What are Muscle Relaxants?

Muscle relaxants are medications used to reduce muscle tension and relieve pain caused by muscle or tendon inflammation. In Thailand, they are commonly called "ya khlai sen" (เส้น = tendons) and are widely used for back pain and muscle tightness from prolonged sitting, heavy lifting, or improper exercise.

Mechanism of action

Muscle relaxants work through two main pathways:

• Centrally-acting (CNS) muscle relaxants — reduce nerve signals from the brain and spinal cord to the muscles, allowing them to relax. Most commonly used examples include Tolperisone, Eperisone, and Orphenadrine.
• Direct-acting muscle relaxants — such as Dantrolene, used less commonly in Thailand for severe muscle spasticity conditions.

Muscle relaxants are not pain killers by themselves — they relieve the muscle tightness that causes pain. Doctors typically prescribe them alongside pain relievers such as Paracetamol or NSAIDs for combined relief.

Statistics about Muscle Relaxants

Back pain and muscle ache are extremely common worldwide. The numbers below show why muscle relaxants are part of everyday healthcare:

Types of Muscle Relaxants

Muscle relaxants are divided into two major groups based on mechanism — used for clearly different conditions:

Antispasmodics (short-term use)

Used for muscle spasms from acute injury — e.g. acute back pain, neck strain, shoulder tension. The most commonly used group:

• Tolperisone — Mydocalm, Biocalm
• Eperisone — Myonal (least sedating)
• Orphenadrine — Norgesic (often combined with Paracetamol)
• Chlorzoxazone, Methocarbamol — less common in Thailand

Antispastics (long-term use)

Used for neurological conditions causing chronic muscle spasticity — e.g. stroke, multiple sclerosis, cerebral palsy. Must be used under medical supervision:

• Baclofen — spasticity from neurological disease
• Tizanidine — muscle spasticity
• Dantrolene — used rarely, only for malignant hyperthermia

📖 Read more: Want details on each drug — what is Tolperisone, who should use it? Read on at Types of Muscle Relaxants — Tolperisone, Orphenadrine, Eperisone — Which to use

What conditions are Muscle Relaxants used for?

Muscle relaxants are suitable for conditions caused by muscle or tendon tightness:

• Acute back pain — from heavy lifting, improper exercise, prolonged sitting
• Stiff neck / tight shoulders — from screen work, herniated disc, waking up with a kinked neck
• Myositis — swelling, pain, restricted movement
• Tendonitis — particularly wrists, elbows, knees
• Cramps — recurring from muscle fatigue or dehydration
• Recovery from sports injury — short-term use to help muscles relax faster

When NOT to use muscle relaxants

• Pain accompanied by high fever — possible infection, see a doctor
• Pain radiating down the leg with numbness — suspect nerve issue, not muscle
• Chronic pain longer than 2 weeks — needs further investigation
• Pain with weight loss, severe fatigue, fever — sign of serious illness

💡 Read more: Chronic back pain, tendonitis — which muscle relaxant works fastest? Read on at Muscle Relaxants for Back Pain and Tendonitis — How to use them for fast recovery

How to take Muscle Relaxants — before or after meals?

How to take muscle relaxants safely and effectively:

• Take immediately after meals — reduces stomach irritation, especially for those with sensitive stomachs
• Take 2-3 times per day — as labeled or prescribed; do not increase the dose yourself
• Onset within 30-60 minutes — gradual relaxation, not immediate pain relief like analgesics
• Short-term use, 5-7 days — if no improvement, see a doctor; do not continue indefinitely as it may cause dependence or tolerance
• Can be taken before bedtime — drowsiness side effect can help with sleep on painful nights

📖 Read more: Onset duration? Can you take with Paracetamol? What about pregnancy? Full answers at How to Take Muscle Relaxants — Before or After Meals? How long does it last?

Side Effects of Muscle Relaxants

Side effects are common because most muscle relaxants act on the central nervous system:

Warning signs — go to the hospital immediately

• ❗ Generalized rash, facial swelling, difficulty breathing (Anaphylaxis)
• ❗ Yellow skin/eyes, dark urine (drug-induced hepatitis — possible with Tolperisone)
• ❗ Severe heart rhythm abnormalities
• ❗ Seizures or loss of consciousness

Contraindications and Drug Interactions

Who should NOT use them?

