Pridinol (Myditin®)

Pridinol is a centrally and peripherally acting muscle relaxant marketed under the brand name Myditin®. It is used to treat acute painful muscle tension, particularly in cases of back and neck pain.

The active ingredient has both anticholinergic and antihistaminergic properties and relaxes muscles through several mechanisms. Pridinol has been used in Germany for decades.

It is usually prescribed as short-term therapy in combination with analgesics and physical therapy.

Pridinol works through several mechanisms:

Mechanisms of action:

• Anticholinergic: Inhibits cholinergic transmission at the motor end plate
• Centrally muscle-relaxing: Inhibits polysynaptic reflexes in the spinal cord
• Analgesic: Its own pain-relieving effect (via glutamate receptors)

Special features:

• Relaxes muscles both centrally and peripherally
• Has an independent pain-relieving effect
• Watch for anticholinergic side effects

Pharmacokinetics:

• Onset of action: 30–60 minutes
• Duration of action: 4–6 hours
• Half-life: approx. 4 hours

Pridinol is suitable for:

• Acute painful muscle tension
• Lumbago (sudden low back pain)
• Torticollis (acute wry neck)
• Painful muscle hardening in the back and neck area

Used as:

• Add-on medication alongside analgesics
• Short-term therapy (up to 2–3 weeks)
• A supplement to physical therapy

Not suitable:

• In narrow-angle glaucoma
• In prostate adenoma with residual urine formation
• In megacolon
• In myasthenia gravis

Tablets:

• 3 mg

Usual dosage (adults):

• ½ to 1 tablet 3 times daily (1.5–3 mg pridinol per dose)
• Recommended daily dose: 4.5–9 mg

Duration of treatment:

• Short-term: 1–3 weeks
• Not recommended for long-term use

How to take:

• Swallow the tablets whole with water
• With or without meals
• 3 times daily at regular intervals

Important notes:

• Your ability to drive may be impaired
• No alcohol (increased sedation)
• Caution in hot weather (anticholinergic → reduced sweat production)
• Counter dry mouth with water or sugar-free chewing gum

Pridinol must not be taken in case of:

• Glaucoma
• Enlarged prostate (prostatic hypertrophy)
• Conditions with urinary retention
• Narrowing or blockage of the gastrointestinal tract
• Heart rhythm disorders
• Pregnancy in the first trimester
• Hypersensitivity to pridinol or any of the other ingredients

Caution in case of:

• Tendency toward constipation
• Fever (reduced heat dissipation)
• Elderly patients (risk of falls, confusion)

Pregnancy/breastfeeding: Pridinol must not be taken during the first trimester of pregnancy. After that, only after careful medical assessment, under medical supervision and only if strictly necessary. Use during breastfeeding should be avoided.

Common (anticholinergic effects):

• Dry mouth
• Fatigue, drowsiness
• Accommodation disorders (impaired near vision)
• Constipation
• Urinary retention

Uncommon:

• Tachycardia (fast heartbeat)
• Gastrointestinal complaints
• Dizziness
• Confusion (especially in elderly patients)

Rare:

• Allergic skin reactions
• Glaucoma attack (in predisposed patients)

Note: The anticholinergic side effects limit its use in elderly patients.

Increased anticholinergic effect with:

• Tricyclic antidepressants
• Antihistamines
• Neuroleptics
• Antiparkinsonian drugs (e.g., biperiden)

Increased sedation with:

• Alcohol
• Benzodiazepines
• Opioids
• Antihistamines

Caution with:

• MAO inhibitors
• Other centrally acting medications