Key Clinical Notes:
- Use only under paediatric endocrinologist or paediatric intensivist supervision
- Continuous cardiovascular monitoring essential
- No strict minimum age; use guided by clinical necessity
Secondary Indications – Paediatrics (Off-label, if any)
Vasopressor Extravasation
- Dose: 0.1 mg/kg (maximum 5 mg) diluted in normal saline
- Route: Local infiltration into affected area
- Duration: Single dose; repeat if clinical signs persist
- Specialist only: Yes — Paediatric Intensivist
- OFF-LABEL
- Evidence basis: Extrapolated from adult practice; case reports support efficacy
Statement: Not routinely used in children outside phaeochromocytoma or extravasation emergencies. All paediatric use requires specialist supervision.
RENAL ADJUSTMENT
| Renal Function | Recommendation |
| Mild to moderate impairment | No specific dose adjustment required |
| Severe impairment | Use with caution; monitor for prolonged hypotensive effect |
| Haemodialysis | No specific data; use cautiously with BP monitoring |
HEPATIC ADJUSTMENT
| Severity | Recommendation |
| Mild impairment | No dose adjustment; monitor cardiovascular response |
| Moderate impairment | Use with caution; monitor BP closely |
| Severe impairment | Use with caution; limited safety data available; specialist supervision advised |
CONTRAINDICATIONS
- Pre-existing hypotension or shock states
- Evidence of myocardial insufficiency or recent myocardial infarction
- Severe coronary artery disease
- Severe cerebrovascular atherosclerosis
- Known hypersensitivity to phentolamine or any excipient
CAUTIONS
- Coronary artery disease — risk of angina due to reflex tachycardia
- History of peptic ulcer disease — may stimulate gastric acid secretion
- Volume depletion or dehydration
- Elderly patients — increased sensitivity to hypotensive effects
- Concurrent use of other antihypertensive agents
- Tachyarrhythmias — may be exacerbated by reflex sympathetic activation
- Avoid abrupt discontinuation if used continuously — risk of rebound hypertension
PREGNANCY
| Parameter | Recommendation |
| Risk category | Limited human data; use only if clearly indicated |
| Overall safety | No adequate controlled studies; potential fetal risk unknown |
| Preferred alternatives | Labetalol, nifedipine for hypertension in pregnancy (Indian obstetric practice) |
| When to use | Short-term control of phaeochromocytoma crisis (specialist only) |
| Monitoring | Maternal BP, fetal heart rate, uteroplacental perfusion |
LACTATION
| Parameter | Recommendation |
| Compatibility | Unknown; exercise caution |
| Expected drug levels in milk | Unknown |
| Preferred alternatives | Labetalol, hydralazine (agents with established safety profile) |
| Infant monitoring | Signs of hypotension, feeding difficulties, lethargy |
ELDERLY
- Starting dose: Use lower end of dosing range (2.5 mg IV initially)
- Titration: Slower increments with careful BP monitoring
- Extra risks:
-
- Increased susceptibility to postural hypotension
- Higher fall risk
- May have underlying coronary or cerebrovascular disease
- Reduced renal reserve affecting drug clearance
- Monitoring: Continuous BP and HR during administration
MAJOR DRUG INTERACTIONS
| Interacting Drug | Effect | Recommendation |
| PDE5 inhibitors (sildenafil, tadalafil) | Severe additive hypotension | Avoid concurrent use |
| Other antihypertensives (beta-blockers, CCBs, ACE inhibitors) | Profound hypotension | Use with extreme caution; adjust doses |
| Adrenaline (epinephrine) | Paradoxical hypotension due to unopposed beta-2 vasodilation | Avoid; use noradrenaline or phenylephrine if pressor needed |
| MAO inhibitors | Unpredictable and severe BP changes | Avoid combination |
MODERATE DRUG INTERACTIONS
| Interacting Drug | Effect | Recommendation |
| NSAIDs | May attenuate hypotensive effect | Monitor BP; may need dose adjustment |
| Tricyclic antidepressants | Enhanced postural hypotension | Monitor closely; slower titration |
| Dopamine agonists/antagonists | Unpredictable BP response | Use cautiously; close monitoring |
| Alcohol | Additive hypotensive effect | Advise avoidance during treatment |
| Anaesthetic agents | Enhanced hypotension | Inform anaesthetist; dose adjustment may be needed |
COMMON ADVERSE EFFECTS
- Hypotension (dose-related)
- Reflex tachycardia
- Nasal congestion
- Flushing
- Dizziness
- Headache
- Nausea and vomiting
- Diarrhoea
SERIOUS ADVERSE EFFECTS
- Severe prolonged hypotension requiring vasopressor support
- Myocardial ischaemia or infarction (in patients with underlying CAD)
- Cardiac arrhythmias
- Cerebrovascular accident (in susceptible patients)
- Gastrointestinal bleeding (rare; related to gastric acid hypersecretion)
Action Required: Discontinue immediately if signs of myocardial ischaemia, severe hypotension unresponsive to fluids, or arrhythmias occur.
MONITORING REQUIREMENTS
| Phase | Parameters |
| Baseline | Blood pressure, heart rate, ECG (if cardiac disease suspected), renal function |
| During administration | Continuous BP and HR monitoring (invasive arterial line preferred in ICU setting) |
| After administration | Monitor BP for at least 30–60 minutes post-injection |
| For extravasation treatment | Monitor affected limb for perfusion, colour, temperature, capillary refill |
| Long-term (rare) | Cardiac status, GI symptoms if repeated use |
BRANDS AVAILABLE IN INDIA
- Regitine® Injection (Pfizer) — limited availability
- Generic phentolamine injections — available through hospital procurement channels
- Note: Primarily stocked in tertiary care centres; not routinely available in retail pharmacies
PRICE RANGE (INR)
- Approximate: ₹250–₹450 per 10 mg ampoule (private sector)
- NLEM status: Not listed under National List of Essential Medicines
- NPPA control: Not under price control
- Availability: Hospital supply predominantly; limited retail availability
CLINICAL PEARLS
- Reserve primarily for phaeochromocytoma-related hypertensive emergencies — not for routine hypertension management
- Reflex tachycardia is common; consider adding beta-blocker only after adequate alpha-blockade established
- Short duration of action (15–30 minutes) makes it suitable for acute management but impractical for chronic use
- For vasopressor extravasation, time is critical — administer within 12 hours for best outcomes; do not delay for specialist opinion
- Always have vasopressors (noradrenaline, phenylephrine) ready to manage excessive hypotension
- Intracavernosal use for erectile dysfunction is historical; replaced by safer PDE5 inhibitors in current practice
TAGS
phentolamine; alpha-blocker; phaeochromocytoma; hypertensive crisis; vasopressor extravasation; non-selective alpha antagonist; critical care; Regitine; Schedule H; India
VERSION
RxIndia v0.9 — 14 Feb 2026
REFERENCES
- CDSCO Formulation Database
- Indian Pharmacopoeia (IP 2018)
- API Textbook of Medicine
- AIIMS Pharmacology Department Protocols
- Goodman & Gilman’s The Pharmacological Basis of Therapeutics
- Harrison’s Principles of Internal Medicine
- Published case series for extravasation management (OFF-LABEL use)
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Clinical Responsibility
This platform is designed strictly for healthcare professionals. Data provided is synthesized from authoritative pharmacological sources and clinical registries. Do not use for consumer medical decisions. Always verify critical dosing and contraindications with official institutional protocols and peer-reviewed journals.
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