• Anyone allergic to the specific drug
• Patients with severe liver or kidney disease
• Children under 12 years (unless prescribed by a doctor)
• Patients with Myasthenia gravis (autoimmune muscle weakness)

Groups requiring extra caution

• Pregnant women — most are Pregnancy Category C; always consult a doctor first
• Breastfeeding mothers — drugs pass into breast milk
• Elderly — risk of falls due to drowsiness and dizziness
• Drivers / heavy machinery operators — avoid use before work, or choose Eperisone (least sedating)

Drugs that should NOT be combined

• Alcohol — additive CNS depression; severe drowsiness, life-threatening
• Sedatives / sleeping pills (Benzodiazepines) — additive CNS depression
• Opioids (Tramadol, Codeine, Morphine) — risk of respiratory depression
• Older antihistamines (Chlorpheniramine) — combined drowsiness
• MAO Inhibitors (some antidepressants) — particularly with Orphenadrine

💡 Can be combined with Paracetamol — safe and standard practice (Norgesic itself is Orphenadrine + Paracetamol).

Muscle Relaxant Brands in Thailand — Which one to choose?

Several muscle relaxant brands are available in Thailand, each with different strengths and use cases — here are 4 popular options:

📖 Read more: Detailed brand comparison — Mydocalm vs Biocalm vs Myonal vs Norgesic, which gives the best value? Read on at Best Muscle Relaxant Brand — Comparing Norgesic, Mydocalm, Biocalm, Myonal

Where to buy muscle relaxants?

Most muscle relaxants in Thailand need pharmacist or doctor involvement, so ask a pharmacist before you choose. Intimo Life stocks the 4 popular brands available in Thailand across all 3 generic classes.

Mydocalm — Branded Tolperisone

The original Tolperisone brand from European manufacturers (Sanofi/Gedeon Richter), well-established and widely used in Thai medical practice for decades. It is the standard go-to choice doctors prescribe when quality Tolperisone is needed. Available in 50 mg and 150 mg to match symptom severity. Suitable for acute back pain, neck strain, and shoulder tension — relaxes muscles without strong sedation, less drowsy than other options in the class.

Biocalm — Affordable Tolperisone alternative

Tolperisone 50 mg manufactured in Thailand. Same active ingredient as Mydocalm, offered as a more affordable alternative. Ideal for those needing several days of treatment or who want to try Tolperisone before committing long-term. Pharmacological properties are equivalent to the original — packaged in blister strips for easy dosing as recommended by your pharmacist.

Myonal — Eperisone, least sedating

Eperisone 50 mg from Japanese manufacturer Eisai. The least sedating muscle relaxant among popular brands. It works through dual action — relaxing muscles AND improving local blood circulation through localized vasodilation. Particularly suited for office workers, drivers, and active elderly who must stay alert and mobile throughout the day — a premium option that does not disrupt your daily life.

Norgesic — Combined muscle relaxant + pain reliever

Orphenadrine 35 mg + Paracetamol 450 mg in a single tablet. A dual-action formula working on two fronts simultaneously — Orphenadrine relaxes muscles, Paracetamol relieves pain — convenient without needing to take two separate tablets. Suitable for acute pain requiring fast relief such as severe back pain, lower back strain, or neck pain from improper exercise form. Note: causes more drowsiness than other options, and do NOT take additional Paracetamol as it is already included in each tablet.

Consult a pharmacist online before ordering any of these to ensure your choice matches your symptoms, severity level, and any underlying conditions — current prices are shown on the product pages.

Real User Experiences

"I had back pain from sitting at work for 3 days straight and it wouldn't go away. I tried Mydocalm on the pharmacist's recommendation — 1 tablet after breakfast. By day 2 my back felt much looser, no more morning stiffness. Long sitting sessions were manageable again. Side effect was mild drowsiness, so I switched to taking it before bed instead. Cleared up in 5 days."

— A user with chronic back pain from desk work

"I had neck pain from working out with bad form. I chose Myonal because I drive to work every day. The doctor said Eperisone is the least sedating in the muscle relaxant class. After 3 days the pain improved. Slightly more expensive but worth it because I could work normally without drowsiness."

— A daily driver/commuter